On Thu, Jun 6, 2024 at 5:53 PM Takero Funaki <flintglass@xxxxxxxxx> wrote: > > This patch limits the number of zpools used by zswap on smaller systems. > > Currently, zswap allocates 32 pools unconditionally. This was > implemented to reduce contention on per-zpool locks. However, it incurs > allocation overhead by distributing pages across pools, wasting memory > on systems with fewer CPUs and less RAM. > > This patch allocates approximately 2*CPU zpools, with a minimum of 1 > zpool for single-CPU systems and up to 32 zpools for systems with 16 or > more CPUs. This number is sufficient to keep the probability of > busy-waiting by a thread under 40%. The upper limit of 32 zpools remains > unchanged. > > For memory, it limits to 1 zpool per 60MB of memory for the 20% default > max pool size limit, assuming the best case with no fragmentation in > zspages. It expects 90% pool usage for zsmalloc. > > Signed-off-by: Takero Funaki <flintglass@xxxxxxxxx> > --- I think this needs benchmarking. Theoretical justification is nice, but I'm not convinced it'll translate neatly to the messy world of real life systems.
