On Mon, Mar 03, 2025 at 12:47:22AM -0800, Kanchana P Sridhar wrote: > This patch modifies the acomp_ctx resources' lifetime to be from pool > creation to deletion. A "bool __online" and "u8 nr_reqs" are added to > "struct crypto_acomp_ctx" which simplify a few things: > > 1) zswap_pool_create() will initialize all members of each percpu acomp_ctx > to 0 or NULL and only then initialize the mutex. > 2) CPU hotplug will set nr_reqs to 1, allocate resources and set __online > to true, without locking the mutex. > 3) CPU hotunplug will lock the mutex before setting __online to false. It > will not delete any resources. > 4) acomp_ctx_get_cpu_lock() will lock the mutex, then check if __online > is true, and if so, return the mutex for use in zswap compress and > decompress ops. > 5) CPU onlining after offlining will simply check if either __online or > nr_reqs are non-0, and return 0 if so, without re-allocating the > resources. > 6) zswap_pool_destroy() will call a newly added zswap_cpu_comp_dealloc() to > delete the acomp_ctx resources. > 7) Common resource deletion code in case of zswap_cpu_comp_prepare() > errors, and for use in zswap_cpu_comp_dealloc(), is factored into a new > acomp_ctx_dealloc(). > > The CPU hot[un]plug callback functions are moved to "pool functions" > accordingly. > > The per-cpu memory cost of not deleting the acomp_ctx resources upon CPU > offlining, and only deleting them when the pool is destroyed, is as follows: > > IAA with batching: 64.8 KB > Software compressors: 8.2 KB I am assuming this is specifically on x86_64, so let's call that out.
