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: <E1F307C7-9B1E-40F6-860B-6050856E8395@manguebit.com>
Date:   Fri, 13 Oct 2023 20:52:11 -0300
From:   Paulo Alcantara <pc@...guebit.com>
To:     matoro <matoro_mailinglist_kernel@...oro.tk>,
        "Dr. Bernd Feige" <bernd.feige@...klinik-freiburg.de>
CC:     tom@...pey.com, smfrench@...il.com, paul@...krain42.org,
        linux-cifs@...r.kernel.org, bagasdotme@...il.com,
        regressions@...ts.linux.dev, ronniesahlberg@...il.com,
        nspmangalore@...il.com, brian.pardy@...il.com,
        bharathsm@...rosoft.com, 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)

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;