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* ARM: Kirkwood: Recognize A1 revision of 6282 chipMartin Michlmayr2011-12-13
* ARM: orion: Consolidate setup of the crypto engine.Andrew Lunn2011-05-16
* ARM: orion: Consolidate SATA platform setup.Andrew Lunn2011-05-16
* ARM: orion: Consolidate USB platform setup code.Andrew Lunn2011-05-16
* ARM: orion: Consolidate the XOR platform setup code.Andrew Lunn2011-05-16
* ARM: orion: Consolidate the platform data setup for the watchdog.Andrew Lunn2011-05-16
* ARM: orion: Consolidate SPI initialization.Andrew Lunn2011-05-16
* ARM: orion: Consolidate I2C initialization.Andrew Lunn2011-05-16
* ARM: orion: Consolidate ethernet platform dataAndrew Lunn2011-05-16
* ARM: kirkwood: Add support for RTC interrupts which allows RTC alarms.Andrew Lunn2011-05-16
* ARM: orion: Consolidate the creation of the RTC platform data.Andrew Lunn2011-05-16
* ARM: orion: Consolidate the creation of the uart platform data.Andrew Lunn2011-05-16
* ARM: orion: Rename some constants to macros to make code more identicalAndrew Lunn2011-05-16
* ARM: Remove dependency of plat-orion time code on mach directory includes.Lennert Buytenhek2011-03-03
* [ARM] Kirkwood: make kirkwood_find_tclk() staticNicolas Pitre2011-03-03
* [ARM] Kirkwood: enable PCIe for kexecEric Cooper2011-03-03
* Merge git://git.kernel.org/pub/scm/linux/kernel/git/nico/orionRussell King2010-11-07
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| * [ARM] Kirkwood: enhance TCLK detectionSimon Guinot2010-10-21
* | ASoC: OpenRD Client : Fix naming breakage due to multicomponent supportArnaud Patard (Rtp)2010-08-31
* | Merge branch 'for-2.6.36' into for-2.6.37Mark Brown2010-08-16
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| * Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiw...Linus Torvalds2010-08-07
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| * | [ARM] Kirkwood: add support for PCIe1Saeed Bishara2010-07-16
| * | [ARM] Kirkwood: Add support for 88f6282Saeed Bishara2010-07-16
| * | [ARM] Kirkwood: add support for rev A1 of the 88f6192 and 88f6180 chips.Saeed Bishara2010-07-16
* | | ASoC: multi-component - ASoC Multi-Component SupportLiam Girdwood2010-08-12
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* | orion/kirkwood: add audio functions.apatard@mandriva.com2010-05-31
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* mtd: kirkwood: allow machines to register RnB callbackBen Dooks2010-05-13
* mach-kirkwood/common.c: remove unnecessary (void *) castsH Hartley Sweeten2010-02-04
* [ARM] Kirkwood: disable propagation of mbus error to the CPU local busLennert Buytenhek2009-11-13
* [ARM] kirkwood: fix section mismatchLi Jie2009-11-05
* [ARM] Kirkwood: Add support for 6281-A1Siddarth Gore2009-08-10
* [ARM] Kirkwood: platform device registration for the crypto engineNicolas Pitre2009-06-08
* [ARM] Orion/Kirkwood: rename orion5x_wdt to orion_wdtNicolas Pitre2009-06-08
* [ARM] Kirkwood: Add the watchdog timer as a platform device.Thomas Reitmayr2009-06-08
* [ARM] Kirkwood: clock gating for unused peripheralsRabeeh Khoury2009-06-08
* [ARM] Kirkwood: rationalize NAND setup a bitNicolas Pitre2009-06-08
* [ARM] add coherent DMA mask for mv643xx_ethNicolas Pitre2009-05-22
* [ARM] Orion: Remove explicit name for platform device resourcesMartin Michlmayr2009-05-21
* [ARM] 5460/1: Orion: reduce namespace pollutionNicolas Pitre2009-04-23
* dma-mapping: replace all DMA_32BIT_MASK macro with DMA_BIT_MASK(32)Yang Hongyang2009-04-07
* dma-mapping: replace all DMA_64BIT_MASK macro with DMA_BIT_MASK(64)Yang Hongyang2009-04-07
* Merge branch 'origin' into develRussell King2009-03-28
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| * dsa: add switch chip cascading supportLennert Buytenhek2009-03-21
* | [ARM] Kirkwood: Hook up I2CMartin Michlmayr2009-03-23
* | [ARM] Kirkwood: register internal devices in a common placeNicolas Pitre2009-02-26
* | [ARM] Kirkwood: SDIO driver registration for DB6281 and RD6281Nicolas Pitre2009-02-26
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* [ARM] 5357/1: Kirkwood: add missing ge01 tclk initializationNicolas Pitre2009-01-08
* [ARM] Kirkwood: allow instantiating the second ethernet portRonen Shitrit2008-12-11
* [ARM] Orion: add the option to support different ehci phy initializationRonen Shitrit2008-12-04
* [ARM] Orion: instantiate the dsa switch driverLennert Buytenhek2008-10-19
generated by cgit v1.2.2 (git 2.25.0) at 2024-12-26 00:58:01 -0500
ass="hl com"> * - Monitor latencies in a defined window of time. * - If the minimum latency in the above window exceeds some target, increment * scaling step and scale down queue depth by a factor of 2x. The monitoring * window is then shrunk to 100 / sqrt(scaling step + 1). * - For any window where we don't have solid data on what the latencies * look like, retain status quo. * - If latencies look good, decrement scaling step. * - If we're only doing writes, allow the scaling step to go negative. This * will temporarily boost write performance, snapping back to a stable * scaling step of 0 if reads show up or the heavy writers finish. Unlike * positive scaling steps where we shrink the monitoring window, a negative * scaling step retains the default step==0 window size. * * Copyright (C) 2016 Jens Axboe * */ #include <linux/kernel.h> #include <linux/blk_types.h> #include <linux/slab.h> #include <linux/backing-dev.h> #include <linux/swap.h> #include "blk-wbt.h" #define CREATE_TRACE_POINTS #include <trace/events/wbt.h> enum { /* * Default setting, we'll scale up (to 75% of QD max) or down (min 1) * from here depending on device stats */ RWB_DEF_DEPTH = 16, /* * 100msec window */ RWB_WINDOW_NSEC = 100 * 1000 * 1000ULL, /* * Disregard stats, if we don't meet this minimum */ RWB_MIN_WRITE_SAMPLES = 3, /* * If we have this number of consecutive windows with not enough * information to scale up or down, scale up. */ RWB_UNKNOWN_BUMP = 5, }; static inline bool rwb_enabled(struct rq_wb *rwb) { return rwb && rwb->wb_normal != 0; } /* * Increment 'v', if 'v' is below 'below'. Returns true if we succeeded, * false if 'v' + 1 would be bigger than 'below'. */ static bool atomic_inc_below(atomic_t *v, int below) { int cur = atomic_read(v); for (;;) { int old; if (cur >= below) return false; old = atomic_cmpxchg(v, cur, cur + 1); if (old == cur) break; cur = old; } return true; } static void wb_timestamp(struct rq_wb *rwb, unsigned long *var) { if (rwb_enabled(rwb)) { const unsigned long cur = jiffies; if (cur != *var) *var = cur; } } /* * If a task was rate throttled in balance_dirty_pages() within the last * second or so, use that to indicate a higher cleaning rate. */ static bool wb_recent_wait(struct rq_wb *rwb) { struct bdi_writeback *wb = &rwb->queue->backing_dev_info.wb; return time_before(jiffies, wb->dirty_sleep + HZ); } static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb, bool is_kswapd) { return &rwb->rq_wait[is_kswapd]; } static void rwb_wake_all(struct rq_wb *rwb) { int i; for (i = 0; i < WBT_NUM_RWQ; i++) { struct rq_wait *rqw = &rwb->rq_wait[i]; if (waitqueue_active(&rqw->wait)) wake_up_all(&rqw->wait); } } void __wbt_done(struct rq_wb *rwb, enum wbt_flags wb_acct) { struct rq_wait *rqw; int inflight, limit; if (!(wb_acct & WBT_TRACKED)) return; rqw = get_rq_wait(rwb, wb_acct & WBT_KSWAPD); inflight = atomic_dec_return(&rqw->inflight); /* * wbt got disabled with IO in flight. Wake up any potential * waiters, we don't have to do more than that. */ if (unlikely(!rwb_enabled(rwb))) { rwb_wake_all(rwb); return; } /* * If the device does write back caching, drop further down * before we wake people up. */ if (rwb->wc && !wb_recent_wait(rwb)) limit = 0; else limit = rwb->wb_normal; /* * Don't wake anyone up if we are above the normal limit. */ if (inflight && inflight >= limit) return; if (waitqueue_active(&rqw->wait)) { int diff = limit - inflight; if (!inflight || diff >= rwb->wb_background / 2) wake_up_all(&rqw->wait); } } /* * Called on completion of a request. Note that it's also called when * a request is merged, when the request gets freed. */ void wbt_done(struct rq_wb *rwb, struct blk_issue_stat *stat) { if (!rwb) return; if (!wbt_is_tracked(stat)) { if (rwb->sync_cookie == stat) { rwb->sync_issue = 0; rwb->sync_cookie = NULL; } if (wbt_is_read(stat)) wb_timestamp(rwb, &rwb->last_comp); wbt_clear_state(stat); } else { WARN_ON_ONCE(stat == rwb->sync_cookie); __wbt_done(rwb, wbt_stat_to_mask(stat)); wbt_clear_state(stat); } } /* * Return true, if we can't increase the depth further by scaling */ static bool calc_wb_limits(struct rq_wb *rwb) { unsigned int depth; bool ret = false; if (!rwb->min_lat_nsec) { rwb->wb_max = rwb->wb_normal = rwb->wb_background = 0; return false; } /* * For QD=1 devices, this is a special case. It's important for those * to have one request ready when one completes, so force a depth of * 2 for those devices. On the backend, it'll be a depth of 1 anyway, * since the device can't have more than that in flight. If we're * scaling down, then keep a setting of 1/1/1. */ if (rwb->queue_depth == 1) { if (rwb->scale_step > 0) rwb->wb_max = rwb->wb_normal = 1; else { rwb->wb_max = rwb->wb_normal = 2; ret = true; } rwb->wb_background = 1; } else { /* * scale_step == 0 is our default state. If we have suffered * latency spikes, step will be > 0, and we shrink the * allowed write depths. If step is < 0, we're only doing * writes, and we allow a temporarily higher depth to * increase performance. */ depth = min_t(unsigned int, RWB_DEF_DEPTH, rwb->queue_depth); if (rwb->scale_step > 0) depth = 1 + ((depth - 1) >> min(31, rwb->scale_step)); else if (rwb->scale_step < 0) { unsigned int maxd = 3 * rwb->queue_depth / 4; depth = 1 + ((depth - 1) << -rwb->scale_step); if (depth > maxd) { depth = maxd; ret = true; } } /* * Set our max/normal/bg queue depths based on how far * we have scaled down (->scale_step). */ rwb->wb_max = depth; rwb->wb_normal = (rwb->wb_max + 1) / 2; rwb->wb_background = (rwb->wb_max + 3) / 4; } return ret; } static bool inline stat_sample_valid(struct blk_rq_stat *stat) { /* * We need at least one read sample, and a minimum of * RWB_MIN_WRITE_SAMPLES. We require some write samples to know * that it's writes impacting us, and not just some sole read on * a device that is in a lower power state. */ return stat[0].nr_samples >= 1 && stat[1].nr_samples >= RWB_MIN_WRITE_SAMPLES; } static u64 rwb_sync_issue_lat(struct rq_wb *rwb) { u64 now, issue = ACCESS_ONCE(rwb->sync_issue); if (!issue || !rwb->sync_cookie) return 0; now = ktime_to_ns(ktime_get()); return now - issue; } enum { LAT_OK = 1, LAT_UNKNOWN, LAT_UNKNOWN_WRITES, LAT_EXCEEDED, }; static int __latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat) { struct backing_dev_info *bdi = &rwb->queue->backing_dev_info; u64 thislat; /* * If our stored sync issue exceeds the window size, or it * exceeds our min target AND we haven't logged any entries, * flag the latency as exceeded. wbt works off completion latencies, * but for a flooded device, a single sync IO can take a long time * to complete after being issued. If this time exceeds our * monitoring window AND we didn't see any other completions in that * window, then count that sync IO as a violation of the latency. */ thislat = rwb_sync_issue_lat(rwb); if (thislat > rwb->cur_win_nsec || (thislat > rwb->min_lat_nsec && !stat[0].nr_samples)) { trace_wbt_lat(bdi, thislat); return LAT_EXCEEDED; } /* * No read/write mix, if stat isn't valid */ if (!stat_sample_valid(stat)) { /* * If we had writes in this stat window and the window is * current, we're only doing writes. If a task recently * waited or still has writes in flights, consider us doing * just writes as well. */ if ((stat[1].nr_samples && blk_stat_is_current(stat)) || wb_recent_wait(rwb) || wbt_inflight(rwb)) return LAT_UNKNOWN_WRITES; return LAT_UNKNOWN; } /* * If the 'min' latency exceeds our target, step down. */ if (stat[0].min > rwb->min_lat_nsec) { trace_wbt_lat(bdi, stat[0].min); trace_wbt_stat(bdi, stat); return LAT_EXCEEDED; } if (rwb->scale_step) trace_wbt_stat(bdi, stat); return LAT_OK; } static int latency_exceeded(struct rq_wb *rwb) { struct blk_rq_stat stat[2]; blk_queue_stat_get(rwb->queue, stat); return __latency_exceeded(rwb, stat); } static void rwb_trace_step(struct rq_wb *rwb, const char *msg) { struct backing_dev_info *bdi = &rwb->queue->backing_dev_info; trace_wbt_step(bdi, msg, rwb->scale_step, rwb->cur_win_nsec, rwb->wb_background, rwb->wb_normal, rwb->wb_max); } static void scale_up(struct rq_wb *rwb) { /* * Hit max in previous round, stop here */ if (rwb->scaled_max) return; rwb->scale_step--; rwb->unknown_cnt = 0; blk_stat_clear(rwb->queue); rwb->scaled_max = calc_wb_limits(rwb); rwb_wake_all(rwb); rwb_trace_step(rwb, "step up"); } /* * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we * had a latency violation. */ static void scale_down(struct rq_wb *rwb, bool hard_throttle) { /* * Stop scaling down when we've hit the limit. This also prevents * ->scale_step from going to crazy values, if the device can't * keep up. */ if (rwb->wb_max == 1) return; if (rwb->scale_step < 0 && hard_throttle) rwb->scale_step = 0; else rwb->scale_step++; rwb->scaled_max = false; rwb->unknown_cnt = 0; blk_stat_clear(rwb->queue); calc_wb_limits(rwb); rwb_trace_step(rwb, "step down"); } static void rwb_arm_timer(struct rq_wb *rwb) { unsigned long expires; if (rwb->scale_step > 0) { /* * We should speed this up, using some variant of a fast * integer inverse square root calculation. Since we only do * this for every window expiration, it's not a huge deal, * though. */ rwb->cur_win_nsec = div_u64(rwb->win_nsec << 4, int_sqrt((rwb->scale_step + 1) << 8)); } else { /* * For step < 0, we don't want to increase/decrease the * window size. */ rwb->cur_win_nsec = rwb->win_nsec; } expires = jiffies + nsecs_to_jiffies(rwb->cur_win_nsec); mod_timer(&rwb->window_timer, expires); } static void wb_timer_fn(unsigned long data) { struct rq_wb *rwb = (struct rq_wb *) data; unsigned int inflight = wbt_inflight(rwb); int status; status = latency_exceeded(rwb); trace_wbt_timer(&rwb->queue->backing_dev_info, status, rwb->scale_step, inflight); /* * If we exceeded the latency target, step down. If we did not, * step one level up. If we don't know enough to say either exceeded * or ok, then don't do anything. */ switch (status) { case LAT_EXCEEDED: scale_down(rwb, true); break; case LAT_OK: scale_up(rwb); break; case LAT_UNKNOWN_WRITES: /* * We started a the center step, but don't have a valid * read/write sample, but we do have writes going on. * Allow step to go negative, to increase write perf. */ scale_up(rwb); break; case LAT_UNKNOWN: if (++rwb->unknown_cnt < RWB_UNKNOWN_BUMP) break; /* * We get here when previously scaled reduced depth, and we * currently don't have a valid read/write sample. For that * case, slowly return to center state (step == 0). */ if (rwb->scale_step > 0) scale_up(rwb); else if (rwb->scale_step < 0) scale_down(rwb, false); break; default: break; } /* * Re-arm timer, if we have IO in flight */ if (rwb->scale_step || inflight) rwb_arm_timer(rwb); } void wbt_update_limits(struct rq_wb *rwb) { rwb->scale_step = 0; rwb->scaled_max = false; calc_wb_limits(rwb); rwb_wake_all(rwb); } static bool close_io(struct rq_wb *rwb) { const unsigned long now = jiffies; return time_before(now, rwb->last_issue + HZ / 10) || time_before(now, rwb->last_comp + HZ / 10); } #define REQ_HIPRIO (REQ_SYNC | REQ_META | REQ_PRIO) static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw) { unsigned int limit; /* * At this point we know it's a buffered write. If this is * kswapd trying to free memory, or REQ_SYNC is set, set, then * it's WB_SYNC_ALL writeback, and we'll use the max limit for * that. If the write is marked as a background write, then use * the idle limit, or go to normal if we haven't had competing * IO for a bit. */ if ((rw & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd()) limit = rwb->wb_max; else if ((rw & REQ_BACKGROUND) || close_io(rwb)) { /* * If less than 100ms since we completed unrelated IO, * limit us to half the depth for background writeback. */ limit = rwb->wb_background; } else limit = rwb->wb_normal; return limit; } static inline bool may_queue(struct rq_wb *rwb, struct rq_wait *rqw, wait_queue_t *wait, unsigned long rw) { /* * inc it here even if disabled, since we'll dec it at completion. * this only happens if the task was sleeping in __wbt_wait(), * and someone turned it off at the same time. */ if (!rwb_enabled(rwb)) { atomic_inc(&rqw->inflight); return true; } /* * If the waitqueue is already active and we are not the next * in line to be woken up, wait for our turn. */ if (waitqueue_active(&rqw->wait) && rqw->wait.task_list.next != &wait->task_list) return false; return atomic_inc_below(&rqw->inflight, get_limit(rwb, rw)); } /* * Block if we will exceed our limit, or if we are currently waiting for * the timer to kick off queuing again. */ static void __wbt_wait(struct rq_wb *rwb, unsigned long rw, spinlock_t *lock) { struct rq_wait *rqw = get_rq_wait(rwb, current_is_kswapd()); DEFINE_WAIT(wait); if (may_queue(rwb, rqw, &wait, rw)) return; do { prepare_to_wait_exclusive(&rqw->wait, &wait, TASK_UNINTERRUPTIBLE); if (may_queue(rwb, rqw, &wait, rw)) break; if (lock) spin_unlock_irq(lock); io_schedule(); if (lock) spin_lock_irq(lock); } while (1); finish_wait(&rqw->wait, &wait); } static inline bool wbt_should_throttle(struct rq_wb *rwb, struct bio *bio) { const int op = bio_op(bio); /* * If not a WRITE (or a discard), do nothing */ if (!(op == REQ_OP_WRITE || op == REQ_OP_DISCARD)) return false; /* * Don't throttle WRITE_ODIRECT */ if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) == (REQ_SYNC | REQ_IDLE)) return false; return true; } /* * Returns true if the IO request should be accounted, false if not. * May sleep, if we have exceeded the writeback limits. Caller can pass * in an irq held spinlock, if it holds one when calling this function. * If we do sleep, we'll release and re-grab it. */ unsigned int wbt_wait(struct rq_wb *rwb, struct bio *bio, spinlock_t *lock) { unsigned int ret = 0; if (!rwb_enabled(rwb)) return 0; if (bio_op(bio) == REQ_OP_READ) ret = WBT_READ; if (!wbt_should_throttle(rwb, bio)) { if (ret & WBT_READ) wb_timestamp(rwb, &rwb->last_issue); return ret; } __wbt_wait(rwb, bio->bi_opf, lock); if (!timer_pending(&rwb->window_timer)) rwb_arm_timer(rwb); if (current_is_kswapd()) ret |= WBT_KSWAPD; return ret | WBT_TRACKED; } void wbt_issue(struct rq_wb *rwb, struct blk_issue_stat *stat) { if (!rwb_enabled(rwb)) return; /* * Track sync issue, in case it takes a long time to complete. Allows * us to react quicker, if a sync IO takes a long time to complete. * Note that this is just a hint. 'stat' can go away when the * request completes, so it's important we never dereference it. We * only use the address to compare with, which is why we store the * sync_issue time locally. */ if (wbt_is_read(stat) && !rwb->sync_issue) { rwb->sync_cookie = stat; rwb->sync_issue = blk_stat_time(stat); } } void wbt_requeue(struct rq_wb *rwb, struct blk_issue_stat *stat) { if (!rwb_enabled(rwb)) return; if (stat == rwb->sync_cookie) { rwb->sync_issue = 0; rwb->sync_cookie = NULL; } } void wbt_set_queue_depth(struct rq_wb *rwb, unsigned int depth) { if (rwb) { rwb->queue_depth = depth; wbt_update_limits(rwb); } } void wbt_set_write_cache(struct rq_wb *rwb, bool write_cache_on) { if (rwb) rwb->wc = write_cache_on; } void wbt_disable(struct rq_wb *rwb) { if (rwb) { del_timer_sync(&rwb->window_timer); rwb->win_nsec = rwb->min_lat_nsec = 0; wbt_update_limits(rwb); } } EXPORT_SYMBOL_GPL(wbt_disable); int wbt_init(struct request_queue *q) { struct rq_wb *rwb; int i; /* * For now, we depend on the stats window being larger than * our monitoring window. Ensure that this isn't inadvertently * violated. */ BUILD_BUG_ON(RWB_WINDOW_NSEC > BLK_STAT_NSEC); BUILD_BUG_ON(WBT_NR_BITS > BLK_STAT_RES_BITS); rwb = kzalloc(sizeof(*rwb), GFP_KERNEL); if (!rwb) return -ENOMEM; for (i = 0; i < WBT_NUM_RWQ; i++) { atomic_set(&rwb->rq_wait[i].inflight, 0); init_waitqueue_head(&rwb->rq_wait[i].wait); } setup_timer(&rwb->window_timer, wb_timer_fn, (unsigned long) rwb); rwb->wc = 1; rwb->queue_depth = RWB_DEF_DEPTH; rwb->last_comp = rwb->last_issue = jiffies; rwb->queue = q; rwb->win_nsec = RWB_WINDOW_NSEC; wbt_update_limits(rwb); /* * Assign rwb, and turn on stats tracking for this queue */ q->rq_wb = rwb; blk_stat_enable(q); if (blk_queue_nonrot(q)) rwb->min_lat_nsec = 2000000ULL; else rwb->min_lat_nsec = 75000000ULL; wbt_set_queue_depth(rwb, blk_queue_depth(q)); wbt_set_write_cache(rwb, test_bit(QUEUE_FLAG_WC, &q->queue_flags)); return 0; } void wbt_exit(struct request_queue *q) { struct rq_wb *rwb = q->rq_wb; if (rwb) { del_timer_sync(&rwb->window_timer); q->rq_wb = NULL; kfree(rwb); } }
generated by cgit v1.2.2 (git 2.25.0) at 2024-12-26 00:58:01 -0500