linux-kernel - [PATCH] blk-cgroup: don't account iostat for root cgroup

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Message-Id: <20200601231141.2218370-1-boris@bur.io>
Date:   Mon,  1 Jun 2020 16:11:41 -0700
From:   Boris Burkov <boris@....io>
To:     Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>
Cc:     cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...com,
        Boris Burkov <boris@....io>
Subject: [PATCH] blk-cgroup: don't account iostat for root cgroup

This data is never flushed by rstat, so it is never used. We shouldn't
bother collecting it. We can access global disk stats to compute io
statistics for the root cgroup.

Signed-off-by: Boris Burkov <boris@....io>
---
 include/linux/blk-cgroup.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index a57ebe2f00ab..e9de4ec07182 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -591,7 +591,7 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q,
 
 	throtl = blk_throtl_bio(q, blkg, bio);
 
-	if (!throtl) {
+	if (blkg->parent && !throtl) {
 		struct blkg_iostat_set *bis;
 		int rwd, cpu;
 
-- 
2.24.1