linux-kernel - Re: [PATCH block-5.18] Revert "block: inherit request start time from bio for BLK

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Message-Id: <165108909873.140853.15966713411862913960.b4-ty@kernel.dk>
Date:   Wed, 27 Apr 2022 13:51:38 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     tj@...nel.org
Cc:     linux-block@...r.kernel.org, saravanand@...com,
        chris.obbard@...labora.com, kernel-team@...com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH block-5.18] Revert "block: inherit request start time from bio for BLK_CGROUP"

On Wed, 27 Apr 2022 09:49:12 -1000, Tejun Heo wrote:
> This reverts commit 0006707723233cb2a9a23ca19fc3d0864835704c. It has a
> couple problems:
> 
> * bio_issue_time() is stored in bio->bi_issue truncated to 51 bits. This
>   overflows in slightly over 26 days. Setting rq->io_start_time_ns with it
>   means that io duration calculation would yield >26days after 26 days of
>   uptime. This, for example, confuses kyber making it cause high IO
>   latencies.
> 
> [...]

Applied, thanks!

[1/1] Revert "block: inherit request start time from bio for BLK_CGROUP"
      commit: 4cddeacad6d4b23493a108d0705e7d2ab89ba5a3

Best regards,
-- 
Jens Axboe