Messages in this thread | | | Date | Thu, 29 Jan 2015 22:15:21 +0100 | From | Andrea Arcangeli <> | Subject | Re: [PATCH v4] mm: incorporate read-only pages into transparent huge pages |
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On Thu, Jan 29, 2015 at 04:59:07PM +0200, Ebru Akagunduz wrote: > This patch aims to improve THP collapse rates, by allowing > THP collapse in the presence of read-only ptes, like those > left in place by do_swap_page after a read fault. > > Currently THP can collapse 4kB pages into a THP when > there are up to khugepaged_max_ptes_none pte_none ptes > in a 2MB range. This patch applies the same limit for > read-only ptes. > > The patch was tested with a test program that allocates > 800MB of memory, writes to it, and then sleeps. I force > the system to swap out all but 190MB of the program by > touching other memory. Afterwards, the test program does > a mix of reads and writes to its memory, and the memory > gets swapped back in. > > Without the patch, only the memory that did not get > swapped out remained in THPs, which corresponds to 24% of > the memory of the program. The percentage did not increase > over time. > > With this patch, after 5 minutes of waiting khugepaged had > collapsed 60% of the program's memory back into THPs. > > Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com> > Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com> > Reviewed-by: Rik van Riel <riel@redhat.com> > Acked-by: Vlastimil Babka <vbabka@suse.cz> > Acked-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
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