Messages in this thread | | | Date | Mon, 16 Feb 2015 12:50:15 +0100 | From | Vlastimil Babka <> | Subject | Re: [PATCH v2] mm: incorporate zero pages into transparent huge pages |
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On 02/11/2015 10:03 PM, Ebru Akagunduz wrote: > This patch improves THP collapse rates, by allowing zero pages. > > 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 counts pte none and mapped zero pages > with the same variable. > > The patch was tested with a program that allocates 800MB of > memory, and performs interleaved reads and writes, in a pattern > that causes some 2MB areas to first see read accesses, resulting > in the zero pfn being mapped there. > > To simulate memory fragmentation at allocation time, I modified > do_huge_pmd_anonymous_page to return VM_FAULT_FALLBACK for read > faults. > > Without the patch, only %50 of the program was collapsed into > THP and the percentage did not increase over time. > > With this patch after 10 minutes of waiting khugepaged had > collapsed %99 of the program's memory. > > Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com> > Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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