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From:   Brian Pardy <brian.pardy@gmail.com>
Date:   Mon, 18 Sep 2023 18:55:58 -0400
Message-ID: <CAO+kfxTvA6N=i+jGf0XbSyqf85i=q+vR6R9d_42OWfM2sWWXaA@mail.gmail.com>
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)
To:     Bagas Sanjaya <bagasdotme@gmail.com>,
        Linux CIFS <linux-cifs@vger.kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Regressions <regressions@lists.linux.dev>,
        Steve French <sfrench@samba.org>
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On Wed, Sep 6, 2023 at 5:03=E2=80=AFPM Brian Pardy <brian.pardy@gmail.com> =
wrote:
> On Tue, Sep 5, 2023 at 9:01=E2=80=AFPM Bagas Sanjaya <bagasdotme@gmail.co=
m> wrote:
> > Thanks for the regression report. But if you want to get it fixed,
> > you have to do your part: perform bisection. See Documentation/admin-gu=
ide/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 moun=
ting CIFS
>
> Thank you for directing me to the bug-bisect documentation. Results below=
:
>
> # git bisect bad
> d14de8067e3f9653cdef5a094176d00f3260ab20 is the first bad commit
> commit d14de8067e3f9653cdef5a094176d00f3260ab20
> Author: Ronnie Sahlberg <lsahlber@redhat.com>
> Date:   Thu Jul 6 12:32:24 2023 +1000
>
>     cifs: Add a laundromat thread for cached directories
>
>     and drop cached directories after 30 seconds
>
>     Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
>     Signed-off-by: Steve French <stfrench@microsoft.com>
>
>  fs/smb/client/cached_dir.c | 67 ++++++++++++++++++++++++++++++++++++++++=
++++++
>  fs/smb/client/cached_dir.h |  1 +
>  2 files changed, 68 insertions(+)

Is there any further information I can provide to aid in debugging
this issue? Should I just expect incorrect load average reporting when
a CIFS share is mounted on any kernel >6.5.0?

I'm not clear on the value or necessity of this "laundromat thread" -
everything worked as expected before it was added - shall I just patch
it out of my kernel builds going forward if there is no interest in
fixing it? Is a .config option to disable it possible?