On Fri, Jul 5, 2024 at 7:25 PM Takero Funaki <flintglass@xxxxxxxxx> wrote: > > This patch implements proactive shrinking of zswap pool before the max > pool size limit is reached. This also changes zswap to accept new pages > while the shrinker is running. > > To prevent zswap from rejecting new pages and incurring latency when > zswap is full, this patch queues the global shrinker by a pool usage > threshold between 100% and accept_thr_percent, instead of the max pool > size. The pool size will be controlled between 90% to 91% for the > default accept_thr_percent=90. Since the current global shrinker > continues to shrink until accept_thr_percent, we do not need to maintain > the hysteresis variable tracking the pool limit overage in > zswap_store(). > > Before this patch, zswap rejected pages while the shrinker is running > without incrementing zswap_pool_limit_hit counter. It could be a reason > why zswap writethrough new pages before writeback old pages. With this > patch, zswap accepts new pages while shrinking, and zswap increments > the counter when and only when zswap rejects pages by the max pool size. > > Now, reclaims smaller than the proactive shrinking amount finish > instantly and trigger background shrinking. Admins can check if new > pages are buffered by zswap by monitoring the pool_limit_hit counter. > > The name of sysfs tunable accept_thr_percent is unchanged as it is still > the stop condition of the shrinker. > The respective documentation is updated to describe the new behavior. > > Signed-off-by: Takero Funaki <flintglass@xxxxxxxxx> Code-wise and idea-wise, I like this patch :) This is dependent on other changes (as you have pointed out), but if the series goes through, please feel free to include: Reviewed-by: Nhat Pham <nphamcs@xxxxxxxxx>
