linux-kernel - Re: [PATCH RFC v2 0/8] blk-mq: improve tag fair sharing

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Date:   Mon, 23 Oct 2023 12:38:03 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     bvanassche@....org, hch@....de, kbusch@...nel.org, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH RFC v2 0/8] blk-mq: improve tag fair sharing

Hello Yu Kuai,

On Sat, Oct 21, 2023 at 11:47:58PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> Current implementation:
>  - a counter active_queues record how many queue/hctx is sharing tags,
>  and it's updated while issue new IO, and cleared in
>  blk_mq_timeout_work().
>  - if active_queues is more than 1, then tags is fair shared to each
>  node;

Can you explain a bit what the problem is in current tag sharing?
And what is your basic approach for this problem?

Just mentioning the implementation is not too helpful for initial
review, cause the problem and approach(correctness) need to be
understood first.

Thanks, 
Ming