On Tue, Feb 13, 2024 at 10:31:16PM +0800, Chengming Zhou wrote: > On 2024/2/13 06:42, Yosry Ahmed wrote: > > On Sun, Feb 11, 2024 at 5:58 AM Chengming Zhou > > <zhouchengming@xxxxxxxxxxxxx> wrote: > >> > >> All zswap entries will take a reference of zswap_pool when > >> zswap_store(), and drop it when free. Change it to use the > >> percpu_ref is better for scalability performance. > >> > >> Testing kernel build in tmpfs with memory.max=2GB > >> (zswap shrinker and writeback enabled with one 50GB swapfile). > >> > >> mm-unstable zswap-global-lru > >> real 63.20 63.12 > >> user 1061.75 1062.95 > >> sys 268.74 264.44 > > > > Are these numbers from a single run or the average of multiple runs? > > The average of 5 runs. And I just checked/compared each run result, > the improvement is stable. So yes, it should be a real performance gain. > > > It just seems that the improvement is small, and percpu refcnt is > > slightly less intuitive (and uses a bit more memory), so let's make > > sure there is a real performance gain first. > > Right, percpu_ref use a bit more memory which should be ok for our use case, > since we almost have only one zswap_pool to be using. The performance gain is > for zswap_store/load hotpath. > > > > > It would also be useful to mention how many threads/CPUs are being used here. > > My bad, the testing uses 32 threads on a 128 CPUs x86-64 machine. Thanks for the clarification. Please include such details in the commit message.
