Re: [PATCH v1 2/2] NFSD: Change the filecache laundrette workqueue again

[Jeff Layton <jlayton@kernel.org>]

On Thu, 2025-01-02 at 20:00 -0500, cel@kernel.org wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
> 
> Youzhong Yang <youzhong@gmail.com> noticed the workqueue subsystem
> complaining about how long the filecache laundrette was running.
> This resulted in switching from using the system_wq for the
> laundrette to system_unbound_wq (see commit 4b84551a35e3 ("nfsd: use
> system_unbound_wq for nfsd_file_gc_worker()").
> 
> However, I've seen the laundrette running for multiple milliseconds
> on some workloads, delaying other work. For the purpose of
> scheduling fairness, perhaps a better choice would be to process
> filecache disposal queues on the system_long_wq instead.
> 
> Cc: Tejun Heo <tj@kernel.org>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  fs/nfsd/filecache.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> index a1cdba42c4fa..91a535c2dede 100644
> --- a/fs/nfsd/filecache.c
> +++ b/fs/nfsd/filecache.c
> @@ -112,7 +112,7 @@ static void
>  nfsd_file_schedule_laundrette(void)
>  {
>  	if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags))
> -		queue_delayed_work(system_unbound_wq, &nfsd_filecache_laundrette,
> +		queue_delayed_work(system_long_wq, &nfsd_filecache_laundrette,
>  				   NFSD_LAUNDRETTE_DELAY);
>  }
>  

TIL that there is system_long_wq! Seems like a reasonable thing to do
since this is generally low-priority work.

Reviewed-by: Jeff Layton <jlayton@kernel.org>