On Tue, Apr 02, 2013 at 10:24:22AM +0900, Minchan Kim wrote: > Hi Shaohua, > > On Mon, Apr 01, 2013 at 09:26:05PM +0800, Shaohua Li wrote: > > In page reclaim, huge page is split. split_huge_page() adds tail pages to LRU > > list. Since we are reclaiming a huge page, it's better we reclaim all subpages > > of the huge page instead of just the head page. This patch adds split tail > > pages to shrink page list so the tail pages can be reclaimed soon. > > > > Before this patch, run a swap workload: > > thp_fault_alloc 3492 > > thp_fault_fallback 608 > > thp_collapse_alloc 6 > > thp_collapse_alloc_failed 0 > > thp_split 916 > > > > With this patch: > > thp_fault_alloc 4085 > > thp_fault_fallback 16 > > thp_collapse_alloc 90 > > thp_collapse_alloc_failed 0 > > thp_split 1272 > > > > fallback allocation is reduced a lot. > > What I have a concern is that there is about spatial locality about 2M all pages > expecially, THP-always case. But yes, THP already have done it via > lru_add_page_tail and yours makes more sense if we really intended it. > > But I didn't like passing page_list to split_huge_page, either. > Couldn't we do it in isolate_lru_pages in shrink_inactive_list? > Maybe, we can add new isolate_mode, ISOLATE_SPLIT_HUGEPAGE. > One problem I can see is deadlock of zone->lru_lock so maybe we have to > release the lock the work and re-hold it. I'd prefer split huge page after page_check_references like what we do now. It's possible we don't want to reclaim (so split) the page at all. Thanks, Shaohua -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>