> On May 11, 2022, at 8:38 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, May 11, 2022 at 12:03:13PM +0200, Wolfgang Walter wrote:
>> Hi,
>>
>> starting with 5.4.188 wie see a massive performance regression on our
>> nfs-server. It basically is serving requests very very slowly with cpu
>> utilization of 100% (with 5.4.187 and earlier it is 10%) so that it is
>> unusable as a fileserver.
>>
>> The culprit are commits (or one of it):
>>
>> c32f1041382a88b17da5736886da4a492353a1bb "nfsd: cleanup
>> nfsd_file_lru_dispose()"
>> 628adfa21815f74c04724abc85847f24b5dd1645 "nfsd: Containerise filecache
>> laundrette"
>>
>> (upstream 36ebbdb96b694dd9c6b25ad98f2bbd263d022b63 and
>> 9542e6a643fc69d528dfb3303f145719c61d3050)
>>
>> If I revert them in v5.4.192 the kernel works as before and performance is
>> ok again.
>>
>> I did not try to revert them one by one as any disruption of our nfs-server
>> is a severe problem for us and I'm not sure if they are related.
>>
>> 5.10 and 5.15 both always performed very badly on our nfs-server in a
>> similar way so we were stuck with 5.4.
>>
>> I now think this is because of 36ebbdb96b694dd9c6b25ad98f2bbd263d022b63
>> and/or 9542e6a643fc69d528dfb3303f145719c61d3050 though I didn't tried to
>> revert them in 5.15 yet.
>
> Odds are 5.18-rc6 is also a problem?
We believe that
6b8a94332ee4 ("nfsd: Fix a write performance regression")
addresses the performance regression. It was merged into 5.18-rc.
> If so, I'll just wait for the fix to get into Linus's tree as this does
> not seem to be a stable-tree-only issue.
Unfortunately I've received a recent report that the fix introduces
a "sleep while spinlock is held" for NFSv4.0 in rare cases.
--
Chuck Lever
