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| * sched: Do less agressive buddy clearingPeter Zijlstra2009-10-14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Yanmin reported a hackbench regression due to: > commit de69a80be32445b0a71e8e3b757e584d7beb90f7 > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > Date: Thu Sep 17 09:01:20 2009 +0200 > > sched: Stop buddies from hogging the system I really liked de69a80b, and it affecting hackbench shows I wasn't crazy ;-) So hackbench is a multi-cast, with one sender spraying multiple receivers, who in their turn don't spray back. This would be exactly the scenario that patch 'cures'. Previously we would not clear the last buddy after running the next task, allowing the sender to get back to work sooner than it otherwise ought to have been, increasing latencies for other tasks. Now, since those receivers don't poke back, they don't enforce the buddy relation, which means there's nothing to re-elect the sender. Cure this by less agressively clearing the buddy stats. Only clear buddies when they were not chosen. It should still avoid a buddy sticking around long after its served its time. Reported-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> CC: Mike Galbraith <efault@gmx.de> LKML-Reference: <1255084986.8802.46.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: Optimize branch hint in pick_next_task_fair()Tim Blechmann2009-11-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Branch hint profiling on my nehalem machine showed 90% incorrect branch hints: 15728471 158903754 90 pick_next_task_fair sched_fair.c 1555 Signed-off-by: Tim Blechmann <tim@klingt.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <4B0BBBB1.2050100@klingt.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: More generic WAKE_AFFINE vs select_idle_sibling()Peter Zijlstra2009-11-13
| | | | | | | | | | | | | | | | | | | | | | Instead of only considering SD_WAKE_AFFINE | SD_PREFER_SIBLING domains also allow all SD_PREFER_SIBLING domains below a SD_WAKE_AFFINE domain to change the affinity target. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <20091112145610.909723612@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: Cleanup select_task_rq_fair()Peter Zijlstra2009-11-13
| | | | | | | | | | | | | | | | | | | | Clean up the new affine to idle sibling bits while trying to grok them. Should not have any function differences. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <20091112145610.832503781@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: Fix affinity logic in select_task_rq_fair()Mike Galbraith2009-11-05
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Ingo Molnar reported: [ 26.804000] BUG: using smp_processor_id() in preemptible [00000000] code: events/1/10 [ 26.808000] caller is vmstat_update+0x26/0x70 [ 26.812000] Pid: 10, comm: events/1 Not tainted 2.6.32-rc5 #6887 [ 26.816000] Call Trace: [ 26.820000] [<c1924a24>] ? printk+0x28/0x3c [ 26.824000] [<c13258a0>] debug_smp_processor_id+0xf0/0x110 [ 26.824000] mount used greatest stack depth: 1464 bytes left [ 26.828000] [<c111d086>] vmstat_update+0x26/0x70 [ 26.832000] [<c1086418>] worker_thread+0x188/0x310 [ 26.836000] [<c10863b7>] ? worker_thread+0x127/0x310 [ 26.840000] [<c108d310>] ? autoremove_wake_function+0x0/0x60 [ 26.844000] [<c1086290>] ? worker_thread+0x0/0x310 [ 26.848000] [<c108cf0c>] kthread+0x7c/0x90 [ 26.852000] [<c108ce90>] ? kthread+0x0/0x90 [ 26.856000] [<c100c0a7>] kernel_thread_helper+0x7/0x10 [ 26.860000] BUG: using smp_processor_id() in preemptible [00000000] code: events/1/10 [ 26.864000] caller is vmstat_update+0x3c/0x70 Because this commit: a1f84a3: sched: Check for an idle shared cache in select_task_rq_fair() broke ->cpus_allowed. Signed-off-by: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: arjan@infradead.org Cc: <stable@kernel.org> LKML-Reference: <1257415066.12867.1.camel@marge.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: Check for an idle shared cache in select_task_rq_fair()Mike Galbraith2009-11-04
|/ | | | | | | | | | | | | | | | When waking affine, check for an idle shared cache, and if found, wake to that CPU/sibling instead of the waker's CPU. This improves pgsql+oltp ramp up by roughly 8%. Possibly more for other loads, depending on overlap. The trade-off is a roughly 1% peak downturn if tasks are truly synchronous. Signed-off-by: Mike Galbraith <efault@gmx.de> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: <stable@kernel.org> LKML-Reference: <1256654138.17752.7.camel@marge.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sysctl: remove "struct file *" argument of ->proc_handlerAlexey Dobriyan2009-09-24
| | | | | | | | | | | | | | | | | | | | | It's unused. It isn't needed -- read or write flag is already passed and sysctl shouldn't care about the rest. It _was_ used in two places at arch/frv for some reason. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: David Howells <dhowells@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: "David S. Miller" <davem@davemloft.net> Cc: James Morris <jmorris@namei.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge branch 'sched-fixes-for-linus' of ↵Linus Torvalds2009-09-21
|\ | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: sched: Simplify sys_sched_rr_get_interval() system call sched: Fix potential NULL derference of doms_cur sched: Fix raciness in runqueue_is_locked() sched: Re-add lost cpu_allowed check to sched_fair.c::select_task_rq_fair() sched: Remove unneeded indentation in sched_fair.c::place_entity()
| * sched: Simplify sys_sched_rr_get_interval() system callPeter Williams2009-09-21
| | | | | | | | | | | | | | | | | | | | | | | | By removing the need for it to know details of scheduling classes. This allows PlugSched to define orthogonal scheduling classes. Signed-off-by: Peter Williams <pwil3058@bigpond.net.au> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <06d1b89ee15a0eef82d7.1253496713@mudlark.pw.nest> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Re-add lost cpu_allowed check to sched_fair.c::select_task_rq_fair()Mike Galbraith2009-09-19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | While doing some testing, I pinned mplayer, only to find it following X around like a puppy. Looking at commit c88d591, I found a cpu_allowed check that went AWOL. I plugged it back in where it looks like it needs to go, and now when I say "sit, stay!", mplayer obeys again. 'c88d591 sched: Merge select_task_rq_fair() and sched_balance_self()' accidentally dropped the check, causing wake_affine() to pull pinned tasks - put it back. [ v2: use a cheaper version from Peter ] Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Remove unneeded indentation in sched_fair.c::place_entity()Mike Galbraith2009-09-18
| | | | | | | | | | | | | | Signed-off-by: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1253258365.22787.33.camel@marge.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | Merge branch 'linus' into perfcounters/coreIngo Molnar2009-09-19
|\| | | | | | | | | | | Merge reason: Bring in tracing changes we depend on. Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Fix SD_POWERSAVING_BALANCE|SD_PREFER_LOCAL vs SD_WAKE_AFFINEPeter Zijlstra2009-09-17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The SD_POWERSAVING_BALANCE|SD_PREFER_LOCAL code can break out of the domain iteration early, making us miss the SD_WAKE_AFFINE bits. Fix this by continuing iteration until there is no need for a larger domain. This also cleans up the cgroup stuff a bit, but not having two update_shares() invocations. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Stop buddies from hogging the systemPeter Zijlstra2009-09-17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Clear buddies more agressively. The (theoretical, haven't actually observed any of this) problem is that when we do not select either buddy in pick_next_entity() because they are too far ahead of the left-most task, we do not clear the buddies. This means that as soon as we service the left-most task, these same buddies will be tried again on the next schedule. Now if the left-most task was a pure hog, it wouldn't have done any wakeups and it wouldn't have set buddies of its own. That leads to the old buddies dominating, which would lead to bad latencies. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Add new wakeup preemption mode: WAKEUP_RUNNINGPeter Zijlstra2009-09-17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Create a new wakeup preemption mode, preempt towards tasks that run shorter on avg. It sets next buddy to be sure we actually run the task we preempted for. Test results: root@twins:~# while :; do :; done & [1] 6537 root@twins:~# while :; do :; done & [2] 6538 root@twins:~# while :; do :; done & [3] 6539 root@twins:~# while :; do :; done & [4] 6540 root@twins:/home/peter# ./latt -c4 sleep 4 Entries: 48 (clients=4) Averages: ------------------------------ Max 4750 usec Avg 497 usec Stdev 737 usec root@twins:/home/peter# echo WAKEUP_RUNNING > /debug/sched_features root@twins:/home/peter# ./latt -c4 sleep 4 Entries: 48 (clients=4) Averages: ------------------------------ Max 14 usec Avg 5 usec Stdev 3 usec Disabled by default - needs more testing. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> LKML-Reference: <new-submission>
| * sched: Rename flags to wake_flagsPeter Zijlstra2009-09-16
| | | | | | | | | | | | | | | | For consistencies sake, rename the argument (again). Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Clean up the load_idx selection in select_task_rq_fairPeter Zijlstra2009-09-16
| | | | | | | | | | | | | | | | Clean up the code a little. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Optimize cgroup vs wakeup a bitPeter Zijlstra2009-09-16
| | | | | | | | | | | | | | | | | | | | | | | | We don't need to call update_shares() for each domain we iterate, just got the largets one. However, we should call it before wake_affine() as well, so that that can use up-to-date values too. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Implement a gentler fair-sleepers featureIngo Molnar2009-09-16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add back FAIR_SLEEPERS and GENTLE_FAIR_SLEEPERS. FAIR_SLEEPERS is the old logic: credit sleepers with their sleep time. GENTLE_FAIR_SLEEPERS dampens this a bit: 50% of their sleep time gets credited. The hope here is to still give the benefits of fair-sleepers logic (quick wakeups, etc.) while not allow them to have 100% of their sleep time as if they were running. Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Add SD_PREFER_LOCALPeter Zijlstra2009-09-16
| | | | | | | | | | | | | | | | | | | | | | | | And turn it on for NUMA and MC domains. This improves locality in balancing decisions by keeping up to capacity amount of tasks local before looking for idle CPUs. (and twice the capacity if SD_POWERSAVINGS_BALANCE is set.) Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Add a few SYNC hint knobs to play withPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently we use overlap to weaken the SYNC hint, but allow it to set the hint as well. echo NO_SYNC_WAKEUP > /debug/sched_features echo SYNC_MORE > /debug/sched_features preserves pipe-test behaviour without using the WF_SYNC hint. Worth playing with on more workloads... Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Add WF_FORKPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | | | | | | | Avoid the cache buddies from biasing the time distribution away from fork()ers. Normally the next buddy will be the preferred scheduling target, but this makes fork()s prefer to run the new child, whereas we prefer to run the parent, since that will generate more work. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Rename sync argumentsPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | | | In order to extend the functions to have more than 1 flag (sync), rename the argument to flags, and explicitly define a WF_ space for individual flags. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Rename select_task_rq() argumentPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | In order to be able to rename the sync argument, we need to rename the current flag argument. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Tweak wake_idxPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | | | When merging select_task_rq_fair() and sched_balance_self() we lost the use of wake_idx, restore that and set them to 0 to make wake balancing more aggressive. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Fix task affinity for select_task_rq_fairPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | While merging select_task_rq_fair() and sched_balance_self() I made a mistake that leads to testing the wrong task affinty. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: for_each_domain() vs RCUPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | | | | | | | for_each_domain() uses RCU to serialize the sched_domains, except it doesn't actually use rcu_read_lock() and instead relies on disabling preemption -> FAIL. XXX: audit other sched_domain code. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Weaken SD_POWERSAVINGS_BALANCEPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | | | | | | | One of the problems of power-saving balancing is that under certain scenarios it is too slow and allows tons of real work to pile up. Avoid this by ignoring the powersave stuff when there's real work to be done. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Merge select_task_rq_fair() and sched_balance_self()Peter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The problem with wake_idle() is that is doesn't respect things like cpu_power, which means it doesn't deal well with SMT nor the recent RT interaction. To cure this, it needs to do what sched_balance_self() does, which leads to the possibility of merging select_task_rq_fair() and sched_balance_self(). Modify sched_balance_self() to: - update_shares() when walking up the domain tree, (it only called it for the top domain, but it should have done this anyway), which allows us to remove this ugly bit from try_to_wake_up(). - do wake_affine() on the smallest domain that contains both this (the waking) and the prev (the wakee) cpu for WAKE invocations. Then use the top-down balance steps it had to replace wake_idle(). This leads to the dissapearance of SD_WAKE_BALANCE and SD_WAKE_IDLE_FAR, with SD_WAKE_IDLE replaced with SD_BALANCE_WAKE. SD_WAKE_AFFINE needs SD_BALANCE_WAKE to be effective. Touch all topology bits to replace the old with new SD flags -- platforms might need re-tuning, enabling SD_BALANCE_WAKE conditionally on a NUMA distance seems like a good additional feature, magny-core and small nehalem systems would want this enabled, systems with slow interconnects would not. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Hook sched_balance_self() into sched_class::select_task_rq()Peter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | Rather ugly patch to fully place the sched_balance_self() code inside the fair class. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Move sched_balance_self() into sched_fair.cPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | | | | | Move the sched_balance_self() code into sched_fair.c This facilitates the merger of sched_balance_self() and sched_fair::select_task_rq(). Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Complete buddy switchesMike Galbraith2009-09-15
| | | | | | | | | | | | | | | | | | Add a NEXT_BUDDY feature flag to aid in debugging. Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * sched: Split WAKEUP_OVERLAPPeter Zijlstra2009-09-15
| | | | | | | | | | | | | | | | | | It consists of two conditions, split them out in separate toggles so we can test them independently. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | perf_counter, sched: Add sched_stat_runtime tracepointIngo Molnar2009-09-13
|/ | | | | | | | | | | | | This allows more precise tracking of how the scheduler accounts (and acts upon) a task having spent N nanoseconds of CPU time. Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Fix sched::sched_stat_wait tracepoint fieldIngo Molnar2009-09-10
| | | | | | | | | | | | | | | | | | | This weird perf trace output: cc1-9943 [001] 2802.059479616: sched_stat_wait: task: as:9944 wait: 2801938766276 [ns] Is caused by setting one component field of the delta to zero a bit too early. Move it to later. ( Note, this does not affect the NEW_FAIR_SLEEPERS interactivity bug, it's just a reporting bug in essence. ) Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Nikos Chantziaras <realnc@arcor.de> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <4AA93D34.8040500@arcor.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Re-tune the scheduler latency defaults to decrease worst-case latenciesMike Galbraith2009-09-09
| | | | | | | | | | | | | | | Reduce the latency target from 20 msecs to 5 msecs. Why? Larger latencies increase spread, which is good for scaling, but bad for worst case latency. We still have the ilog(nr_cpus) rule to scale up on bigger server boxes. Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1252486344.28645.18.camel@marge.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Turn off child_runs_firstMike Galbraith2009-09-09
| | | | | | | | | | | | | | | | | | | | | | | Set child_runs_first default to off. It hurts 'optimal' make -j<NR_CPUS> workloads as make jobs get preempted by child tasks, reducing parallelism. Note, this patch might make existing races in user applications more prominent than before - so breakages might be bisected to this commit. Child-runs-first is broken on SMP to begin with, and we already had it off briefly in v2.6.23 so most of the offenders ought to be fixed. Would be nice not to revert this commit but fix those apps finally ... Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1252486344.28645.18.camel@marge.simson.net> [ made the sysctl independent of CONFIG_SCHED_DEBUG, in case people want to work around broken apps. ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Ensure that a child can't gain time over it's parent after fork()Mike Galbraith2009-09-08
| | | | | | | | | | | | | | | | | | | | | | | | | | | | A fork/exec load is usually "pass the baton", so the child should never be placed behind the parent. With START_DEBIT we make room for the new task, but with child_runs_first, that room comes out of the _parent's_ hide. There's nothing to say that the parent wasn't ahead of min_vruntime at fork() time, which means that the "baton carrier", who is essentially the parent in drag, can gain time and increase scheduling latencies for waiters. With NEW_FAIR_SLEEPERS + START_DEBIT + child_runs_first enabled, we essentially pass the sleeper fairness off to the child, which is fine, but if we don't base placement on the parent's updated vruntime, we can end up compounding latency woes if the child itself then does fork/exec. The debit incurred at fork doesn't hurt the parent who is then going to sleep and maybe exit, but the child who acquires the error harms all comers. This improves latencies of make -j<n> kernel build workloads. Reported-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Deal with low-load in wake_affine()Peter Zijlstra2009-09-07
| | | | | | | | | | | | | | wake_affine() would always fail under low-load situations where both prev and this were idle, because adding a single task will always be a significant imbalance, even if there's nothing around that could balance it. Deal with this by allowing imbalance when there's nothing you can do about it. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Remove short cut from select_task_rq_fair()Peter Zijlstra2009-09-07
| | | | | | | | | | | | | select_task_rq_fair() incorrectly skips the wake_affine() logic, remove this. When prev_cpu == this_cpu, the code jumps straight to the wake_idle() logic, this doesn't give the wake_affine() logic the chance to pin the task to this cpu. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Add wait, sleep and iowait accounting tracepointsPeter Zijlstra2009-09-02
| | | | | | | | | | | | | | | | Add 3 schedstat tracepoints to help account for wait-time, sleep-time and iowait-time. They can also be used as a perf-counter source to profile tasks on these clocks. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Arjan van de Ven <arjan@linux.intel.com> LKML-Reference: <new-submission> [ build fix for the !CONFIG_SCHEDSTATS case ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Provide iowait countersArjan van de Ven2009-09-02
| | | | | | | | | | | | | | | | | | For counting how long an application has been waiting for (disk) IO, there currently is only the HZ sample driven information available, while for all other counters in this class, a high resolution version is available via CONFIG_SCHEDSTATS. In order to make an improved bootchart tool possible, we also need a higher resolution version of the iowait time. This patch below adds this scheduler statistic to the kernel. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <4A64B813.1080506@linux.intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Add debug check to task_of()Peter Zijlstra2009-08-02
| | | | | | | | | | | | | A frequent mistake appears to be to call task_of() on a scheduler entity that is not actually a task, which can result in a wild pointer. Add a check to catch these mistakes. Suggested-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Fully integrate cpus_active_map and root-domain codeGregory Haskins2009-08-02
| | | | | | | | | | | | | | | | | | | | | Reflect "active" cpus in the rq->rd->online field, instead of the online_map. The motivation is that things that use the root-domain code (such as cpupri) only care about cpus classified as "active" anyway. By synchronizing the root-domain state with the active map, we allow several optimizations. For instance, we can remove an extra cpumask_and from the scheduler hotpath by utilizing rq->rd->online (since it is now a cached version of cpu_active_map & rq->rd->span). Signed-off-by: Gregory Haskins <ghaskins@novell.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Max Krasnyansky <maxk@qualcomm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20090730145723.25226.24493.stgit@dev.haskins.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Fix latencytop and sleep profiling vs group schedulingPeter Zijlstra2009-08-02
| | | | | | | | | The latencytop and sleep accounting code assumes that any scheduler entity represents a task, this is not so. Cc: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Account for vruntime wrappingFabio Checconi2009-07-18
| | | | | | | | | | | I spotted two sites that didn't take vruntime wrap-around into account. Fix these by creating a comparison helper that does do so. Signed-off-by: Fabio Checconi <fabio@gandalf.sssup.it> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Fix bug in SCHED_IDLE interaction with group schedulingPaul Turner2009-07-11
| | | | | | | | | | | | | | | One of the isolation modifications for SCHED_IDLE is the unitization of sleeper credit. However the check for this assumes that the sched_entity we're placing always belongs to a task. This is potentially not true with group scheduling and leaves us rummaging randomly when we try to pull the policy. Signed-off-by: Paul Turner <pjt@google.com> Cc: peterz@infradead.org LKML-Reference: <alpine.DEB.1.00.0907101649570.29914@kitami.corp.google.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: Fix out of scope variable access in sched_slice()Christian Engelmayer2009-06-17
| | | | | | | | | | | | Access to local variable lw is aliased by usage of pointer load. Access to pointer load in calc_delta_mine() happens when lw is already out of scope. [ Reported by static code analysis. ] Signed-off-by: Christian Engelmayer <christian.engelmayer@frequentis.com> LKML-Reference: <20090616103512.0c846e51@frequentis.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: remove redundant hierarchy walk in check_preempt_wakeupPaul Turner2009-04-09
| | | | | | | | | | | | | | | Impact: micro-optimization Under group scheduling we traverse up until we are at common siblings to make the wakeup comparison on. At this point however, they should have the same parent so continuing to check up the tree is redundant. Signed-off-by: Paul Turner <pjt@google.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <alpine.DEB.1.00.0904081520320.30317@kitami.corp.google.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Merge branch 'sched/urgent'; commit 'v2.6.29-rc5' into sched/coreIngo Molnar2009-02-15
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