From 1668533d0bffd3f92f992dace9d62f223d27452d Mon Sep 17 00:00:00 2001
From: Yu Kuai <yukuai3@huawei.com>
Date: Sun, 9 Oct 2022 09:05:34 +0000
Subject: [PATCH] md/raid10: prevent unnecessary calls to wake_up() in fast
path
mainline inclusion
from md-next
commit 7fdc91928ac109d3d1468ad7f951deb29a375e3d
category: performance
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5PRMO
CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/song/md.git/commit/?h=md-next&id=7fdc91928ac109d3d1468ad7f951deb29a375e3d
--------------------------------
Currently, wake_up() is called unconditionally in fast path such as
raid10_make_request(), which will cause lock contention under high
concurrency:
raid10_make_request
wake_up
__wake_up_common_lock
spin_lock_irqsave
Improve performance by only call wake_up() if waitqueue is not empty.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Song Liu <song@kernel.org>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
---
drivers/md/raid10.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 5049c4d829e5..13e0b4a462fc 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -305,6 +305,12 @@ static void put_buf(struct r10bio *r10_bio)
lower_barrier(conf);
}
+static void wake_up_barrier(struct r10conf *conf)
+{
+ if (wq_has_sleeper(&conf->wait_barrier))
+ wake_up(&conf->wait_barrier);
+}
+
static void reschedule_retry(struct r10bio *r10_bio)
{
unsigned long flags;
@@ -1025,7 +1031,7 @@ static void allow_barrier(struct r10conf *conf)
{
if ((atomic_dec_and_test(&conf->nr_pending)) ||
(conf->array_freeze_pending))
- wake_up(&conf->wait_barrier);
+ wake_up_barrier(conf);
}
static void freeze_array(struct r10conf *conf, int extra)
@@ -1584,7 +1590,7 @@ static bool raid10_make_request(struct mddev *mddev, struct bio *bio)
__make_request(mddev, bio, sectors);
/* In case raid10d snuck in to freeze_array */
- wake_up(&conf->wait_barrier);
+ wake_up_barrier(conf);
return true;
}
--
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