Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755206AbbDXNho (ORCPT ); Fri, 24 Apr 2015 09:37:44 -0400 Received: from mga09.intel.com ([134.134.136.24]:11729 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753654AbbDXNhk (ORCPT ); Fri, 24 Apr 2015 09:37:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,640,1422950400"; d="scan'208";a="714976037" From: Yuanhan Liu To: neilb@suse.de Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, Yuanhan Liu Subject: [PATCH 2/2] md/raid5: exclusive wait_for_stripe Date: Fri, 24 Apr 2015 21:39:04 +0800 Message-Id: <1429882744-22655-2-git-send-email-yuanhan.liu@linux.intel.com> X-Mailer: git-send-email 1.9.0 In-Reply-To: <1429882744-22655-1-git-send-email-yuanhan.liu@linux.intel.com> References: <1429882744-22655-1-git-send-email-yuanhan.liu@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9516 Lines: 209 I noticed heavy spin lock contention at get_active_stripe() with fsmark multiple thread write workloads. Here is how this hot contention comes from. We have limited stripes, and it's a multiple thread write workload. Hence, those stripes will be taken soon, which puts later processes to sleep for waiting free stripes. When enough stripes(> 1/4 total stripes) are released, all process are woken, trying to get the lock. But there is one only being able to get this lock for each hash lock, making other processes spinning out there for acquiring the lock. Thus, it's effectiveless to wakeup all processes and let them battle for a lock that permits one to access only each time. Instead, we could make it be a exclusive wake up: wake up one process only. That avoids the heavy spin lock contention naturally. Here are some test results I have got with this patch applied(all test run 3 times): `fsmark.files_per_sec' ===================== next-20150317 this patch ------------------------- ------------------------- metric_value ±stddev metric_value ±stddev change testbox/benchmark/testcase-params ------------------------- ------------------------- -------- ------------------------------ 25.600 ±0.0 92.700 ±2.5 262.1% ivb44/fsmark/1x-64t-4BRD_12G-RAID5-btrfs-4M-30G-fsyncBeforeClose 25.600 ±0.0 77.800 ±0.6 203.9% ivb44/fsmark/1x-64t-9BRD_6G-RAID5-btrfs-4M-30G-fsyncBeforeClose 32.000 ±0.0 93.800 ±1.7 193.1% ivb44/fsmark/1x-64t-4BRD_12G-RAID5-ext4-4M-30G-fsyncBeforeClose 32.000 ±0.0 81.233 ±1.7 153.9% ivb44/fsmark/1x-64t-9BRD_6G-RAID5-ext4-4M-30G-fsyncBeforeClose 48.800 ±14.5 99.667 ±2.0 104.2% ivb44/fsmark/1x-64t-4BRD_12G-RAID5-xfs-4M-30G-fsyncBeforeClose 6.400 ±0.0 12.800 ±0.0 100.0% ivb44/fsmark/1x-64t-3HDD-RAID5-btrfs-4M-40G-fsyncBeforeClose 63.133 ±8.2 82.800 ±0.7 31.2% ivb44/fsmark/1x-64t-9BRD_6G-RAID5-xfs-4M-30G-fsyncBeforeClose 245.067 ±0.7 306.567 ±7.9 25.1% ivb44/fsmark/1x-64t-4BRD_12G-RAID5-f2fs-4M-30G-fsyncBeforeClose 17.533 ±0.3 21.000 ±0.8 19.8% ivb44/fsmark/1x-1t-3HDD-RAID5-xfs-4M-40G-fsyncBeforeClose 188.167 ±1.9 215.033 ±3.1 14.3% ivb44/fsmark/1x-1t-4BRD_12G-RAID5-btrfs-4M-30G-NoSync 254.500 ±1.8 290.733 ±2.4 14.2% ivb44/fsmark/1x-1t-9BRD_6G-RAID5-btrfs-4M-30G-NoSync `time.system_time' ===================== next-20150317 this patch ------------------------- ------------------------- metric_value ±stddev metric_value ±stddev change testbox/benchmark/testcase-params ------------------------- ------------------------- -------- ------------------------------ 7235.603 ±1.2 185.163 ±1.9 -97.4% ivb44/fsmark/1x-64t-4BRD_12G-RAID5-btrfs-4M-30G-fsyncBeforeClose 7666.883 ±2.9 202.750 ±1.0 -97.4% ivb44/fsmark/1x-64t-9BRD_6G-RAID5-btrfs-4M-30G-fsyncBeforeClose 14567.893 ±0.7 421.230 ±0.4 -97.1% ivb44/fsmark/1x-64t-3HDD-RAID5-btrfs-4M-40G-fsyncBeforeClose 3697.667 ±14.0 148.190 ±1.7 -96.0% ivb44/fsmark/1x-64t-4BRD_12G-RAID5-xfs-4M-30G-fsyncBeforeClose 5572.867 ±3.8 310.717 ±1.4 -94.4% ivb44/fsmark/1x-64t-9BRD_6G-RAID5-ext4-4M-30G-fsyncBeforeClose 5565.050 ±0.5 313.277 ±1.5 -94.4% ivb44/fsmark/1x-64t-4BRD_12G-RAID5-ext4-4M-30G-fsyncBeforeClose 2420.707 ±17.1 171.043 ±2.7 -92.9% ivb44/fsmark/1x-64t-9BRD_6G-RAID5-xfs-4M-30G-fsyncBeforeClose 3743.300 ±4.6 379.827 ±3.5 -89.9% ivb44/fsmark/1x-64t-3HDD-RAID5-ext4-4M-40G-fsyncBeforeClose 3308.687 ±6.3 363.050 ±2.0 -89.0% ivb44/fsmark/1x-64t-3HDD-RAID5-xfs-4M-40G-fsyncBeforeClose Where, 1x: where 'x' means iterations or loop, corresponding to the 'L' option of fsmark 1t, 64t: where 't' means thread 4M: means the single file size, corresponding to the '-s' option of fsmark 40G, 30G, 120G: means the total test size 4BRD_12G: BRD is the ramdisk, where '4' means 4 ramdisk, and where '12G' means the size of one ramdisk. So, it would be 48G in total. And we made a raid on those ramdisk As you can see, though there are no much performance gain for hard disk workload, the system time is dropped heavily, up to 97%. And as expected, the performance increased a lot, up to 260%, for fast device(ram disk). Signed-off-by: Yuanhan Liu --- drivers/md/raid5.c | 46 +++++++++++++++++++++++++++++++++++----------- drivers/md/raid5.h | 2 +- 2 files changed, 36 insertions(+), 12 deletions(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index b7e385f..2d8fcc1 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -344,7 +344,8 @@ static void release_inactive_stripe_list(struct r5conf *conf, int hash) { int size; - bool do_wakeup = false; + bool do_wakeup[NR_STRIPE_HASH_LOCKS] = { false, }; + int i = 0; unsigned long flags; if (hash == NR_STRIPE_HASH_LOCKS) { @@ -365,17 +366,22 @@ static void release_inactive_stripe_list(struct r5conf *conf, !list_empty(list)) atomic_dec(&conf->empty_inactive_list_nr); list_splice_tail_init(list, conf->inactive_list + hash); - do_wakeup = true; + do_wakeup[size - 1] = true; spin_unlock_irqrestore(conf->hash_locks + hash, flags); } size--; hash--; } - if (do_wakeup) { - wake_up(&conf->wait_for_stripe); - if (conf->retry_read_aligned) - md_wakeup_thread(conf->mddev->thread); + for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++) { + bool waked_thread = false; + if (do_wakeup[i]) { + wake_up(&conf->wait_for_stripe[i]); + if (!waked_thread) { + waked_thread = true; + md_wakeup_thread(conf->mddev->thread); + } + } } } @@ -655,6 +661,18 @@ static int has_failed(struct r5conf *conf) return 0; } +/* XXX: might put it to linux/wait.h to be a public API? */ +#define raid_wait_event_exclusive_cmd(wq, condition, cmd1, cmd2) \ +do { \ + if (condition) \ + break; \ + (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 1, 0, \ + cmd1; \ + schedule(); \ + cmd2); \ +} while (0) + + static struct stripe_head * get_active_stripe(struct r5conf *conf, sector_t sector, int previous, int noblock, int noquiesce) @@ -684,14 +702,15 @@ get_active_stripe(struct r5conf *conf, sector_t sector, if (!sh) { set_bit(R5_INACTIVE_BLOCKED, &conf->cache_state); - wait_event_lock_irq( - conf->wait_for_stripe, + raid_wait_event_exclusive_cmd( + conf->wait_for_stripe[hash], !list_empty(conf->inactive_list + hash) && (atomic_read(&conf->active_stripes) < (conf->max_nr_stripes * 3 / 4) || !test_bit(R5_INACTIVE_BLOCKED, &conf->cache_state)), - *(conf->hash_locks + hash)); + spin_unlock_irq(conf->hash_locks + hash), + spin_lock_irq(conf->hash_locks + hash)); clear_bit(R5_INACTIVE_BLOCKED, &conf->cache_state); } else { @@ -716,6 +735,9 @@ get_active_stripe(struct r5conf *conf, sector_t sector, } } while (sh == NULL); + if (!list_empty(conf->inactive_list + hash)) + wake_up(&conf->wait_for_stripe[hash]); + spin_unlock_irq(conf->hash_locks + hash); return sh; } @@ -2136,7 +2158,7 @@ static int resize_stripes(struct r5conf *conf, int newsize) cnt = 0; list_for_each_entry(nsh, &newstripes, lru) { lock_device_hash_lock(conf, hash); - wait_event_cmd(conf->wait_for_stripe, + raid_wait_event_exclusive_cmd(conf->wait_for_stripe[hash], !list_empty(conf->inactive_list + hash), unlock_device_hash_lock(conf, hash), lock_device_hash_lock(conf, hash)); @@ -6391,7 +6413,9 @@ static struct r5conf *setup_conf(struct mddev *mddev) spin_lock_init(&conf->device_lock); seqcount_init(&conf->gen_lock); init_waitqueue_head(&conf->wait_for_quiesce); - init_waitqueue_head(&conf->wait_for_stripe); + for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++) { + init_waitqueue_head(&conf->wait_for_stripe[i]); + } init_waitqueue_head(&conf->wait_for_overlap); INIT_LIST_HEAD(&conf->handle_list); INIT_LIST_HEAD(&conf->hold_list); diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h index fab53a3..cdad2d2 100644 --- a/drivers/md/raid5.h +++ b/drivers/md/raid5.h @@ -509,7 +509,7 @@ struct r5conf { atomic_t empty_inactive_list_nr; struct llist_head released_stripes; wait_queue_head_t wait_for_quiesce; - wait_queue_head_t wait_for_stripe; + wait_queue_head_t wait_for_stripe[NR_STRIPE_HASH_LOCKS]; wait_queue_head_t wait_for_overlap; unsigned long cache_state; #define R5_INACTIVE_BLOCKED 1 /* release of inactive stripes blocked, -- 1.9.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/