From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: [PATCH 4/4] writeback: Reporting dirty thresholds in /proc/vmstat Date: Sat, 21 Aug 2010 13:48:08 +0800 Message-ID: <20100821054808.GA29869@localhost> References: <1282296689-25618-1-git-send-email-mrubin@google.com> <1282296689-25618-5-git-send-email-mrubin@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Peter Zijlstra , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "jack@suse.cz" , "riel@redhat.com" , "akpm@linux-foundation.org" , "david@fromorbit.com" , "npiggin@kernel.dk" , "hch@lst.de" , "axboe@kernel.dk" To: Michael Rubin Return-path: Received: from mga11.intel.com ([192.55.52.93]:46368 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751099Ab0HUFse (ORCPT ); Sat, 21 Aug 2010 01:48:34 -0400 Content-Disposition: inline In-Reply-To: <1282296689-25618-5-git-send-email-mrubin@google.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Fri, Aug 20, 2010 at 05:31:29PM +0800, Michael Rubin wrote: > The kernel already exposes the user desired thresholds in /proc/sys/vm > with dirty_background_ratio and background_ratio. But the kernel may > alter the number requested without giving the user any indication that > is the case. > > Knowing the actual ratios the kernel is honoring can help app developers > understand how their buffered IO will be sent to the disk. > > $ grep threshold /proc/vmstat > nr_dirty_threshold 409111 > nr_dirty_background_threshold 818223 I realized that the dirty thresholds has already been exported here: $ grep Thresh /debug/bdi/8:0/stats BdiDirtyThresh: 381000 kB DirtyThresh: 1719076 kB BackgroundThresh: 859536 kB So why not use that interface directly? Thanks, Fengguang