2020년 3월 24일 (화) 오전 2:43, Johannes Weiner <hannes@xxxxxxxxxxx>님이 작성: > > On Mon, Mar 23, 2020 at 02:52:12PM +0900, js1304@xxxxxxxxx wrote: > > From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > > > reclaim_stat's rotate is used for controlling the ratio of scanning page > > between file and anonymous LRU. All new anonymous pages are counted > > for rotate before the patch, protecting anonymous pages on active LRU, and, > > it makes that reclaim on anonymous LRU is less happened than file LRU. > > > > Now, situation is changed. all new anonymous pages are not added > > to the active LRU so rotate would be far less than before. It will cause > > that reclaim on anonymous LRU happens more and it would result in bad > > effect on some system that is optimized for previous setting. > > > > Therefore, this patch counts a new anonymous page as a reclaim_state's > > rotate. Although it is non-logical to add this count to > > the reclaim_state's rotate in current algorithm, reducing the regression > > would be more important. > > > > I found this regression on kernel-build test and it is roughly 2~5% > > performance degradation. With this workaround, performance is completely > > restored. > > > > v2: fix a bug that reuses the rotate value for previous page > > I agree with the rationale, but the magic bit in the page->lru list > pointers seems pretty ugly. Yes, pretty ugly. > I wrote a patch a few years ago that split lru_add_pvecs into an add > and a putback component. This was to avoid unintentional balancing > effects of LRU isolations, but I think you can benefit from that > cleanup here as well. Would you mind taking a look at it and maybe > take it up into your series? > > https://lore.kernel.org/patchwork/patch/685708/ Thanks for pointing that. I will remove the magic bit and imitate your patch to solve the problem of this patch. Thanks.
