On Mon, 2022-11-07 at 15:11 +0000, Chuck Lever III wrote:

Hi Jeff -

quoted

On Nov 7, 2022, at 10:01 AM, Jeff Layton [off-list ref] wrote:

nfsd has grown a dedicated workqueue for the filecache, but this job is
still queued to the system_wq. Change it to use the filecache_wq.

Actually... there doesn't seem to be anything special about
nfsd_filecache_wq. 9542e6a643fc ("nfsd: Containerise filecache
laundrette") does not make clear why it was added.

Playing devil's advocate: why not make the converse change and
replace it with system_wq?

Good question.

At one time, allocating a workqueue gave you a dedicated pool of
threads, but that's no longer the case.

Documentation/core-api/workqueue.rst says: "A wq no longer manages
execution resources but serves as a domain for forward progress
guarantee, flush and work item attributes."

Given that we're allocating this workqueue exactly the same way we
allocate the system_wq, I don't think we need our own workqueue at all.
I'd be fine with changing this to be the reverse if you prefer.

quoted

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
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 1e76b0d3b83a..018fd1565193 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c

@@ -212,7 +212,7 @@ static void

nfsd_file_schedule_laundrette(void)
{
	if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags))
-		queue_delayed_work(system_wq, &nfsd_filecache_laundrette,
+		queue_delayed_work(nfsd_filecache_wq, &nfsd_filecache_laundrette,
				   NFSD_LAUNDRETTE_DELAY);
}

-- 
2.38.1

--
Chuck Lever

-- 
Jeff Layton [off-list ref]