On Fri, Apr 09, 2021 at 09:50:45AM -0700, Shakeel Butt wrote:
> On Fri, Apr 9, 2021 at 9:35 AM Masayoshi Mizuma <msys.mizuma@xxxxxxxxx> wrote:
> >
> [...]
> > > Can you please explain how to read these numbers? Or at least put a %
> > > regression.
> >
> > Let me summarize them here.
> > The total duration ('total' column above) of each system call is as follows
> > if v5.8 is assumed as 100%:
> >
> > - sendto:
> > - v5.8 100%
> > - v5.9 128%
> > - v5.12-rc6 116%
> >
> > - revfrom:
> > - v5.8 100%
> > - v5.9 114%
> > - v5.12-rc6 108%
> >
>
> Thanks, that is helpful. Most probably the improvement of 5.12 from
> 5.9 is due to 3de7d4f25a7438f ("mm: memcg/slab: optimize objcg stock
> draining").
>
> [...]
> > >
> > > One idea would be to increase MEMCG_CHARGE_BATCH.
> >
> > Thank you for the idea! It's hard-corded as 32 now, so I'm wondering it may be
> > a good idea to make MEMCG_CHARGE_BATCH tunable from a kernel parameter or something.
> >
>
Hi!
Thank you for your comments!
> Can you rerun the benchmark with MEMCG_CHARGE_BATCH equal 64UL?
Yes, I reran the benchmark with MEMCG_CHARGE_BATCH == 64UL, but it seems that
it doesn't reduce the duration of system calls...
- v5.12-rc6 vanilla
syscall total
(msec)
--------- --------
sendto 3049.221
recvfrom 2421.601
- v5.12-rc6 with MEMCG_CHARGE_BATCH==64
syscall total
(msec)
--------- --------
sendto 3071.607
recvfrom 2436.488
> I think with memcg stats moving to rstat, the stat accuracy is not an
> issue if we increase MEMCG_CHARGE_BATCH to 64UL. Not sure if we want
> this to be tuneable but most probably we do want this to be sync'ed
> with SWAP_CLUSTER_MAX.
Thanks. I understand that.
Waiman posted some patches to reduce the overhead [1]. I'll try the patch.
[1]: https://lore.kernel.org/linux-mm/51ea6b09-b7ee-36e9-a500-b7141bd3a42b@xxxxxxxxxx/T/#me75806a3555e7a42e793f099b98c42e687962d10
Thanks!
Masa
