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Date: Tue, 25 Jun 2019 10:51:45 -0700 From: Ira Weiny <ira.weiny@...el.com> To: Pingfan Liu <kernelfans@...il.com> Cc: Linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, Mike Rapoport <rppt@...ux.ibm.com>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Thomas Gleixner <tglx@...utronix.de>, John Hubbard <jhubbard@...dia.com>, "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>, Christoph Hellwig <hch@....de>, Keith Busch <keith.busch@...el.com>, Mike Kravetz <mike.kravetz@...cle.com>, Linux-kernel@...r.kernel.org Subject: Re: [PATCHv3] mm/gup: speed up check_and_migrate_cma_pages() on huge page On Tue, Jun 25, 2019 at 10:13:19PM +0800, Pingfan Liu wrote: > Both hugetlb and thp locate on the same migration type of pageblock, since > they are allocated from a free_list[]. Based on this fact, it is enough to > check on a single subpage to decide the migration type of the whole huge > page. By this way, it saves (2M/4K - 1) times loop for pmd_huge on x86, > similar on other archs. > > Furthermore, when executing isolate_huge_page(), it avoid taking global > hugetlb_lock many times, and meanless remove/add to the local link list > cma_page_list. > > Signed-off-by: Pingfan Liu <kernelfans@...il.com> > Cc: Andrew Morton <akpm@...ux-foundation.org> > Cc: Ira Weiny <ira.weiny@...el.com> > Cc: Mike Rapoport <rppt@...ux.ibm.com> > Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> > Cc: Thomas Gleixner <tglx@...utronix.de> > Cc: John Hubbard <jhubbard@...dia.com> > Cc: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com> > Cc: Christoph Hellwig <hch@....de> > Cc: Keith Busch <keith.busch@...el.com> > Cc: Mike Kravetz <mike.kravetz@...cle.com> > Cc: Linux-kernel@...r.kernel.org > --- > v2 -> v3: fix page order to size convertion > > mm/gup.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index ddde097..03cc1f4 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1342,19 +1342,22 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk, > LIST_HEAD(cma_page_list); > > check_again: > - for (i = 0; i < nr_pages; i++) { > + for (i = 0; i < nr_pages;) { > + > + struct page *head = compound_head(pages[i]); > + long step = 1; > + > + if (PageCompound(head)) > + step = 1 << compound_order(head) - (pages[i] - head); Check your precedence here. step = (1 << compound_order(head)) - (pages[i] - head); Ira > /* > * If we get a page from the CMA zone, since we are going to > * be pinning these entries, we might as well move them out > * of the CMA zone if possible. > */ > - if (is_migrate_cma_page(pages[i])) { > - > - struct page *head = compound_head(pages[i]); > - > - if (PageHuge(head)) { > + if (is_migrate_cma_page(head)) { > + if (PageHuge(head)) > isolate_huge_page(head, &cma_page_list); > - } else { > + else { > if (!PageLRU(head) && drain_allow) { > lru_add_drain_all(); > drain_allow = false; > @@ -1369,6 +1372,8 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk, > } > } > } > + > + i += step; > } > > if (!list_empty(&cma_page_list)) { > -- > 2.7.5 >
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