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Date: Fri, 28 Jun 2019 11:59:29 +0800 From: Pingfan Liu <kernelfans@...il.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Linux-mm@...ck.org, Ira Weiny <ira.weiny@...el.com>, 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>, LKML <Linux-kernel@...r.kernel.org> Subject: Re: [PATCHv5] mm/gup: speed up check_and_migrate_cma_pages() on huge page On Fri, Jun 28, 2019 at 7:25 AM Andrew Morton <akpm@...ux-foundation.org> wrote: > > On Thu, 27 Jun 2019 13:15:45 +0800 Pingfan Liu <kernelfans@...il.com> 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. > > > > Thanks, looks good to me. Have any timing measurements been taken? Not yet. It is a little hard to force huge page to be allocated CMA area. Should I provide the measurements? > > > ... > > > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -1336,25 +1336,30 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk, > > struct vm_area_struct **vmas, > > unsigned int gup_flags) > > { > > - long i; > > + long i, step; > > I'll make these variables unsigned long - to match nr_pages and because > we have no need for them to be negative. OK, will fix it. Thanks, Pingfan > > > ...
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