From: Dave Chinner <david@fromorbit.com>
To: Anton Gavriliuk <antosha20xx@gmail.com>
Cc: Laurence Oberman <loberman@redhat.com>,
linux-nvme@lists.infradead.org, linux-xfs@vger.kernel.org,
linux-block@vger.kernel.org
Subject: Re: Sequential read from NVMe/XFS twice slower on Fedora 42 than on Rocky 9.5
Date: Thu, 8 May 2025 07:59:28 +1000 [thread overview]
Message-ID: <aBvXwComvV-uAqmb@dread.disaster.area> (raw)
In-Reply-To: <CAAiJnjp6WuVaxXbjndF8dB3fuWCuWz7Nqzpz0uEu2BOqyZUQHg@mail.gmail.com>
On Wed, May 07, 2025 at 03:26:08PM +0300, Anton Gavriliuk wrote:
> > `iostat -dxm 5` output during the fio run on both kernels will give us some indication of the differences in IO patterns, queue depths, etc.
>
> iostat files attached.
Yeah, that definitely looks like MD is the bottleneck. In both
traces the NVMe drives are completing read IOs in about 110-120us.
In fedora 42, the nvme drives are not at 100% utilisation so the md
device is not feeding them fast enough.
That can also be seen in that the rocky 9.5 kernel with a nvme
device queue depth of about 4 IOs, whilst it is only 1.5 for the
fedora 42 kernel.
Given that nobody from the block/MD side of things has responded
with any ideas yet, you might just have to bisect it to find out
where things went wrong...
-Dave.
--
Dave Chinner
david@fromorbit.com
prev parent reply other threads:[~2025-05-07 21:59 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAAiJnjoo0--yp47UKZhbu8sNSZN6DZ-QzmZBMmtr1oC=fOOgAQ@mail.gmail.com>
[not found] ` <aBaVsli2AKbIa4We@dread.disaster.area>
[not found] ` <CAAiJnjor+=Zn62n09f-aJw2amX2wxQOb-2TB3rea9wDCU7ONoA@mail.gmail.com>
2025-05-04 21:50 ` Sequential read from NVMe/XFS twice slower on Fedora 42 than on Rocky 9.5 Dave Chinner
2025-05-05 12:29 ` Laurence Oberman
2025-05-05 13:21 ` Laurence Oberman
2025-05-05 17:39 ` Laurence Oberman
2025-05-22 15:07 ` Laurence Oberman
2025-05-23 9:39 ` Anton Gavriliuk
2025-05-05 22:56 ` Dave Chinner
2025-05-06 11:03 ` Anton Gavriliuk
2025-05-06 21:46 ` Dave Chinner
2025-05-07 12:26 ` Anton Gavriliuk
2025-05-07 21:59 ` Dave Chinner [this message]
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