On Sat, 16 Oct 2021 10:28:54 +0800 Zhaoyang Huang <huangzhaoyang@xxxxxxxxx> wrote: > On Sat, Oct 16, 2021 at 4:00 AM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > On Fri, 15 Oct 2021 14:15:29 +0800 Huangzhaoyang <huangzhaoyang@xxxxxxxxx> wrote: > > > > > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > > > > > Sibling thread of the same process could refault the reclaimed pages > > > in the same time, which would be typical in None global reclaim and > > > introduce thrashing. > > > > "None" -> "node", I assume? > > > > > --- a/mm/vmscan.c > > > +++ b/mm/vmscan.c > > > @@ -2841,6 +2841,11 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) > > > sc->memcg_low_skipped = 1; > > > continue; > > > } > > > + /* > > > + * Don't bother current when its memcg is below low > > > + */ > > > > The comment explains what the code is doing, but the code itself > > already does this. Please can we have a comment that explains *why* > > the code is doing this? > We find that the patch help direct reclaiming bail out early and > eliminate page thrashing for some scenarios(etc APP start on android). > The case could be worse if each APP possess a unique memcg(pages on > current's lru are reclaimed more than global reclaim) What I meant was: please redo the patch with a comment which explains "why the code does this", rather than "what the code does". Also, as this is a performance enhancement, it is preferred to have some performance testing results in the changelog.
