From 1b430beee5e388605dfb092b214ef0320f752cf6 Mon Sep 17 00:00:00 2001 From: Wu Fengguang Date: Tue, 26 Oct 2010 14:21:26 -0700 Subject: writeback: remove nonblocking/encountered_congestion references This removes more dead code that was somehow missed by commit 0d99519efef (writeback: remove unused nonblocking and congestion checks). There are no behavior change except for the removal of two entries from one of the ext4 tracing interface. The nonblocking checks in ->writepages are no longer used because the flusher now prefer to block on get_request_wait() than to skip inodes on IO congestion. The latter will lead to more seeky IO. The nonblocking checks in ->writepage are no longer used because it's redundant with the WB_SYNC_NONE check. We no long set ->nonblocking in VM page out and page migration, because a) it's effectively redundant with WB_SYNC_NONE in current code b) it's old semantic of "Don't get stuck on request queues" is mis-behavior: that would skip some dirty inodes on congestion and page out others, which is unfair in terms of LRU age. Inspired by Christoph Hellwig. Thanks! Signed-off-by: Wu Fengguang Cc: Theodore Ts'o Cc: David Howells Cc: Sage Weil Cc: Steve French Cc: Chris Mason Cc: Jens Axboe Cc: Christoph Hellwig Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 1 - 1 file changed, 1 deletion(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index b94c9464f262..6cbc1aac23ae 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -376,7 +376,6 @@ static pageout_t pageout(struct page *page, struct address_space *mapping, .nr_to_write = SWAP_CLUSTER_MAX, .range_start = 0, .range_end = LLONG_MAX, - .nonblocking = 1, .for_reclaim = 1, }; -- cgit v1.2.2 From e4455abb50a19562dbfdc51a8424fda9b588bd6d Mon Sep 17 00:00:00 2001 From: Thadeu Lima de Souza Cascardo Date: Tue, 26 Oct 2010 14:21:28 -0700 Subject: mm: only build per-node scan_unevictable functions when NUMA is enabled Non-NUMA systems do never create these files anyway, since they are only created by driver subsystem when NUMA is configured. [akpm@linux-foundation.org: cleanup] Signed-off-by: Thadeu Lima de Souza Cascardo Reviewed-by: KOSAKI Motohiro Cc: Lee Schermerhorn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 6cbc1aac23ae..f5871ee50000 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2986,6 +2986,7 @@ int scan_unevictable_handler(struct ctl_table *table, int write, return 0; } +#ifdef CONFIG_NUMA /* * per node 'scan_unevictable_pages' attribute. On demand re-scan of * a specified node's per zone unevictable lists for evictable pages. @@ -3032,4 +3033,4 @@ void scan_unevictable_unregister_node(struct node *node) { sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); } - +#endif -- cgit v1.2.2 From 74e3f3c3391d81a959f58a1191a560703a4415b4 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Tue, 26 Oct 2010 14:21:31 -0700 Subject: vmscan: prevent background aging of anon page in no swap system Ying Han reported that backing aging of anon pages in no swap system causes unnecessary TLB flush. When I sent a patch(69c8548175), I wanted this patch but Rik pointed out and allowed aging of anon pages to give a chance to promote from inactive to active LRU. It has a two problem. 1) non-swap system Never make sense to age anon pages. 2) swap configured but still doesn't swapon It doesn't make sense to age anon pages until swap-on time. But it's arguable. If we have aged anon pages by swapon, VM have moved anon pages from active to inactive. And in the time swapon by admin, the VM can't reclaim hot pages so we can protect hot pages swapout. But let's think about it. When does swap-on happen? It depends on admin. we can't expect it. Nonetheless, we have done aging of anon pages to protect hot pages swapout. It means we lost run time overhead when below high watermark but gain hot page swap-[in/out] overhead when VM decide swapout. Is it true? Let's think more detail. We don't promote anon pages in case of non-swap system. So even though VM does aging of anon pages, the pages would be in inactive LRU for a long time. It means many of pages in there would mark access bit again. So access bit hot/code separation would be pointless. This patch prevents unnecessary anon pages demotion in not-yet-swapon and non-configured swap system. Even, in non-configuared swap system inactive_anon_is_low can be compiled out. It could make side effect that hot anon pages could swap out when admin does swap on. But I think sooner or later it would be steady state. So it's not a big problem. We could lose someting but gain more thing(TLB flush and unnecessary function call to demote anon pages). Signed-off-by: Ying Han Signed-off-by: Minchan Kim Reviewed-by: Rik van Riel Reviewed-by: KOSAKI Motohiro Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index f5871ee50000..0c33a0997907 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1505,6 +1505,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, spin_unlock_irq(&zone->lru_lock); } +#ifdef CONFIG_SWAP static int inactive_anon_is_low_global(struct zone *zone) { unsigned long active, inactive; @@ -1530,12 +1531,26 @@ static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) { int low; + /* + * If we don't have swap space, anonymous page deactivation + * is pointless. + */ + if (!total_swap_pages) + return 0; + if (scanning_global_lru(sc)) low = inactive_anon_is_low_global(zone); else low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); return low; } +#else +static inline int inactive_anon_is_low(struct zone *zone, + struct scan_control *sc) +{ + return 0; +} +#endif static int inactive_file_is_low_global(struct zone *zone) { @@ -1781,7 +1796,7 @@ static void shrink_zone(int priority, struct zone *zone, * Even if we did not try to evict anon pages at all, we want to * rebalance the anon lru active/inactive ratio. */ - if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0) + if (inactive_anon_is_low(zone, sc)) shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); throttle_vm_writeout(sc->gfp_mask); -- cgit v1.2.2 From 66d9a986cddbbc2ea5db013e7999c621a956cc47 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Tue, 26 Oct 2010 14:21:37 -0700 Subject: vmscan: delete dead code `priority' cannot be negative here. And the comment is obsolete. Signed-off-by: Shaohua Li Reviewed-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 10 ---------- 1 file changed, 10 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 0c33a0997907..28b0521e4bfd 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1956,16 +1956,6 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, } out: - /* - * Now that we've scanned all the zones at this priority level, note - * that level within the zone so that the next thread which performs - * scanning of this zone will immediately start out at this priority - * level. This affects only the decision whether or not to bring - * mapped pages onto the inactive list. - */ - if (priority < 0) - priority = 0; - delayacct_freepages_end(); put_mems_allowed(); -- cgit v1.2.2 From e11da5b4fdf01d71d73c21cb92b00595b917d7fd Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 26 Oct 2010 14:21:40 -0700 Subject: tracing, vmscan: add trace events for LRU list shrinking There have been numerous reports of stalls that pointed at the problem being somewhere in the VM. There are multiple roots to the problems which means dealing with any of the root problems in isolation is tricky to justify on their own and they would still need integration testing. This patch series puts together two different patch sets which in combination should tackle some of the root causes of latency problems being reported. Patch 1 adds a tracepoint for shrink_inactive_list. For this series, the most important results is being able to calculate the scanning/reclaim ratio as a measure of the amount of work being done by page reclaim. Patch 2 accounts for time spent in congestion_wait. Patches 3-6 were originally developed by Kosaki Motohiro but reworked for this series. It has been noted that lumpy reclaim is far too aggressive and trashes the system somewhat. As SLUB uses high-order allocations, a large cost incurred by lumpy reclaim will be noticeable. It was also reported during transparent hugepage support testing that lumpy reclaim was trashing the system and these patches should mitigate that problem without disabling lumpy reclaim. Patch 7 adds wait_iff_congested() and replaces some callers of congestion_wait(). wait_iff_congested() only sleeps if there is a BDI that is currently congested. Patch 8 notes that any BDI being congested is not necessarily a problem because there could be multiple BDIs of varying speeds and numberous zones. It attempts to track when a zone being reclaimed contains many pages backed by a congested BDI and if so, reclaimers wait on the congestion queue. I ran a number of tests with monitoring on X86, X86-64 and PPC64. Each machine had 3G of RAM and the CPUs were X86: Intel P4 2-core X86-64: AMD Phenom 4-core PPC64: PPC970MP Each used a single disk and the onboard IO controller. Dirty ratio was left at 20. I'm just going to report for X86-64 and PPC64 in a vague attempt to keep this report short. Four kernels were tested each based on v2.6.36-rc4 traceonly-v2r2: Patches 1 and 2 to instrument vmscan reclaims and congestion_wait lowlumpy-v2r3: Patches 1-6 to test if lumpy reclaim is better waitcongest-v2r3: Patches 1-7 to only wait on congestion waitwriteback-v2r4: Patches 1-8 to detect when a zone is congested nocongest-v1r5: Patches 1-3 for testing wait_iff_congestion nodirect-v1r5: Patches 1-10 to disable filesystem writeback for better IO The tests run were as follows kernbench compile-based benchmark. Smoke test performance sysbench OLTP read-only benchmark. Will be re-run in the future as read-write micro-mapped-file-stream This is a micro-benchmark from Johannes Weiner that accesses a large sparse-file through mmap(). It was configured to run in only single-CPU mode but can be indicative of how well page reclaim identifies suitable pages. stress-highalloc Tries to allocate huge pages under heavy load. kernbench, iozone and sysbench did not report any performance regression on any machine. sysbench did pressure the system lightly and there was reclaim activity but there were no difference of major interest between the kernels. X86-64 micro-mapped-file-stream traceonly-v2r2 lowlumpy-v2r3 waitcongest-v2r3 waitwriteback-v2r4 pgalloc_dma 1639.00 ( 0.00%) 667.00 (-145.73%) 1167.00 ( -40.45%) 578.00 (-183.56%) pgalloc_dma32 2842410.00 ( 0.00%) 2842626.00 ( 0.01%) 2843043.00 ( 0.02%) 2843014.00 ( 0.02%) pgalloc_normal 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) pgsteal_dma 729.00 ( 0.00%) 85.00 (-757.65%) 609.00 ( -19.70%) 125.00 (-483.20%) pgsteal_dma32 2338721.00 ( 0.00%) 2447354.00 ( 4.44%) 2429536.00 ( 3.74%) 2436772.00 ( 4.02%) pgsteal_normal 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) pgscan_kswapd_dma 1469.00 ( 0.00%) 532.00 (-176.13%) 1078.00 ( -36.27%) 220.00 (-567.73%) pgscan_kswapd_dma32 4597713.00 ( 0.00%) 4503597.00 ( -2.09%) 4295673.00 ( -7.03%) 3891686.00 ( -18.14%) pgscan_kswapd_normal 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) pgscan_direct_dma 71.00 ( 0.00%) 134.00 ( 47.01%) 243.00 ( 70.78%) 352.00 ( 79.83%) pgscan_direct_dma32 305820.00 ( 0.00%) 280204.00 ( -9.14%) 600518.00 ( 49.07%) 957485.00 ( 68.06%) pgscan_direct_normal 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) pageoutrun 16296.00 ( 0.00%) 21254.00 ( 23.33%) 18447.00 ( 11.66%) 20067.00 ( 18.79%) allocstall 443.00 ( 0.00%) 273.00 ( -62.27%) 513.00 ( 13.65%) 1568.00 ( 71.75%) These are based on the raw figures taken from /proc/vmstat. It's a rough measure of reclaim activity. Note that allocstall counts are higher because we are entering direct reclaim more often as a result of not sleeping in congestion. In itself, it's not necessarily a bad thing. It's easier to get a view of what happened from the vmscan tracepoint report. FTrace Reclaim Statistics: vmscan traceonly-v2r2 lowlumpy-v2r3 waitcongest-v2r3 waitwriteback-v2r4 Direct reclaims 443 273 513 1568 Direct reclaim pages scanned 305968 280402 600825 957933 Direct reclaim pages reclaimed 43503 19005 30327 117191 Direct reclaim write file async I/O 0 0 0 0 Direct reclaim write anon async I/O 0 3 4 12 Direct reclaim write file sync I/O 0 0 0 0 Direct reclaim write anon sync I/O 0 0 0 0 Wake kswapd requests 187649 132338 191695 267701 Kswapd wakeups 3 1 4 1 Kswapd pages scanned 4599269 4454162 4296815 3891906 Kswapd pages reclaimed 2295947 2428434 2399818 2319706 Kswapd reclaim write file async I/O 1 0 1 1 Kswapd reclaim write anon async I/O 59 187 41 222 Kswapd reclaim write file sync I/O 0 0 0 0 Kswapd reclaim write anon sync I/O 0 0 0 0 Time stalled direct reclaim (seconds) 4.34 2.52 6.63 2.96 Time kswapd awake (seconds) 11.15 10.25 11.01 10.19 Total pages scanned 4905237 4734564 4897640 4849839 Total pages reclaimed 2339450 2447439 2430145 2436897 %age total pages scanned/reclaimed 47.69% 51.69% 49.62% 50.25% %age total pages scanned/written 0.00% 0.00% 0.00% 0.00% %age file pages scanned/written 0.00% 0.00% 0.00% 0.00% Percentage Time Spent Direct Reclaim 29.23% 19.02% 38.48% 20.25% Percentage Time kswapd Awake 78.58% 78.85% 76.83% 79.86% What is interesting here for nocongest in particular is that while direct reclaim scans more pages, the overall number of pages scanned remains the same and the ratio of pages scanned to pages reclaimed is more or less the same. In other words, while we are sleeping less, reclaim is not doing more work and as direct reclaim and kswapd is awake for less time, it would appear to be doing less work. FTrace Reclaim Statistics: congestion_wait Direct number congest waited 87 196 64 0 Direct time congest waited 4604ms 4732ms 5420ms 0ms Direct full congest waited 72 145 53 0 Direct number conditional waited 0 0 324 1315 Direct time conditional waited 0ms 0ms 0ms 0ms Direct full conditional waited 0 0 0 0 KSwapd number congest waited 20 10 15 7 KSwapd time congest waited 1264ms 536ms 884ms 284ms KSwapd full congest waited 10 4 6 2 KSwapd number conditional waited 0 0 0 0 KSwapd time conditional waited 0ms 0ms 0ms 0ms KSwapd full conditional waited 0 0 0 0 The vanilla kernel spent 8 seconds asleep in direct reclaim and no time at all asleep with the patches. MMTests Statistics: duration User/Sys Time Running Test (seconds) 10.51 10.73 10.6 11.66 Total Elapsed Time (seconds) 14.19 13.00 14.33 12.76 Overall, the tests completed faster. It is interesting to note that backing off further when a zone is congested and not just a BDI was more efficient overall. PPC64 micro-mapped-file-stream pgalloc_dma 3024660.00 ( 0.00%) 3027185.00 ( 0.08%) 3025845.00 ( 0.04%) 3026281.00 ( 0.05%) pgalloc_normal 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) pgsteal_dma 2508073.00 ( 0.00%) 2565351.00 ( 2.23%) 2463577.00 ( -1.81%) 2532263.00 ( 0.96%) pgsteal_normal 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) pgscan_kswapd_dma 4601307.00 ( 0.00%) 4128076.00 ( -11.46%) 3912317.00 ( -17.61%) 3377165.00 ( -36.25%) pgscan_kswapd_normal 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) pgscan_direct_dma 629825.00 ( 0.00%) 971622.00 ( 35.18%) 1063938.00 ( 40.80%) 1711935.00 ( 63.21%) pgscan_direct_normal 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) 0.00 ( 0.00%) pageoutrun 27776.00 ( 0.00%) 20458.00 ( -35.77%) 18763.00 ( -48.04%) 18157.00 ( -52.98%) allocstall 977.00 ( 0.00%) 2751.00 ( 64.49%) 2098.00 ( 53.43%) 5136.00 ( 80.98%) Similar trends to x86-64. allocstalls are up but it's not necessarily bad. FTrace Reclaim Statistics: vmscan Direct reclaims 977 2709 2098 5136 Direct reclaim pages scanned 629825 963814 1063938 1711935 Direct reclaim pages reclaimed 75550 242538 150904 387647 Direct reclaim write file async I/O 0 0 0 2 Direct reclaim write anon async I/O 0 10 0 4 Direct reclaim write file sync I/O 0 0 0 0 Direct reclaim write anon sync I/O 0 0 0 0 Wake kswapd requests 392119 1201712 571935 571921 Kswapd wakeups 3 2 3 3 Kswapd pages scanned 4601307 4128076 3912317 3377165 Kswapd pages reclaimed 2432523 2318797 2312673 2144616 Kswapd reclaim write file async I/O 20 1 1 1 Kswapd reclaim write anon async I/O 57 132 11 121 Kswapd reclaim write file sync I/O 0 0 0 0 Kswapd reclaim write anon sync I/O 0 0 0 0 Time stalled direct reclaim (seconds) 6.19 7.30 13.04 10.88 Time kswapd awake (seconds) 21.73 26.51 25.55 23.90 Total pages scanned 5231132 5091890 4976255 5089100 Total pages reclaimed 2508073 2561335 2463577 2532263 %age total pages scanned/reclaimed 47.95% 50.30% 49.51% 49.76% %age total pages scanned/written 0.00% 0.00% 0.00% 0.00% %age file pages scanned/written 0.00% 0.00% 0.00% 0.00% Percentage Time Spent Direct Reclaim 18.89% 20.65% 32.65% 27.65% Percentage Time kswapd Awake 72.39% 80.68% 78.21% 77.40% Again, a similar trend that the congestion_wait changes mean that direct reclaim scans more pages but the overall number of pages scanned while slightly reduced, are very similar. The ratio of scanning/reclaimed remains roughly similar. The downside is that kswapd and direct reclaim was awake longer and for a larger percentage of the overall workload. It's possible there were big differences in the amount of time spent reclaiming slab pages between the different kernels which is plausible considering that the micro tests runs after fsmark and sysbench. Trace Reclaim Statistics: congestion_wait Direct number congest waited 845 1312 104 0 Direct time congest waited 19416ms 26560ms 7544ms 0ms Direct full congest waited 745 1105 72 0 Direct number conditional waited 0 0 1322 2935 Direct time conditional waited 0ms 0ms 12ms 312ms Direct full conditional waited 0 0 0 3 KSwapd number congest waited 39 102 75 63 KSwapd time congest waited 2484ms 6760ms 5756ms 3716ms KSwapd full congest waited 20 48 46 25 KSwapd number conditional waited 0 0 0 0 KSwapd time conditional waited 0ms 0ms 0ms 0ms KSwapd full conditional waited 0 0 0 0 The vanilla kernel spent 20 seconds asleep in direct reclaim and only 312ms asleep with the patches. The time kswapd spent congest waited was also reduced by a large factor. MMTests Statistics: duration ser/Sys Time Running Test (seconds) 26.58 28.05 26.9 28.47 Total Elapsed Time (seconds) 30.02 32.86 32.67 30.88 With all patches applies, the completion times are very similar. X86-64 STRESS-HIGHALLOC traceonly-v2r2 lowlumpy-v2r3 waitcongest-v2r3waitwriteback-v2r4 Pass 1 82.00 ( 0.00%) 84.00 ( 2.00%) 85.00 ( 3.00%) 85.00 ( 3.00%) Pass 2 90.00 ( 0.00%) 87.00 (-3.00%) 88.00 (-2.00%) 89.00 (-1.00%) At Rest 92.00 ( 0.00%) 90.00 (-2.00%) 90.00 (-2.00%) 91.00 (-1.00%) Success figures across the board are broadly similar. traceonly-v2r2 lowlumpy-v2r3 waitcongest-v2r3waitwriteback-v2r4 Direct reclaims 1045 944 886 887 Direct reclaim pages scanned 135091 119604 109382 101019 Direct reclaim pages reclaimed 88599 47535 47863 46671 Direct reclaim write file async I/O 494 283 465 280 Direct reclaim write anon async I/O 29357 13710 16656 13462 Direct reclaim write file sync I/O 154 2 2 3 Direct reclaim write anon sync I/O 14594 571 509 561 Wake kswapd requests 7491 933 872 892 Kswapd wakeups 814 778 731 780 Kswapd pages scanned 7290822 15341158 11916436 13703442 Kswapd pages reclaimed 3587336 3142496 3094392 3187151 Kswapd reclaim write file async I/O 91975 32317 28022 29628 Kswapd reclaim write anon async I/O 1992022 789307 829745 849769 Kswapd reclaim write file sync I/O 0 0 0 0 Kswapd reclaim write anon sync I/O 0 0 0 0 Time stalled direct reclaim (seconds) 4588.93 2467.16 2495.41 2547.07 Time kswapd awake (seconds) 2497.66 1020.16 1098.06 1176.82 Total pages scanned 7425913 15460762 12025818 13804461 Total pages reclaimed 3675935 3190031 3142255 3233822 %age total pages scanned/reclaimed 49.50% 20.63% 26.13% 23.43% %age total pages scanned/written 28.66% 5.41% 7.28% 6.47% %age file pages scanned/written 1.25% 0.21% 0.24% 0.22% Percentage Time Spent Direct Reclaim 57.33% 42.15% 42.41% 42.99% Percentage Time kswapd Awake 43.56% 27.87% 29.76% 31.25% Scanned/reclaimed ratios again look good with big improvements in efficiency. The Scanned/written ratios also look much improved. With a better scanned/written ration, there is an expectation that IO would be more efficient and indeed, the time spent in direct reclaim is much reduced by the full series and kswapd spends a little less time awake. Overall, indications here are that allocations were happening much faster and this can be seen with a graph of the latency figures as the allocations were taking place http://www.csn.ul.ie/~mel/postings/vmscanreduce-20101509/highalloc-interlatency-hydra-mean.ps FTrace Reclaim Statistics: congestion_wait Direct number congest waited 1333 204 169 4 Direct time congest waited 78896ms 8288ms 7260ms 200ms Direct full congest waited 756 92 69 2 Direct number conditional waited 0 0 26 186 Direct time conditional waited 0ms 0ms 0ms 2504ms Direct full conditional waited 0 0 0 25 KSwapd number congest waited 4 395 227 282 KSwapd time congest waited 384ms 25136ms 10508ms 18380ms KSwapd full congest waited 3 232 98 176 KSwapd number conditional waited 0 0 0 0 KSwapd time conditional waited 0ms 0ms 0ms 0ms KSwapd full conditional waited 0 0 0 0 KSwapd full conditional waited 318 0 312 9 Overall, the time spent speeping is reduced. kswapd is still hitting congestion_wait() but that is because there are callers remaining where it wasn't clear in advance if they should be changed to wait_iff_congested() or not. Overall the sleep imes are reduced though - from 79ish seconds to about 19. MMTests Statistics: duration User/Sys Time Running Test (seconds) 3415.43 3386.65 3388.39 3377.5 Total Elapsed Time (seconds) 5733.48 3660.33 3689.41 3765.39 With the full series, the time to complete the tests are reduced by 30% PPC64 STRESS-HIGHALLOC traceonly-v2r2 lowlumpy-v2r3 waitcongest-v2r3waitwriteback-v2r4 Pass 1 17.00 ( 0.00%) 34.00 (17.00%) 38.00 (21.00%) 43.00 (26.00%) Pass 2 25.00 ( 0.00%) 37.00 (12.00%) 42.00 (17.00%) 46.00 (21.00%) At Rest 49.00 ( 0.00%) 43.00 (-6.00%) 45.00 (-4.00%) 51.00 ( 2.00%) Success rates there are *way* up particularly considering that the 16MB huge pages on PPC64 mean that it's always much harder to allocate them. FTrace Reclaim Statistics: vmscan stress-highalloc stress-highalloc stress-highalloc stress-highalloc traceonly-v2r2 lowlumpy-v2r3 waitcongest-v2r3waitwriteback-v2r4 Direct reclaims 499 505 564 509 Direct reclaim pages scanned 223478 41898 51818 45605 Direct reclaim pages reclaimed 137730 21148 27161 23455 Direct reclaim write file async I/O 399 136 162 136 Direct reclaim write anon async I/O 46977 2865 4686 3998 Direct reclaim write file sync I/O 29 0 1 3 Direct reclaim write anon sync I/O 31023 159 237 239 Wake kswapd requests 420 351 360 326 Kswapd wakeups 185 294 249 277 Kswapd pages scanned 15703488 16392500 17821724 17598737 Kswapd pages reclaimed 5808466 2908858 3139386 3145435 Kswapd reclaim write file async I/O 159938 18400 18717 13473 Kswapd reclaim write anon async I/O 3467554 228957 322799 234278 Kswapd reclaim write file sync I/O 0 0 0 0 Kswapd reclaim write anon sync I/O 0 0 0 0 Time stalled direct reclaim (seconds) 9665.35 1707.81 2374.32 1871.23 Time kswapd awake (seconds) 9401.21 1367.86 1951.75 1328.88 Total pages scanned 15926966 16434398 17873542 17644342 Total pages reclaimed 5946196 2930006 3166547 3168890 %age total pages scanned/reclaimed 37.33% 17.83% 17.72% 17.96% %age total pages scanned/written 23.27% 1.52% 1.94% 1.43% %age file pages scanned/written 1.01% 0.11% 0.11% 0.08% Percentage Time Spent Direct Reclaim 44.55% 35.10% 41.42% 36.91% Percentage Time kswapd Awake 86.71% 43.58% 52.67% 41.14% While the scanning rates are slightly up, the scanned/reclaimed and scanned/written figures are much improved. The time spent in direct reclaim and with kswapd are massively reduced, mostly by the lowlumpy patches. FTrace Reclaim Statistics: congestion_wait Direct number congest waited 725 303 126 3 Direct time congest waited 45524ms 9180ms 5936ms 300ms Direct full congest waited 487 190 52 3 Direct number conditional waited 0 0 200 301 Direct time conditional waited 0ms 0ms 0ms 1904ms Direct full conditional waited 0 0 0 19 KSwapd number congest waited 0 2 23 4 KSwapd time congest waited 0ms 200ms 420ms 404ms KSwapd full congest waited 0 2 2 4 KSwapd number conditional waited 0 0 0 0 KSwapd time conditional waited 0ms 0ms 0ms 0ms KSwapd full conditional waited 0 0 0 0 Not as dramatic a story here but the time spent asleep is reduced and we can still see what wait_iff_congested is going to sleep when necessary. MMTests Statistics: duration User/Sys Time Running Test (seconds) 12028.09 3157.17 3357.79 3199.16 Total Elapsed Time (seconds) 10842.07 3138.72 3705.54 3229.85 The time to complete this test goes way down. With the full series, we are allocating over twice the number of huge pages in 30% of the time and there is a corresponding impact on the allocation latency graph available at. http://www.csn.ul.ie/~mel/postings/vmscanreduce-20101509/highalloc-interlatency-powyah-mean.ps This patch: Add a trace event for shrink_inactive_list() and updates the sample postprocessing script appropriately. It can be used to determine how many pages were reclaimed and for non-lumpy reclaim where exactly the pages were reclaimed from. Signed-off-by: Mel Gorman Cc: Johannes Weiner Cc: Minchan Kim Cc: Wu Fengguang Cc: KAMEZAWA Hiroyuki Cc: KOSAKI Motohiro Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 28b0521e4bfd..4a6dccb57586 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1358,6 +1358,12 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); + + trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, + zone_idx(zone), + nr_scanned, nr_reclaimed, + priority, + trace_shrink_flags(file, sc->lumpy_reclaim_mode)); return nr_reclaimed; } -- cgit v1.2.2 From bc57e00f5e0b2480ef222c775c49552d3a930db7 Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Tue, 26 Oct 2010 14:21:41 -0700 Subject: vmscan: synchronous lumpy reclaim should not call congestion_wait() congestion_wait() means "wait until queue congestion is cleared". However, synchronous lumpy reclaim does not need this congestion_wait() as shrink_page_list(PAGEOUT_IO_SYNC) uses wait_on_page_writeback() and it provides the necessary waiting. Signed-off-by: KOSAKI Motohiro Signed-off-by: Mel Gorman Reviewed-by: Minchan Kim Reviewed-by: Johannes Weiner Reviewed-by: Wu Fengguang Reviewed-by: KAMEZAWA Hiroyuki Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 4a6dccb57586..399d54e8a82c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1340,8 +1340,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, /* Check if we should syncronously wait for writeback */ if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { - congestion_wait(BLK_RW_ASYNC, HZ/10); - /* * The attempt at page out may have made some * of the pages active, mark them inactive again. -- cgit v1.2.2 From 7d3579e8e61937cbba268ea9b218d006b6d64221 Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Tue, 26 Oct 2010 14:21:42 -0700 Subject: vmscan: narrow the scenarios in whcih lumpy reclaim uses synchrounous reclaim shrink_page_list() can decide to give up reclaiming a page under a number of conditions such as 1. trylock_page() failure 2. page is unevictable 3. zone reclaim and page is mapped 4. PageWriteback() is true 5. page is swapbacked and swap is full 6. add_to_swap() failure 7. page is dirty and gfpmask don't have GFP_IO, GFP_FS 8. page is pinned 9. IO queue is congested 10. pageout() start IO, but not finished With lumpy reclaim, failures result in entering synchronous lumpy reclaim but this can be unnecessary. In cases (2), (3), (5), (6), (7) and (8), there is no point retrying. This patch causes lumpy reclaim to abort when it is known it will fail. Case (9) is more interesting. current behavior is, 1. start shrink_page_list(async) 2. found queue_congested() 3. skip pageout write 4. still start shrink_page_list(sync) 5. wait on a lot of pages 6. again, found queue_congested() 7. give up pageout write again So, it's useless time wasting. However, just skipping page reclaim is also notgood as x86 allocating a huge page needs 512 pages for example. It can have more dirty pages than queue congestion threshold (~=128). After this patch, pageout() behaves as follows; - If order > PAGE_ALLOC_COSTLY_ORDER Ignore queue congestion always. - If order <= PAGE_ALLOC_COSTLY_ORDER skip write page and disable lumpy reclaim. Signed-off-by: KOSAKI Motohiro Signed-off-by: Mel Gorman Reviewed-by: KAMEZAWA Hiroyuki Cc: Johannes Weiner Cc: Minchan Kim Cc: Wu Fengguang Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 120 +++++++++++++++++++++++++++++++++++++----------------------- 1 file changed, 75 insertions(+), 45 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 399d54e8a82c..d9fc2dce93af 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -51,6 +51,12 @@ #define CREATE_TRACE_POINTS #include +enum lumpy_mode { + LUMPY_MODE_NONE, + LUMPY_MODE_ASYNC, + LUMPY_MODE_SYNC, +}; + struct scan_control { /* Incremented by the number of inactive pages that were scanned */ unsigned long nr_scanned; @@ -82,7 +88,7 @@ struct scan_control { * Intend to reclaim enough continuous memory rather than reclaim * enough amount of memory. i.e, mode for high order allocation. */ - bool lumpy_reclaim_mode; + enum lumpy_mode lumpy_reclaim_mode; /* Which cgroup do we reclaim from */ struct mem_cgroup *mem_cgroup; @@ -265,6 +271,36 @@ unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, return ret; } +static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc, + bool sync) +{ + enum lumpy_mode mode = sync ? LUMPY_MODE_SYNC : LUMPY_MODE_ASYNC; + + /* + * Some reclaim have alredy been failed. No worth to try synchronous + * lumpy reclaim. + */ + if (sync && sc->lumpy_reclaim_mode == LUMPY_MODE_NONE) + return; + + /* + * If we need a large contiguous chunk of memory, or have + * trouble getting a small set of contiguous pages, we + * will reclaim both active and inactive pages. + */ + if (sc->order > PAGE_ALLOC_COSTLY_ORDER) + sc->lumpy_reclaim_mode = mode; + else if (sc->order && priority < DEF_PRIORITY - 2) + sc->lumpy_reclaim_mode = mode; + else + sc->lumpy_reclaim_mode = LUMPY_MODE_NONE; +} + +static void disable_lumpy_reclaim_mode(struct scan_control *sc) +{ + sc->lumpy_reclaim_mode = LUMPY_MODE_NONE; +} + static inline int is_page_cache_freeable(struct page *page) { /* @@ -275,7 +311,8 @@ static inline int is_page_cache_freeable(struct page *page) return page_count(page) - page_has_private(page) == 2; } -static int may_write_to_queue(struct backing_dev_info *bdi) +static int may_write_to_queue(struct backing_dev_info *bdi, + struct scan_control *sc) { if (current->flags & PF_SWAPWRITE) return 1; @@ -283,6 +320,10 @@ static int may_write_to_queue(struct backing_dev_info *bdi) return 1; if (bdi == current->backing_dev_info) return 1; + + /* lumpy reclaim for hugepage often need a lot of write */ + if (sc->order > PAGE_ALLOC_COSTLY_ORDER) + return 1; return 0; } @@ -307,12 +348,6 @@ static void handle_write_error(struct address_space *mapping, unlock_page(page); } -/* Request for sync pageout. */ -enum pageout_io { - PAGEOUT_IO_ASYNC, - PAGEOUT_IO_SYNC, -}; - /* possible outcome of pageout() */ typedef enum { /* failed to write page out, page is locked */ @@ -330,7 +365,7 @@ typedef enum { * Calls ->writepage(). */ static pageout_t pageout(struct page *page, struct address_space *mapping, - enum pageout_io sync_writeback) + struct scan_control *sc) { /* * If the page is dirty, only perform writeback if that write @@ -366,8 +401,10 @@ static pageout_t pageout(struct page *page, struct address_space *mapping, } if (mapping->a_ops->writepage == NULL) return PAGE_ACTIVATE; - if (!may_write_to_queue(mapping->backing_dev_info)) + if (!may_write_to_queue(mapping->backing_dev_info, sc)) { + disable_lumpy_reclaim_mode(sc); return PAGE_KEEP; + } if (clear_page_dirty_for_io(page)) { int res; @@ -393,7 +430,8 @@ static pageout_t pageout(struct page *page, struct address_space *mapping, * direct reclaiming a large contiguous area and the * first attempt to free a range of pages fails. */ - if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC) + if (PageWriteback(page) && + sc->lumpy_reclaim_mode == LUMPY_MODE_SYNC) wait_on_page_writeback(page); if (!PageWriteback(page)) { @@ -401,7 +439,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping, ClearPageReclaim(page); } trace_mm_vmscan_writepage(page, - trace_reclaim_flags(page, sync_writeback)); + trace_reclaim_flags(page, sc->lumpy_reclaim_mode)); inc_zone_page_state(page, NR_VMSCAN_WRITE); return PAGE_SUCCESS; } @@ -579,7 +617,7 @@ static enum page_references page_check_references(struct page *page, referenced_page = TestClearPageReferenced(page); /* Lumpy reclaim - ignore references */ - if (sc->lumpy_reclaim_mode) + if (sc->lumpy_reclaim_mode != LUMPY_MODE_NONE) return PAGEREF_RECLAIM; /* @@ -643,8 +681,7 @@ static noinline_for_stack void free_page_list(struct list_head *free_pages) * shrink_page_list() returns the number of reclaimed pages */ static unsigned long shrink_page_list(struct list_head *page_list, - struct scan_control *sc, - enum pageout_io sync_writeback) + struct scan_control *sc) { LIST_HEAD(ret_pages); LIST_HEAD(free_pages); @@ -693,10 +730,13 @@ static unsigned long shrink_page_list(struct list_head *page_list, * for any page for which writeback has already * started. */ - if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs) + if (sc->lumpy_reclaim_mode == LUMPY_MODE_SYNC && + may_enter_fs) wait_on_page_writeback(page); - else - goto keep_locked; + else { + unlock_page(page); + goto keep_lumpy; + } } references = page_check_references(page, sc); @@ -750,14 +790,17 @@ static unsigned long shrink_page_list(struct list_head *page_list, goto keep_locked; /* Page is dirty, try to write it out here */ - switch (pageout(page, mapping, sync_writeback)) { + switch (pageout(page, mapping, sc)) { case PAGE_KEEP: goto keep_locked; case PAGE_ACTIVATE: goto activate_locked; case PAGE_SUCCESS: - if (PageWriteback(page) || PageDirty(page)) + if (PageWriteback(page)) + goto keep_lumpy; + if (PageDirty(page)) goto keep; + /* * A synchronous write - probably a ramdisk. Go * ahead and try to reclaim the page. @@ -840,6 +883,7 @@ cull_mlocked: try_to_free_swap(page); unlock_page(page); putback_lru_page(page); + disable_lumpy_reclaim_mode(sc); continue; activate_locked: @@ -852,6 +896,8 @@ activate_locked: keep_locked: unlock_page(page); keep: + disable_lumpy_reclaim_mode(sc); +keep_lumpy: list_add(&page->lru, &ret_pages); VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); } @@ -1252,7 +1298,7 @@ static inline bool should_reclaim_stall(unsigned long nr_taken, return false; /* Only stall on lumpy reclaim */ - if (!sc->lumpy_reclaim_mode) + if (sc->lumpy_reclaim_mode == LUMPY_MODE_NONE) return false; /* If we have relaimed everything on the isolated list, no stall */ @@ -1297,15 +1343,15 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, return SWAP_CLUSTER_MAX; } - + set_lumpy_reclaim_mode(priority, sc, false); lru_add_drain(); spin_lock_irq(&zone->lru_lock); if (scanning_global_lru(sc)) { nr_taken = isolate_pages_global(nr_to_scan, &page_list, &nr_scanned, sc->order, - sc->lumpy_reclaim_mode ? - ISOLATE_BOTH : ISOLATE_INACTIVE, + sc->lumpy_reclaim_mode == LUMPY_MODE_NONE ? + ISOLATE_INACTIVE : ISOLATE_BOTH, zone, 0, file); zone->pages_scanned += nr_scanned; if (current_is_kswapd()) @@ -1317,8 +1363,8 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, } else { nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list, &nr_scanned, sc->order, - sc->lumpy_reclaim_mode ? - ISOLATE_BOTH : ISOLATE_INACTIVE, + sc->lumpy_reclaim_mode == LUMPY_MODE_NONE ? + ISOLATE_INACTIVE : ISOLATE_BOTH, zone, sc->mem_cgroup, 0, file); /* @@ -1336,7 +1382,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, spin_unlock_irq(&zone->lru_lock); - nr_reclaimed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC); + nr_reclaimed = shrink_page_list(&page_list, sc); /* Check if we should syncronously wait for writeback */ if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { @@ -1347,7 +1393,8 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, nr_active = clear_active_flags(&page_list, NULL); count_vm_events(PGDEACTIVATE, nr_active); - nr_reclaimed += shrink_page_list(&page_list, sc, PAGEOUT_IO_SYNC); + set_lumpy_reclaim_mode(priority, sc, true); + nr_reclaimed += shrink_page_list(&page_list, sc); } local_irq_disable(); @@ -1739,21 +1786,6 @@ out: } } -static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc) -{ - /* - * If we need a large contiguous chunk of memory, or have - * trouble getting a small set of contiguous pages, we - * will reclaim both active and inactive pages. - */ - if (sc->order > PAGE_ALLOC_COSTLY_ORDER) - sc->lumpy_reclaim_mode = 1; - else if (sc->order && priority < DEF_PRIORITY - 2) - sc->lumpy_reclaim_mode = 1; - else - sc->lumpy_reclaim_mode = 0; -} - /* * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. */ @@ -1768,8 +1800,6 @@ static void shrink_zone(int priority, struct zone *zone, get_scan_count(zone, sc, nr, priority); - set_lumpy_reclaim_mode(priority, sc); - while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || nr[LRU_INACTIVE_FILE]) { for_each_evictable_lru(l) { -- cgit v1.2.2 From 47185052165a4c5de0a461018238375dd982c2ec Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Tue, 26 Oct 2010 14:21:43 -0700 Subject: vmscan: remove dead code in shrink_inactive_list() After synchrounous lumpy reclaim, the page_list is guaranteed to not have active pages as page activation in shrink_page_list() disables lumpy reclaim. Remove the dead code. Signed-off-by: KOSAKI Motohiro Signed-off-by: Mel Gorman Reviewed-by: Minchan Kim Cc: Johannes Weiner Cc: Wu Fengguang Cc: Rik van Riel Cc: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 8 -------- 1 file changed, 8 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index d9fc2dce93af..cec8081bbd95 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1331,7 +1331,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, unsigned long nr_scanned; unsigned long nr_reclaimed = 0; unsigned long nr_taken; - unsigned long nr_active; unsigned long nr_anon; unsigned long nr_file; @@ -1386,13 +1385,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, /* Check if we should syncronously wait for writeback */ if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { - /* - * The attempt at page out may have made some - * of the pages active, mark them inactive again. - */ - nr_active = clear_active_flags(&page_list, NULL); - count_vm_events(PGDEACTIVATE, nr_active); - set_lumpy_reclaim_mode(priority, sc, true); nr_reclaimed += shrink_page_list(&page_list, sc); } -- cgit v1.2.2 From 08fc468f4eaf6683bae5bdb94743a09d8630cb80 Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Tue, 26 Oct 2010 14:21:44 -0700 Subject: vmscan: isolate_lru_pages(): stop neighbour search if neighbour cannot be isolated isolate_lru_pages() does not just isolate LRU tail pages, but also isolates neighbour pages of the eviction page. The neighbour search does not stop even if neighbours cannot be isolated which is excessive as the lumpy reclaim will no longer result in a successful higher order allocation. This patch stops the PFN neighbour pages if an isolation fails and moves on to the next block. Signed-off-by: KOSAKI Motohiro Signed-off-by: Mel Gorman Reviewed-by: Wu Fengguang Reviewed-by: Minchan Kim Reviewed-by: KAMEZAWA Hiroyuki Cc: Johannes Weiner Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index cec8081bbd95..130ad0239f52 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1051,7 +1051,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, /* Check that we have not crossed a zone boundary. */ if (unlikely(page_zone_id(cursor_page) != zone_id)) - continue; + break; /* * If we don't have enough swap space, reclaiming of @@ -1059,8 +1059,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, * pointless. */ if (nr_swap_pages <= 0 && PageAnon(cursor_page) && - !PageSwapCache(cursor_page)) - continue; + !PageSwapCache(cursor_page)) + break; if (__isolate_lru_page(cursor_page, mode, file) == 0) { list_move(&cursor_page->lru, dst); @@ -1071,11 +1071,16 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, nr_lumpy_dirty++; scan++; } else { - if (mode == ISOLATE_BOTH && - page_count(cursor_page)) - nr_lumpy_failed++; + /* the page is freed already. */ + if (!page_count(cursor_page)) + continue; + break; } } + + /* If we break out of the loop above, lumpy reclaim failed */ + if (pfn < end_pfn) + nr_lumpy_failed++; } *scanned = scan; -- cgit v1.2.2 From 0e093d99763eb4cea09f8ca4f1d01f34e121d10b Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 26 Oct 2010 14:21:45 -0700 Subject: writeback: do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encountered in the current zone If congestion_wait() is called with no BDI congested, the caller will sleep for the full timeout and this may be an unnecessary sleep. This patch adds a wait_iff_congested() that checks congestion and only sleeps if a BDI is congested else, it calls cond_resched() to ensure the caller is not hogging the CPU longer than its quota but otherwise will not sleep. This is aimed at reducing some of the major desktop stalls reported during IO. For example, while kswapd is operating, it calls congestion_wait() but it could just have been reclaiming clean page cache pages with no congestion. Without this patch, it would sleep for a full timeout but after this patch, it'll just call schedule() if it has been on the CPU too long. Similar logic applies to direct reclaimers that are not making enough progress. Signed-off-by: Mel Gorman Cc: Johannes Weiner Cc: Minchan Kim Cc: Wu Fengguang Cc: KAMEZAWA Hiroyuki Cc: KOSAKI Motohiro Cc: Rik van Riel Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 42 +++++++++++++++++++++++++++++++++++------- 1 file changed, 35 insertions(+), 7 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 130ad0239f52..30fd658bb289 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -401,10 +401,8 @@ static pageout_t pageout(struct page *page, struct address_space *mapping, } if (mapping->a_ops->writepage == NULL) return PAGE_ACTIVATE; - if (!may_write_to_queue(mapping->backing_dev_info, sc)) { - disable_lumpy_reclaim_mode(sc); + if (!may_write_to_queue(mapping->backing_dev_info, sc)) return PAGE_KEEP; - } if (clear_page_dirty_for_io(page)) { int res; @@ -681,11 +679,14 @@ static noinline_for_stack void free_page_list(struct list_head *free_pages) * shrink_page_list() returns the number of reclaimed pages */ static unsigned long shrink_page_list(struct list_head *page_list, + struct zone *zone, struct scan_control *sc) { LIST_HEAD(ret_pages); LIST_HEAD(free_pages); int pgactivate = 0; + unsigned long nr_dirty = 0; + unsigned long nr_congested = 0; unsigned long nr_reclaimed = 0; cond_resched(); @@ -705,6 +706,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, goto keep; VM_BUG_ON(PageActive(page)); + VM_BUG_ON(page_zone(page) != zone); sc->nr_scanned++; @@ -782,6 +784,8 @@ static unsigned long shrink_page_list(struct list_head *page_list, } if (PageDirty(page)) { + nr_dirty++; + if (references == PAGEREF_RECLAIM_CLEAN) goto keep_locked; if (!may_enter_fs) @@ -792,6 +796,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, /* Page is dirty, try to write it out here */ switch (pageout(page, mapping, sc)) { case PAGE_KEEP: + nr_congested++; goto keep_locked; case PAGE_ACTIVATE: goto activate_locked; @@ -902,6 +907,15 @@ keep_lumpy: VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); } + /* + * Tag a zone as congested if all the dirty pages encountered were + * backed by a congested BDI. In this case, reclaimers should just + * back off and wait for congestion to clear because further reclaim + * will encounter the same problem + */ + if (nr_dirty == nr_congested) + zone_set_flag(zone, ZONE_CONGESTED); + free_page_list(&free_pages); list_splice(&ret_pages, page_list); @@ -1386,12 +1400,12 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, spin_unlock_irq(&zone->lru_lock); - nr_reclaimed = shrink_page_list(&page_list, sc); + nr_reclaimed = shrink_page_list(&page_list, zone, sc); /* Check if we should syncronously wait for writeback */ if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { set_lumpy_reclaim_mode(priority, sc, true); - nr_reclaimed += shrink_page_list(&page_list, sc); + nr_reclaimed += shrink_page_list(&page_list, zone, sc); } local_irq_disable(); @@ -1982,8 +1996,13 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, /* Take a nap, wait for some writeback to complete */ if (!sc->hibernation_mode && sc->nr_scanned && - priority < DEF_PRIORITY - 2) - congestion_wait(BLK_RW_ASYNC, HZ/10); + priority < DEF_PRIORITY - 2) { + struct zone *preferred_zone; + + first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), + NULL, &preferred_zone); + wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); + } } out: @@ -2282,6 +2301,15 @@ loop_again: if (!zone_watermark_ok(zone, order, min_wmark_pages(zone), end_zone, 0)) has_under_min_watermark_zone = 1; + } else { + /* + * If a zone reaches its high watermark, + * consider it to be no longer congested. It's + * possible there are dirty pages backed by + * congested BDIs but as pressure is relieved, + * spectulatively avoid congestion waits + */ + zone_clear_flag(zone, ZONE_CONGESTED); } } -- cgit v1.2.2 From 2e30244a7cc1ff09013a1238d415b4076406388e Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Tue, 26 Oct 2010 14:21:46 -0700 Subject: vmscan,tmpfs: treat used once pages on tmpfs as used once When a page has PG_referenced, shrink_page_list() discards it only if it is not dirty. This rule works fine if the backing filesystem is a regular one. PG_dirty is a good signal that the page was used recently because the flusher threads clean pages periodically. In addition, page writeback is costlier than simple page discard. However, when a page is on tmpfs this heuristic doesn't work because flusher threads don't write back tmpfs pages. Consequently tmpfs pages always rotate around the lru twice at least and adds unnecessary lru churn. Simple tmpfs streaming io shouldn't cause large anonymous page swap-out. Remove this unncessary reclaim bonus of tmpfs pages. Signed-off-by: KOSAKI Motohiro Cc: Hugh Dickins Reviewed-by: Johannes Weiner Reviewed-by: Rik van Riel Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 30fd658bb289..b8a6fdc21312 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -651,7 +651,7 @@ static enum page_references page_check_references(struct page *page, } /* Reclaim if clean, defer dirty pages to writeback */ - if (referenced_page) + if (referenced_page && !PageSwapBacked(page)) return PAGEREF_RECLAIM_CLEAN; return PAGEREF_RECLAIM; -- cgit v1.2.2 From 1dce071e18b7264457d17c0dec4c7e430bfaee7d Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Thu, 11 Nov 2010 14:05:17 -0800 Subject: vmscan: avoid setting zone congested if no page dirty nr_dirty and nr_congested are increased only when the page is dirty. So if all pages are clean, both them will be zero. In this case, we should not mark the zone congested. Signed-off-by: Shaohua Li Reviewed-by: Johannes Weiner Reviewed-by: Minchan Kim Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index b8a6fdc21312..d31d7ce52c0e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -913,7 +913,7 @@ keep_lumpy: * back off and wait for congestion to clear because further reclaim * will encounter the same problem */ - if (nr_dirty == nr_congested) + if (nr_dirty == nr_congested && nr_dirty != 0) zone_set_flag(zone, ZONE_CONGESTED); free_page_list(&free_pages); -- cgit v1.2.2