linux-kernel - [PATCH -next v2 5/5] block, bfq: do not idle if only one cgroup is activated

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Date:   Sat, 16 Apr 2022 17:37:53 +0800
From:   Yu Kuai <yukuai3@...wei.com>
To:     <jack@...e.cz>, <paolo.valente@...aro.org>, <axboe@...nel.dk>,
        <tj@...nel.org>
CC:     <linux-block@...r.kernel.org>, <cgroups@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <yukuai3@...wei.com>,
        <yi.zhang@...wei.com>
Subject: [PATCH -next v2 5/5] block, bfq: do not idle if only one cgroup is activated

Now that root group is counted into 'num_groups_with_pending_reqs',
'num_groups_with_pending_reqs > 0' is always true in
bfq_asymmetric_scenario().

Thus change the condition to 'num_groups_with_pending_reqs > 1'.

On the other hand, now that 'num_groups_with_pending_reqs' represents
how many groups have pending requests, this change can enable concurrent
sync io is only on cgroup is activated.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/bfq-iosched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 39abcd95df8e..7d9f94882f8e 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -846,7 +846,7 @@ static bool bfq_asymmetric_scenario(struct bfq_data *bfqd,
 
 	return varied_queue_weights || multiple_classes_busy
 #ifdef CONFIG_BFQ_GROUP_IOSCHED
-	       || bfqd->num_groups_with_pending_reqs > 0
+	       || bfqd->num_groups_with_pending_reqs > 1
 #endif
 		;
 }
-- 
2.31.1