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. Thank you!
