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Subject: Re: still seeing single client NFS4ERR_DELAY / CB_RECALL
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <CA3288FC-8B9A-4F19-A51C-E1169726E946@oracle.com>
Date:   Sun, 16 Aug 2020 16:46:00 -0400
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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To:     Bruce Fields <bfields@fieldses.org>
Sender: linux-nfs-owner@vger.kernel.org
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Hi Bruce-

> On Aug 11, 2020, at 9:31 AM, Chuck Lever <chuck.lever@oracle.com> wrote:
> 
>> On Aug 10, 2020, at 4:10 PM, Bruce Fields <bfields@fieldses.org> wrote:
>> 
>> On Mon, Aug 10, 2020 at 04:01:00PM -0400, Chuck Lever wrote:
>>> Roughly the same result with this patch as with the first one. The
>>> first one is a little better. Plus, I think the Solaris NFS server
>>> hands out write delegations on v4.0, and I haven't heard of a
>>> significant issue there. It's heuristics may be different, though.
>>> 
>>> So, it might be that NFSv4.0 has always run significantly slower. I
>>> will have to try a v5.4 or older server to see.
>> 
>> Oh, OK, I was assuming this was a regression.
> 
> Me too. Looks like it is: NFSv4.0 always runs slower, but I see
> it get significantly worse between v5.4 and 5.5. I will post more
> quantified results soon.

It took me a while to get plausible bisection results. The problem
appears in the midst of the NFSD filecache patches merged in v5.4.

In order of application:

5920afa3c85f ("nfsd: hook nfsd_commit up to the nfsd_file cache")
961.68user 5252.40system 20:12.30elapsed 512%CPU, 2541 DELAY errors
These results are similar to v5.3.

fd4f83fd7dfb ("nfsd: convert nfs4_file->fi_fds array to use nfsd_files")
Does not build

eb82dd393744 ("nfsd: convert fi_deleg_file and ls_file fields to nfsd_file")
966.92user 5425.47system 33:52.79elapsed 314%CPU, 1330 DELAY errors

Can you take a look and see if there's anything obvious?


--
Chuck Lever