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:   Tue, 19 Sep 2023 00:36:07 -0500
From:   Steve French <smfrench@...il.com>
To:     Brian Pardy <brian.pardy@...il.com>
Cc:     Bagas Sanjaya <bagasdotme@...il.com>,
        Linux CIFS <linux-cifs@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>,
        Paulo Alcantara <pc@...guebit.com>,
        ronnie sahlberg <ronniesahlberg@...il.com>,
        Shyam Prasad N <nspmangalore@...il.com>,
        Bharath S M <bharathsm@...rosoft.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)

Does the attached patch help in your case?  It avoids starting the
laundromat thread for IPC shares (which cuts the number of the threads
in half for many cases) and also avoids starting them if the server
does not support directory leases (e.g. if Samba server instead of
Windows server).


On Mon, Sep 18, 2023 at 10:00 PM Steve French <smfrench@...il.com> wrote:
>
> Paulo and I were discussing the laundromat thread at the SMB3.1.1 test
> event (at SDC this week) which is now going on - will let you know
> what we find.
>
> One obvious thing is that it probably isn't necessary for cases when
> the server does not support directory leases, but we noticed another
> problem as well.
>
>
> On Mon, Sep 18, 2023 at 9:20 PM Brian Pardy <brian.pardy@...il.com> wrote:
> >
> > [RS removed from CC due to bounce message]
> >
> > On Wed, Sep 6, 2023 at 5:03 PM Brian Pardy <brian.pardy@...il.com> wrote:
> > > On Tue, Sep 5, 2023 at 9:01 PM Bagas Sanjaya <bagasdotme@...il.com> 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-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
> > >
> > > 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@...hat.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@...hat.com>
> > >     Signed-off-by: Steve French <stfrench@...rosoft.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?
>
>
>
> --
> Thanks,
>
> Steve



-- 
Thanks,

Steve

View attachment "0001-smb3-do-not-start-laundromat-thread-when-dir-leases-.patch" of type "text/x-patch" (4926 bytes)