Re: [PATCH] blk-mq: plug request for shared sbitmap
From: Jens Axboe <axboe@kernel.dk>
Date: 2021-05-14 14:59:22
On 5/13/21 8:20 PM, Ming Lei wrote:
In case of shared sbitmap, request won't be held in plug list any more
sine commit 32bc15afed04 ("blk-mq: Facilitate a shared sbitmap per
tagset"), this way makes request merge from flush plug list & batching
submission not possible, so cause performance regression.
Yanhui reports performance regression when running sequential IO
test(libaio, 16 jobs, 8 depth for each job) in VM, and the VM disk
is emulated with image stored on xfs/megaraid_sas.
Fix the issue by recovering original behavior to allow to hold request
in plug list.Applied, thanks. -- Jens Axboe