From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by nf-out-0910.google.com with SMTP id c10so2189619nfd.6 for ; Thu, 09 Oct 2008 00:36:20 -0700 (PDT) Message-ID: <48EDB47E.60604@gmail.com> Date: Thu, 09 Oct 2008 09:36:30 +0200 From: Andrea Righi Reply-To: righi.andrea@gmail.com MIME-Version: 1.0 Subject: [PATCH] documentation: clarify dirty_ratio and dirty_background_ratio description (v2) References: <48EC90EC.8060306@gmail.com> <20081009105157.dd47d109.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20081009105157.dd47d109.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Randy Dunlap , Michael Kerrisk Cc: KAMEZAWA Hiroyuki , Peter Zijlstra , Andrew Morton , Michael Rubin , KOSAKI Motohiro , linux-mm@kvack.org, LKML List-ID: The current documentation of dirty_ratio and dirty_background_ratio is a bit misleading. In the documentation we say that they are "a percentage of total system memory", but the current page writeback policy, intead, is to apply the percentages to the dirtyable memory, that means free pages + reclaimable pages. Better to be more explicit to clarify this concept. Signed-off-by: Andrea Righi Signed-off-by: KAMEZAWA Hiroyuki --- Documentation/filesystems/proc.txt | 13 ++++++++----- 1 files changed, 8 insertions(+), 5 deletions(-) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 394eb2c..474bf8b 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -1380,15 +1380,18 @@ causes the kernel to prefer to reclaim dentries and inodes. dirty_background_ratio ---------------------- -Contains, as a percentage of total system memory, the number of pages at which -the pdflush background writeback daemon will start writing out dirty data. +Contains, as a percentage of the dirtyable system memory (free pages + mapped +pages + file cache, not including locked pages and HugePages), the number of +pages at which the pdflush background writeback daemon will start writing out +dirty data. dirty_ratio ----------------- -Contains, as a percentage of total system memory, the number of pages at which -a process which is generating disk writes will itself start writing out dirty -data. +Contains, as a percentage of the dirtyable system memory (free pages + mapped +pages + file cache, not including locked pages and HugePages), the number of +pages at which a process which is generating disk writes will itself start +writing out dirty data. dirty_writeback_centisecs ------------------------- -- 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