mm/gup: decrement head page once for group of subpages
mainline inclusion from mainline-5.13-rc1 commit 31b912de category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I408MI CVE: NA ------------------------------------------------- Rather than decrementing the head page refcount one by one, we walk the page array and checking which belong to the same compound_head. Later on we decrement the calculated amount of references in a single write to the head page. To that end switch to for_each_compound_head() does most of the work. set_page_dirty() needs no adjustment as it's a nop for non-dirty head pages and it doesn't operate on tail pages. This considerably improves unpinning of pages with THP and hugetlbfs: - THP gup_test -t -m 16384 -r 10 [-L|-a] -S -n 512 -w PIN_LONGTERM_BENCHMARK (put values): ~87.6k us -> ~23.2k us - 16G with 1G huge page size gup_test -f /mnt/huge/file -m 16384 -r 10 [-L|-a] -S -n 512 -w PIN_LONGTERM_BENCHMARK: (put values): ~87.6k us -> ~27.5k us Link: https://lkml.kernel.org/r/20210212130843.13865-3-joao.m.martins@oracle.comSigned-off-by: NJoao Martins <joao.m.martins@oracle.com> Reviewed-by: NJohn Hubbard <jhubbard@nvidia.com> Reviewed-by: NJason Gunthorpe <jgg@nvidia.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Doug Ledford <dledford@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org> Signed-off-by: NChengyang Fan <cy.fan@huawei.com> Reviewed-by: NChen Wandun <chenwandun@huawei.com> Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
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