Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752481AbbBXISV (ORCPT ); Tue, 24 Feb 2015 03:18:21 -0500 Received: from lgeamrelo04.lge.com ([156.147.1.127]:54210 "EHLO lgeamrelo04.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751090AbbBXISR (ORCPT ); Tue, 24 Feb 2015 03:18:17 -0500 X-Original-SENDERIP: 10.177.222.143 X-Original-MAILFROM: minchan@kernel.org From: Minchan Kim To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Rik van Riel , Michal Hocko , Johannes Weiner , Mel Gorman , Shaohua Li , Yalin.Wang@sonymobile.com, Minchan Kim Subject: [PATCH RFC 1/4] mm: throttle MADV_FREE Date: Tue, 24 Feb 2015 17:18:14 +0900 Message-Id: <1424765897-27377-1-git-send-email-minchan@kernel.org> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2245 Lines: 66 Recently, Shaohua reported that MADV_FREE is much slower than MADV_DONTNEED in his MADV_FREE bomb test. The reason is many of applications went to stall with direct reclaim since kswapd's reclaim speed isn't fast than applications's allocation speed so that it causes lots of stall and lock contention. This patch throttles MADV_FREEing so it works only if there are enough pages in the system which will not trigger backgroud/ direct reclaim. Otherwise, MADV_FREE falls back to MADV_DONTNEED because there is no point to delay freeing if we know system is under memory pressure. When I test the patch on my 3G machine + 12 CPU + 8G swap, test: 12 processes loop = 5; mmap(512M); while (loop--) { memset(512M); madvise(MADV_FREE or MADV_DONTNEED); } 1) dontneed: 6.78user 234.09system 0:48.89elapsed 2) madvfree: 6.03user 401.17system 1:30.67elapsed 3) madvfree + this ptach: 5.68user 113.42system 0:36.52elapsed It's clearly win. Reported-by: Shaohua Li Signed-off-by: Minchan Kim --- mm/madvise.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 6d0fcb8921c2..81bb26ecf064 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -523,8 +523,17 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, * XXX: In this implementation, MADV_FREE works like * MADV_DONTNEED on swapless system or full swap. */ - if (get_nr_swap_pages() > 0) - return madvise_free(vma, prev, start, end); + if (get_nr_swap_pages() > 0) { + unsigned long threshold; + /* + * If we have trobule with memory pressure(ie, + * under high watermark), free pages instantly. + */ + threshold = min_free_kbytes >> (PAGE_SHIFT - 10); + threshold = threshold + (threshold >> 1); + if (nr_free_pages() > threshold) + return madvise_free(vma, prev, start, end); + } /* passthrough */ case MADV_DONTNEED: return madvise_dontneed(vma, prev, start, end); -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/