linux-kernel - Re: Possible bug report: kernel 6.5.0/6.5.1 high load when CIFS share is mounted (cifsd-cfid-laundromat in"D" state)

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Date:   Wed, 6 Sep 2023 08:01:51 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     Brian Pardy <brian.pardy@...il.com>,
        Linux CIFS <linux-cifs@...r.kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>,
        Steve French <sfrench@...ba.org>
Subject: Re: Possible bug report: kernel 6.5.0/6.5.1 high load when CIFS
 share is mounted (cifsd-cfid-laundromat in"D" state)

On Tue, Sep 05, 2023 at 01:09:05PM -0400, Brian Pardy wrote:
> My apologies if I do not have the bug report protocol correct in posting here.
> 
> I've noticed an issue with the CIFS client in kernel 6.5.0/6.5.1 that
> does not exist in 6.4.12 or other previous kernels (I have not tested
> 6.4.13). Almost immediately after mounting a CIFS share, the reported
> load average on my system goes up by 2. At the time this occurs I see
> two [cifsd-cfid-laundromat] kernel threads running the "D" state,
> where they remain for the entire time the CIFS share is mounted. The
> load will remain stable at 2 (otherwise idle) until the share is
> unmounted, at which point the [cifsd-cfid-laundromat] threads
> disappear and load drops back down to 0. This is easily reproducible
> on my system, but I am not sure what to do to retrieve more useful
> debugging information. If I mount two shares from this server, I get
> four laundromat threads in "D" state and a sustained load average of
> 4.
> 
> The client is running Gentoo Linux, the server is a Seagate Personal
> Cloud NAS running Samba 4.6.5. Mount options used are
> "noperm,guest,vers=3.02". The CPUs do not actually appear to be
> spinning, the reported load average appears incorrect as far as actual
> CPU use is concerned.
> 
> I am happy to follow any instructions provided to gather more details
> if I can help to track this down. Nothing that appears relevant
> appears in syslog or dmesg output.

Thanks for the regression report. But if you want to get it fixed,
you have to do your part: perform bisection. See Documentation/admin-guide/bug-bisect.rst in the kernel sources for how to do that.

Anyway, I'm adding it to regzbot:

#regzbot ^introduced: v6.4..v6.5
#regzbot title: incorrect CPU utilization report (multiplied) when mounting CIFS

Bye!

-- 
An old man doll... just what I always wanted! - Clara

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