On 4/12/21 3:05 PM, Roman Gushchin wrote:
On Fri, Apr 09, 2021 at 07:18:37PM -0400, Waiman Long wrote:
With the recent introduction of the new slab memory controller, we
eliminate the need for having separate kmemcaches for each memory
cgroup and reduce overall kernel memory usage. However, we also add
additional memory accounting overhead to each call of kmem_cache_alloc()
and kmem_cache_free().
For workloads that require a lot of kmemcache allocations and
de-allocations, they may experience performance regression as illustrated
in [1].
With a simple kernel module that performs repeated loop of 100,000,000
kmem_cache_alloc() and kmem_cache_free() of 64-byte object at module
init. The execution time to load the kernel module with and without
memory accounting were:
with accounting = 6.798s
w/o accounting = 1.758s
That is an increase of 5.04s (287%). With this patchset applied, the
execution time became 4.254s. So the memory accounting overhead is now
2.496s which is a 50% reduction.
Btw, there were two recent independent report about benchmark results
regression caused by the introduction of the per-object accounting:
1) Xing reported a hackbench regression:
https://lkml.org/lkml/2021/1/13/1277
2) Masayoshi reported a pgbench regression:
https://www.spinics.net/lists/linux-mm/msg252540.html
I wonder if you can run them (or at least one) and attach the result
to the series? It would be very helpful.
Actually, it was a bug reported filed by Masayoshi-san that triggered me
to work on reducing the memory accounting overhead. He is also in the cc
line and so is aware of that. I will cc Xing in my v2 patch.
Cheers,
Longman
