From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx199.postini.com [74.125.245.199]) by kanga.kvack.org (Postfix) with SMTP id 4E0E56B005D for ; Fri, 17 Aug 2012 01:31:16 -0400 (EDT) Message-ID: <502DD663.2020504@parallels.com> Date: Fri, 17 Aug 2012 09:28:03 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [RFC PATCH 1/6] memcg: pass priority to prune_icache_sb() References: <1345150430-30910-1-git-send-email-yinghan@google.com> In-Reply-To: <1345150430-30910-1-git-send-email-yinghan@google.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ying Han Cc: Michal Hocko , Johannes Weiner , Mel Gorman , KAMEZAWA Hiroyuki , Rik van Riel , Greg Thelen , Christoph Lameter , KOSAKI Motohiro , linux-mm@kvack.org On 08/17/2012 12:53 AM, Ying Han wrote: > The same patch posted two years ago at: > http://permalink.gmane.org/gmane.linux.kernel.mm/55467 > > No change since then and re-post it now mainly because it is part of the > patchset I have internally. Also, the issue that the patch addresses would > be more problematic after the patchset. > > Two changes included: > 1. only remove inode with pages in its mapping when reclaim priority hits 0. > > It helps the situation when shrink_slab() is being too agressive, it ends up > removing the inode as well as all the pages associated with the inode. > Especially when single inode has lots of pages points to it. > > The problem was observed on a production workload we run, where it has small > number of large files. Page reclaim won't blow away the inode which is pinned > by dentry which in turn is pinned by open file descriptor. But if the > application is openning and closing the fds, it has the chance to trigger > the issue. The application will experience performance hit when that happens. > > After the whole patchset, the code will call the shrinker more often by adding > shrink_slab() into target reclaim. So the performance hit will be more likely > to be observed. > > 2. avoid wrapping up when scanning inode lru. > > The target_scan_count is calculated based on the userpage lru activity, > which could be bigger than the inode lru size. avoid scanning the same > inode twice by remembering the starting point for each scan. > > Signed-off-by: Ying Han I don't doubt the problem, but having a field in sc that is used for only one shrinker, and specifically to address a corner case, sounds like a bit of a hack. Wouldn't it be possible to make sure that such inodes are in the end of the shrinkable list, so they are effectively left for last without messing with priorities? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org