On Thu, Sep 9, 2021 at 7:34 PM Feng Tang <feng.tang@xxxxxxxxx> wrote: > > On Thu, Sep 09, 2021 at 06:19:06PM -0700, Shakeel Butt wrote: > [...] > > > > > > I am looking into this. I was hoping we have resolution for [1] as > > > > > > these patches touch similar data structures. > > > > > > > > > > > > [1] https://lore.kernel.org/all/20210811031734.GA5193@xsang-OptiPlex-9020/T/#u > > > > > > > > > > I tried 2 debug methods for that 36.4% vm-scalability regression: > > > > > > > > > > 1. Disable the HW cache prefetcher, no effect on this case > > > > > 2. relayout and add padding to 'struct cgroup_subsys_state', reduce > > > > > the regression to 3.1% > > > > > > > > > > > > > Thanks Feng but it seems like the issue for this commit is different. > > > > Rearranging the layout didn't help. Actually the cause of slowdown is > > > > the call to queue_work() inside __mod_memcg_lruvec_state(). > > > > > > > > At the moment, queue_work() is called after 32 updates. I changed it > > > > to 128 and the slowdown of will-it-scale:page_fault[1|2|3] halved > > > > (from around 10% to 5%). I am unable to run reaim or > > > > will-it-scale:fallocate2 as I was getting weird errors. > > > > > > > > Feng, is it possible for you to run these benchmarks with the change > > > > (basically changing MEMCG_CHARGE_BATCH to 128 in the if condition > > > > before queue_work() inside __mod_memcg_lruvec_state())? > > > > > > When I checked this, I tried different changes, including this batch > > > number change :), but it didn't recover the regression (the regression > > > is slightly reduced to about 12%) > [...] > > > > Another change we can try is to remove this specific queue_work() > > altogether because this is the only significant change for the > > workload. That will give us the base performance number. If that also > > has regression then there are more issues to debug. Thanks a lot for > > your help. > > I just tested with patch removing the queue_work() in __mod_memcg_lruvec_state(), > and the regression is gone. Thanks again for confirming this. I will follow this lead and see how to improve this.
