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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Message-ID: <c88b2ecd27524153c2acd8aba6ae3c80@matoro.tk>
Date:   Fri, 13 Oct 2023 20:59:26 -0400
From:   matoro <matoro_mailinglist_kernel@...oro.tk>
To:     Steve French <smfrench@...il.com>
Cc:     Paulo Alcantara <pc@...guebit.com>,
        "Dr. Bernd Feige" <bernd.feige@...klinik-freiburg.de>,
        Tom Talpey <tom@...pey.com>, Paul Aurich <paul@...krain42.org>,
        CIFS <linux-cifs@...r.kernel.org>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Linux Regressions <regressions@...ts.linux.dev>,
        ronnie sahlberg <ronniesahlberg@...il.com>,
        Shyam Prasad N <nspmangalore@...il.com>,
        Brian Pardy <brian.pardy@...il.com>,
        Bharath S M <bharathsm@...rosoft.com>,
        LKML <linux-kernel@...r.kernel.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 2023-10-13 20:13, Steve French wrote:
> Let me know if those fixes help as two of them have not been sent to 
> Linus
> yet, but I could send tomorrow
> 
> On Fri, Oct 13, 2023, 19:01 Paulo Alcantara <pc@...guebit.com> wrote:
> 
>> You probably want these two as well
>> 
>> 
>> https://git.samba.org/?p=sfrench/cifs-2.6.git;a=commit;h=2da338ff752a2789470d733111a5241f30026675
>> 
>> 
>> https://git.samba.org/?p=sfrench/cifs-2.6.git;a=commit;h=3b8bb3171571f92eda863e5f78b063604c61f72a
>> 
>> as directory leases isn't supported in SMB1, so no waste of system
>> resources by having those kthreads running.
>> 
>> On 13 October 2023 20:52:11 GMT-03:00, Paulo Alcantara 
>> <pc@...guebit.com>
>> wrote:
>> >Could you please try two commits[1][2] from for-next?
>> >
>> >[1]
>> https://git.samba.org/?p=sfrench/cifs-2.6.git;a=commit;h=e95f3f74465072c2545d8e65a3c3a96e37129cf8
>> >[2]
>> https://git.samba.org/?p=sfrench/cifs-2.6.git;a=commit;h=81ba10959970d15c388bf29866b01b62f387e6a3
>> >
>> >On 13 October 2023 20:19:37 GMT-03:00, matoro <
>> matoro_mailinglist_kernel@...oro.tk> wrote:
>> >>On 2023-10-05 05:55, Dr. Bernd Feige wrote:
>> >>> Am Dienstag, dem 26.09.2023 um 17:54 -0700 schrieb Paul Aurich:
>> >>>> Perhaps the laundromat thread should be using msleep_interruptible()?
>> >>>>
>> >>>> Using an interruptible sleep appears to prevent the thread from
>> >>>> contributing
>> >>>> to the load average, and has the happy side-effect of removing the
>> >>>> up-to-1s delay
>> >>>> when tearing down the tcon (since a7c01fa93ae, kthread_stop() will
>> >>>> return
>> >>>> early triggered by kthread_stop).
>> >>>
>> >>> Sorry for chiming in so late - I'm also on gentoo (kernel 6.5.5-
>> >>> gentoo), but as a client of Windows AD.
>> >>>
>> >>> Just want to emphasize that using uninterruptible sleep has not just
>> >>> unhappy but devastating side-effects.
>> >>>
>> >>> I have 8 processors and 16 cifsd-cfid-laundromat processes, so
>> >>> /proc/loadavg reports a load average of 16 on a totally idle system.
>> >>>
>> >>> This means that load-balancing software will never start additional
>> >>> tasks on this system - "make -l" but also any other load-dependent
>> >>> system. Just reducing the number of cifsd-cfid-laundromat processes
>> >>> does not fix this - even a single one makes loadavg report a wrong
>> >>> result for load balancing.
>> >>>
>> >>> So, if cifsd-cfid-laundromat must really be uninterruptible, the only
>> >>> solution would be to change the way loadavg is computed by the kernel
>> >>> to exclude uninterruptible but sleeping processes. But must it be
>> >>> uninterruptible?
>> >>>
>> >>> Thanks and best regards,
>> >>> Bernd
>> >>
>> >>This is a huge problem here as well, as a client to Samba using SMB1
>> (for Unix extensions).
>> >>
>> >>For others encountering this problem, I was able to work around it with
>> the following snippet:
>> >>
>> >>diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
>> >>index 2d5e9a9d5b8b..fc2caccb597a 100644
>> >>--- a/fs/smb/client/cached_dir.c
>> >>+++ b/fs/smb/client/cached_dir.c
>> >>@@ -576,7 +576,7 @@ cifs_cfids_laundromat_thread(void *p)
>> >>        struct list_head entry;
>> >>
>> >>        while (!kthread_should_stop()) {
>> >>-               ssleep(1);
>> >>+               msleep_interruptible(1000);
>> >>                INIT_LIST_HEAD(&entry);
>> >>                if (kthread_should_stop())
>> >>                        return 0;
>> 

Do you have backports of these to 6.5?  I tried to do it manually but 
there's already so many changes between 6.5 and these commits.