From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 969836B0078 for ; Wed, 15 Sep 2010 17:34:20 -0400 (EDT) From: ebiederm@xmission.com (Eric W. Biederman) References: <20100914234714.8AF506EA@kernel.beaverton.ibm.com> <20100915133303.0b232671.kamezawa.hiroyu@jp.fujitsu.com> <20100915135016.C9F1.A69D9226@jp.fujitsu.com> <1284531262.27089.15725.camel@nimitz> <1284578821.27089.17409.camel@nimitz> Date: Wed, 15 Sep 2010 14:34:12 -0700 In-Reply-To: <1284578821.27089.17409.camel@nimitz> (Dave Hansen's message of "Wed, 15 Sep 2010 12:27:01 -0700") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [RFC][PATCH] update /proc/sys/vm/drop_caches documentation Sender: owner-linux-mm@kvack.org To: Dave Hansen Cc: KOSAKI Motohiro , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org, linux-mm@kvack.org, lnxninja@linux.vnet.ibm.com List-ID: Dave Hansen writes: > On Wed, 2010-09-15 at 11:37 -0700, Eric W. Biederman wrote: >> > I'm worried that there are users out there experiencing real problems >> > that aren't reporting it because "workarounds" like this just paper over >> > the issue. >> >> For what it is worth. I had a friend ask me about a system that had 50% >> of it's memory consumed by slab caches. 20GB out of 40GB. The kernel >> was suse? 2.6.27 so it's old, but if you are curious. >> /proc/sys/vm/drop_caches does nothing in that case. > > Was it the reclaimable caches doing it, though? The other really common > cause is kmalloc() leaks. It was reclaimable caches. He kept seeing the cache sizes of the problem caches shrink. On an idle system he said he was seeing about 16MB/min getting free or something like that. Something that would take hours and hours before things freed up. I asked and my friend told me that according to slabtop the slab with the most memory used kept changing dramatically and he could not see a pattern. So at least on one old kernel on one strange workload there was a problem. Eric -- 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