From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx180.postini.com [74.125.245.180]) by kanga.kvack.org (Postfix) with SMTP id 9AD816B0006 for ; Fri, 8 Mar 2013 04:40:45 -0500 (EST) Message-ID: <5139B214.3040303@symas.com> Date: Fri, 08 Mar 2013 01:40:36 -0800 From: Howard Chu MIME-Version: 1.0 Subject: Re: mmap vs fs cache References: <5136320E.8030109@symas.com> <20130307154312.GG6723@quack.suse.cz> <20130308020854.GC23767@cmpxchg.org> <5139975F.9070509@symas.com> <20130308084246.GA4411@shutemov.name> In-Reply-To: <20130308084246.GA4411@shutemov.name> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Johannes Weiner , Jan Kara , linux-kernel , linux-mm@kvack.org Kirill A. Shutemov wrote: > On Thu, Mar 07, 2013 at 11:46:39PM -0800, Howard Chu wrote: >> You're misreading the information then. slapd is doing no caching of >> its own, its RSS and SHR memory size are both the same. All it is >> using is the mmap, nothing else. The RSS == SHR == FS cache, up to >> 16GB. RSS is always == SHR, but above 16GB they grow more slowly >> than the FS cache. > > It only means, that some pages got unmapped from your process. It can > happned, for instance, due page migration. There's nothing worry about: it > will be mapped back on next page fault to the page and it's only minor > page fault since the page is in pagecache anyway. Unfortunately there *is* something to worry about. As I said already - when the test spans 30GB, the FS cache fills up the rest of RAM and the test is doing a lot of real I/O even though it shouldn't need to. Please, read the entire original post before replying. There is no way that a process that is accessing only 30GB of a mmap should be able to fill up 32GB of RAM. There's nothing else running on the machine, I've killed or suspended everything else in userland besides a couple shells running top and vmstat. When I manually drop_caches repeatedly, then eventually slapd RSS/SHR grows to 30GB and the physical I/O stops. -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/ -- 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