From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754586Ab0IOVeU (ORCPT ); Wed, 15 Sep 2010 17:34:20 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:41233 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753455Ab0IOVeT (ORCPT ); Wed, 15 Sep 2010 17:34:19 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Dave Hansen Cc: KOSAKI Motohiro , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org, linux-mm@kvack.org, lnxninja@linux.vnet.ibm.com 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: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-XM-SPF: eid=;;;mid=;;;hst=in01.mta.xmission.com;;;ip=98.207.157.188;;;frm=ebiederm@xmission.com;;;spf=neutral X-SA-Exim-Connect-IP: 98.207.157.188 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 1.5 TR_Symld_Words too many words that have symbols inside * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.5 XM_Body_Dirty_Words Contains a dirty word * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.4 UNTRUSTED_Relay Comes from a non-trusted relay X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Dave Hansen X-Spam-Relay-Country: Subject: Re: [RFC][PATCH] update /proc/sys/vm/drop_caches documentation X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Fri, 06 Aug 2010 16:31:04 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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