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: <ZRN9MtBqYnT6oX60@vaarsuvius>
Date:   Tue, 26 Sep 2023 17:54:10 -0700
From:   Paul Aurich <paul@...krain42.org>
To:     Steve French <smfrench@...il.com>, Tom Talpey <tom@...pey.com>
Cc:     Brian Pardy <brian.pardy@...il.com>,
        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)

On 2023-09-19 13:23:44 -0500, Steve French wrote:
>On Tue, Sep 19, 2023 at 1:07 PM Tom Talpey <tom@...pey.com> wrote:
>> These changes are good, but I'm skeptical they will reduce the load
>> when the laundromat thread is actually running. All these do is avoid
>> creating it when not necessary, right?
>
>It does create half as many laundromat threads (we don't need
>laundromat on connection to IPC$) even for the Windows server target
>example, but helps more for cases where server doesn't support
>directory leases.

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).

~Paul