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.akagun...@gmail.com> > Signed-off-by: Ebru Akagunduz <ebru.akagun...@gmail.com> > Reviewed-by: Rik van Riel <r...@redhat.com> > Acked-by: Vlastimil Babka <vba...@suse.cz> > Acked-by: Zhang Yanfei <zhangyan...@cn.fujitsu.com>
Acked-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
