From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759646AbYBFTxh (ORCPT ); Wed, 6 Feb 2008 14:53:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755534AbYBFTx3 (ORCPT ); Wed, 6 Feb 2008 14:53:29 -0500 Received: from terminus.zytor.com ([198.137.202.10]:58852 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755040AbYBFTx2 (ORCPT ); Wed, 6 Feb 2008 14:53:28 -0500 Message-ID: <47AA102F.1070105@zytor.com> Date: Wed, 06 Feb 2008 11:53:19 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Hugh Dickins CC: Tomasz Chmielewski , LKML , Mika Lawando Subject: Re: What is the limit size of tmpfs /dev/shm ? References: <47A9CA0E.3030507@wpkg.org> <47AA0A2E.30701@zytor.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hugh Dickins wrote: > > In theory, yes, and should be true in practice before it hits swap. > But I think you'll find our swap handling is too primitive for tmpfs > to perform well once we hit swap. Most filesystems pay considerable > attention to good performance within their constraints of correctness. > Whereas with tmpfs we've just never worried about the performance once > swapping. It's used so you don't lose your data, but if you're really > expecting to be going to disk very much, better start with a filesystem > really designed for that. > That sounds like a problem in our overall swap handling, not specifically in tmpfs. Now, I can't say anything concrete about heavy swap conditions, but in light swap conditions I have measured a 20x performance improvement(!) over ext3 on real workloads. -hpa