From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx189.postini.com [74.125.245.189]) by kanga.kvack.org (Postfix) with SMTP id D0D496B0081 for ; Mon, 21 May 2012 04:09:28 -0400 (EDT) Received: from /spool/local by e06smtp16.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 21 May 2012 09:09:27 +0100 Received: from d06av09.portsmouth.uk.ibm.com (d06av09.portsmouth.uk.ibm.com [9.149.37.250]) by d06nrmr1407.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q4L89Kbg1945686 for ; Mon, 21 May 2012 09:09:20 +0100 Received: from d06av09.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av09.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q4L89J4K015232 for ; Mon, 21 May 2012 02:09:19 -0600 From: ehrhardt@linux.vnet.ibm.com Subject: [PATCH 2/2] documentation: update how page-cluster affects swap I/O Date: Mon, 21 May 2012 10:09:15 +0200 Message-Id: <1337587755-4743-3-git-send-email-ehrhardt@linux.vnet.ibm.com> In-Reply-To: <1337587755-4743-1-git-send-email-ehrhardt@linux.vnet.ibm.com> References: <1337587755-4743-1-git-send-email-ehrhardt@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: axboe@kernel.dk, Christian Ehrhardt From: Christian Ehrhardt Fix of the documentation of /proc/sys/vm/page-cluster to match the behavior of the code and add some comments about what the tunable will change in that behavior. Signed-off-by: Christian Ehrhardt Acked-by: Jens Axboe --- Documentation/sysctl/vm.txt | 12 ++++++++++-- 1 files changed, 10 insertions(+), 2 deletions(-) diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 96f0ee8..4d87dc0 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -574,16 +574,24 @@ of physical RAM. See above. page-cluster -page-cluster controls the number of pages which are written to swap in -a single attempt. The swap I/O size. +page-cluster controls the number of pages up to which consecutive pages +are read in from swap in a single attempt. This is the swap counterpart +to page cache readahead. +The mentioned consecutivity is not in terms of virtual/physical addresses, +but consecutive on swap space - that means they were swapped out together. It is a logarithmic value - setting it to zero means "1 page", setting it to 1 means "2 pages", setting it to 2 means "4 pages", etc. +Zero disables swap readahead completely. The default value is three (eight pages at a time). There may be some small benefits in tuning this to a different value if your workload is swap-intensive. +Lower values mean lower latencies for initial faults, but at the same time +extra faults and I/O delays for following faults if they would have been part of +that consecutive pages readahead would have brought in. + ============================================================= panic_on_oom -- 1.7.0.4 -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org