Re: [PATCH v4 2/2] NFSD: add shrinker to reap courtesy clients on low memory condition

[dai.ngo@oracle.com]

On 9/6/22 6:00 AM, J. Bruce Fields wrote:
> On Sat, Sep 03, 2022 at 10:59:17AM -0700, dai.ngo@oracle.com wrote:
>> On 9/3/22 10:29 AM, Chuck Lever III wrote:
>>> What I was suggesting was a longer term strategy for improving the
>>> laundromat. In order to scale well in the number of clients, it
>>> needs to schedule client expiry and deletion without serializing.
>>>
>>> (ie, the laundromat itself can identify a set of clients to clean,
>>> but then it should pass that list to other workers so it can run
>>> again as soon as it needs to -- and that also means it can use more
>>> than just one CPU at a time to do its work).
>> I see. Currently on my lowly 1-CPU VM it takes about ~35 secs to
>> destroy 128 clients, each with only few states (generated by pynfs's
>> CID5 test). We can improve on this.
> Careful--it's not the CPU that's the issue, it's waiting for disk.
>
> If you're on a hard drive, for example, it's going to take at least one
> seek (probably at least 10ms) to expire a single client, so you're never
> going to destroy more than 100 per second.  That's what you need to
> parallelize.  See item 3 from
>
> 	https://urldefense.com/v3/__https://lore.kernel.org/linux-nfs/20220523154026.GD24163@fieldses.org/__;!!ACWV5N9M2RV99hQ!KK7Xqkksy2WBks12oxpw0FMQW8z7_FpSDgruhtAIrNCW5kmhvAY7noT5d6ybenxkIowyx9cVXBLDysVq$

Right! thank you for reminding me of this. I'll add it to my plate
if no one gets to it yet.

-Dai

>   
>
> Also, looks like current nfs-utils is still doing 3 commits per expiry.
>
> Steve, for some reason I think "nfsdcld: use WAL journal for faster
> commits" never got applied:
>
> 	https://urldefense.com/v3/__https://lore.kernel.org/linux-nfs/20220104222445.GF12040@fieldses.org/__;!!ACWV5N9M2RV99hQ!KK7Xqkksy2WBks12oxpw0FMQW8z7_FpSDgruhtAIrNCW5kmhvAY7noT5d6ybenxkIowyx9cVXP3Ocamj$
>
> --b.