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From:   Yu Kuai <yukuai3@huawei.com>
To:     <jack@suse.cz>, <paolo.valente@linaro.org>, <axboe@kernel.dk>,
        <tj@kernel.org>
CC:     <linux-block@vger.kernel.org>, <cgroups@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <yukuai3@huawei.com>,
        <yi.zhang@huawei.com>
Subject: [PATCH -next v5 3/3] block, bfq: do not idle if only one group is activated
Date:   Thu, 28 Apr 2022 20:08:37 +0800
Message-ID: <20220428120837.3737765-4-yukuai3@huawei.com>
In-Reply-To: <20220428120837.3737765-1-yukuai3@huawei.com>
References: <20220428120837.3737765-1-yukuai3@huawei.com>
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Now that root group is counted into 'num_groups_with_busy_queues',
'num_groups_with_busy_queues > 0' is always true in
bfq_asymmetric_scenario(). Thus change the condition to '> 1'.

On the other hand, this change can enable concurrent sync io if only
one group is activated.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 block/bfq-iosched.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 609b4e894684..142e1ca4600f 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -812,7 +812,7 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq)
  * much easier to maintain the needed state:
  * 1) all active queues have the same weight,
  * 2) all active queues belong to the same I/O-priority class,
- * 3) there are no active groups.
+ * 3) there are one active group at most.
  * In particular, the last condition is always true if hierarchical
  * support or the cgroups interface are not enabled, thus no state
  * needs to be maintained in this case.
@@ -844,7 +844,7 @@ 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_busy_queues > 0
+	       || bfqd->num_groups_with_busy_queues > 1
 #endif
 		;
 }
-- 
2.31.1