Commit 66383800 authored Nov 21, 2020 by Matthew Wilcox (Oracle) Committed by Linus Torvalds Nov 22, 2020

mm: fix madvise WILLNEED performance problem



The calculation of the end page index was incorrect, leading to a
regression of 70% when running stress-ng.

With this fix, we instead see a performance improvement of 3%.

Fixes: e6e88712 ("mm: optimise madvise WILLNEED")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: "Chen, Rong A" <rong.a.chen@intel.com>
Link: https://lkml.kernel.org/r/20201109134851.29692-1-willy@infradead.org


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 488dac0c

mm/madvise.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -226,7 +226,7 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
		struct address_space *mapping)
		{
		XA_STATE(xas, &mapping->i_pages, linear_page_index(vma, start));
		pgoff_t end_index = end / PAGE_SIZE;
		pgoff_t end_index = linear_page_index(vma, end + PAGE_SIZE - 1);
		struct page *page;

		rcu_read_lock();

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