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Subject: Re: still seeing single client NFS4ERR_DELAY / CB_RECALL
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <20200817222034.GA6390@fieldses.org>
Date:   Tue, 18 Aug 2020 17:26:26 -0400
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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To:     Bruce Fields <bfields@fieldses.org>
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> On Aug 17, 2020, at 6:20 PM, Bruce Fields <bfields@fieldses.org> =
wrote:
>=20
> On Sun, Aug 16, 2020 at 04:46:00PM -0400, Chuck Lever wrote:
>=20
>> In order of application:
>>=20
>> 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.
>>=20
>> fd4f83fd7dfb ("nfsd: convert nfs4_file->fi_fds array to use =
nfsd_files")
>> Does not build
>>=20
>> 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
>>=20
>> Can you take a look and see if there's anything obvious?
>=20
> Unfortunately nothing about the file cache code is very obvious to me.
> I'm looking at it....
>=20
> It adds some new nfserr_jukebox returns in nfsd_file_acquire.  Those
> mostly look like kmalloc failures, the one I'm not sure about is the
> NFSD_FILE_HASHED check.
>=20
> Or maybe it's the lease break there.

nfsd_file_acquire() always calls fh_verify() before it invokes =
nfsd_open().
Replacing nfs4_get_vfs_file's nfsd_open() call with nfsd_file_acquire() =
adds
almost 10 million fh_verify() calls to my test run.

On my server, fh_verify() is quite expensive. Most of the cost is in the
prepare_creds() call.

--
Chuck Lever