Re: still seeing single client NFS4ERR_DELAY / CB_RECALL

[Chuck Lever <chuck.lever@oracle.com>]

> On Aug 17, 2020, at 6:20 PM, Bruce Fields <bfields@fieldses.org> wrote:
> 
> On Sun, Aug 16, 2020 at 04:46:00PM -0400, Chuck Lever wrote:
>> 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.
> 
> Well, that's interesting.
> 
>> 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

Quick follow-up:

I reverted a couple of hunks that appear to be for the next commit,
and fd4f83fd7dfb builds now. Tested, and this is the bad commit (where
the performance regression starts).


>> 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?
> 
> Unfortunately nothing about the file cache code is very obvious to me.
> I'm looking at it....
> 
> 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.
> 
> Or maybe it's the lease break there.
> 
> --b.

--
Chuck Lever