Re: [PATCHv4 14/17] zsmalloc: make zspage lock preemptible
From: Sergey Senozhatsky
Date: Wed Feb 12 2025 - 00:00:44 EST
On (25/02/07 21:09), Yosry Ahmed wrote:
> Can we do some perf testing to make sure this custom locking is not
> regressing performance (selfishly I'd like some zswap testing too)?
So for zsmalloc I (usually) write some simple testing code which is
triggered via sysfs (device attr) and that is completely reproducible,
so that I compares apples to apples. In this particular case I just
have a loop that creates objects (we don't need to compress or decompress
anything, zsmalloc doesn't really care)
- echo 1 > /sys/ ... / test_prepare
for (sz = 32; sz < PAGE_SIZE; sz += 64) {
for (i = 0; i < 4096; i++) {
ent->handle = zs_malloc(zram->mem_pool, sz)
list_add(ent)
}
}
And now I just `perf stat` writes:
- perf stat echo 1 > /sys/ ... / test_exec_old
list_for_each_entry
zs_map_object(ent->handle, ZS_MM_RO);
zs_unmap_object(ent->handle)
list_for_each_entry
dst = zs_map_object(ent->handle, ZS_MM_WO);
memcpy(dst, tmpbuf, ent->sz)
zs_unmap_object(ent->handle)
- perf stat echo 1 > /sys/ ... / test_exec_new
list_for_each_entry
dst = zs_obj_read_begin(ent->handle, loc);
zs_obj_read_end(ent->handle, dst);
list_for_each_entry
zs_obj_write(ent->handle, tmpbuf, ent->sz);
- echo 1 > /sys/ ... / test_finish
free all handles and ent-s
The nice part is that we don't depend on any of the upper layers, we
don't even need to compress/decompress anything; we allocate objects
of required sizes and memcpy static data there (zsmalloc doesn't have
any opinion on that) and that's pretty much it.
OLD API
=======
10 runs
369,205,778 instructions # 0.80 insn per cycle
40,467,926 branches # 113.732 M/sec
369,002,122 instructions # 0.62 insn per cycle
40,426,145 branches # 189.361 M/sec
369,051,170 instructions # 0.45 insn per cycle
40,434,677 branches # 157.574 M/sec
369,014,522 instructions # 0.63 insn per cycle
40,427,754 branches # 201.464 M/sec
369,019,179 instructions # 0.64 insn per cycle
40,429,327 branches # 198.321 M/sec
368,973,095 instructions # 0.64 insn per cycle
40,419,245 branches # 234.210 M/sec
368,950,705 instructions # 0.64 insn per cycle
40,414,305 branches # 231.460 M/sec
369,041,288 instructions # 0.46 insn per cycle
40,432,599 branches # 155.576 M/sec
368,964,080 instructions # 0.67 insn per cycle
40,417,025 branches # 245.665 M/sec
369,036,706 instructions # 0.63 insn per cycle
40,430,860 branches # 204.105 M/sec
NEW API
=======
10 runs
265,799,293 instructions # 0.51 insn per cycle
29,834,567 branches # 170.281 M/sec
265,765,970 instructions # 0.55 insn per cycle
29,829,019 branches # 161.602 M/sec
265,764,702 instructions # 0.51 insn per cycle
29,828,015 branches # 189.677 M/sec
265,836,506 instructions # 0.38 insn per cycle
29,840,650 branches # 124.237 M/sec
265,836,061 instructions # 0.36 insn per cycle
29,842,285 branches # 137.670 M/sec
265,887,080 instructions # 0.37 insn per cycle
29,852,881 branches # 126.060 M/sec
265,769,869 instructions # 0.57 insn per cycle
29,829,873 branches # 210.157 M/sec
265,803,732 instructions # 0.58 insn per cycle
29,835,391 branches # 186.940 M/sec
265,766,624 instructions # 0.58 insn per cycle
29,827,537 branches # 212.609 M/sec
265,843,597 instructions # 0.57 insn per cycle
29,843,650 branches # 171.877 M/sec
x old-api-insn
+ new-api-insn
+-------------------------------------------------------------------------------------+
|+ x|
|+ x|
|+ x|
|+ x|
|+ x|
|+ x|
|+ x|
|+ x|
|+ x|
|+ x|
|A A|
+-------------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 10 3.689507e+08 3.6920578e+08 3.6901918e+08 3.6902586e+08 71765.519
+ 10 2.657647e+08 2.6588708e+08 2.6580373e+08 2.6580734e+08 42187.024
Difference at 95.0% confidence
-1.03219e+08 +/- 55308.7
-27.9705% +/- 0.0149878%
(Student's t, pooled s = 58864.4)
> Perhaps Kairui can help with that since he was already testing this
> series.
Yeah, would be great.