Re: [PATCH 00/13] mm, swap: rework of swap allocator locks

[Kairui Song]

On Wed, Oct 23, 2024 at 6:27 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, 23 Oct 2024 03:24:38 +0800 Kairui Song <ryncsn@xxxxxxxxx> wrote:
>
> > After this series, lock contention on si->lock is nearly unobservable
> > with `perf lock` with the same test above :
> >
> >   contended   total wait     max wait     avg wait         type   caller
> >   ... snip ...
> >          91    204.62 us      4.51 us      2.25 us     spinlock   cluster_move+0x2e
> >   ... snip ...
> >          47    125.62 us      4.47 us      2.67 us     spinlock   cluster_move+0x2e
> >   ... snip ...
> >          23     63.15 us      3.95 us      2.74 us     spinlock   cluster_move+0x2e
> >   ... snip ...
> >          17     41.26 us      4.58 us      2.43 us     spinlock   cluster_isolate_lock+0x1d
> >   ... snip ...
>
> Were any overall runtime benefits observed?

Yes, see the "Tests" results in the cover letter (summary: up to 50%
build time saved for build linux kernel test when under pressure, with
either mTHP or 4K pages):

time make -j96 / 768M memcg, 4K pages, 10G ZRAM, on Intel 8255C * 2 in VM:
(avg of 4 test run)
Before:
Sys time: 73578.30, Real time: 864.05
After: (-54.7% sys time, -49.3% real time)
Sys time: 33314.76, Real time: 437.67

time make -j96 / 1152M memcg, 64K mTHP, 10G ZRAM, on Intel 8255C * 2 in VM:
(avg of 4 test run)
Before:
Sys time: 74044.85, Real time: 846.51
After: (-51.4% sys time, -47.7% real time, -63.2% mTHP failure)
Sys time: 35958.87, Real time: 442.69

Tests on the host bare metal showed similar results.

There are some other test results I didn't include in the cover letter
for V1 yet and I'm still testing more scenarios, eg. mysql test in 1G
memcg and with 96 workers and ZRAM swap:
before:
    transactions:                        755630 (6292.11 per sec.)
    queries:                             12090080 (100673.69 per sec.)
after:
    transactions:                        1077156 (8972.73 per sec.)
    queries:                             17234496 (143563.65 per sec.)

~30% faster.

Also the mTHP swap allocation success rate is higher, I can highlight
these changes in V2.