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@xxxxxxxxx> > Reviewed-by: Rik van Riel <riel@xxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>