From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 26 Jul 2005 17:31:26 -0700 From: Andrew Morton Subject: Re: Memory pressure handling with iSCSI Message-Id: <20050726173126.5368266b.akpm@osdl.org> In-Reply-To: <1122420376.6433.68.camel@dyn9047017102.beaverton.ibm.com> References: <1122399331.6433.29.camel@dyn9047017102.beaverton.ibm.com> <20050726111110.6b9db241.akpm@osdl.org> <1122403152.6433.39.camel@dyn9047017102.beaverton.ibm.com> <20050726114824.136d3dad.akpm@osdl.org> <20050726121250.0ba7d744.akpm@osdl.org> <1122412301.6433.54.camel@dyn9047017102.beaverton.ibm.com> <20050726142410.4ff2e56a.akpm@osdl.org> <1122414300.6433.57.camel@dyn9047017102.beaverton.ibm.com> <20050726151003.6aa3aecb.akpm@osdl.org> <1122418089.6433.62.camel@dyn9047017102.beaverton.ibm.com> <20050726160728.55245dae.akpm@osdl.org> <1122420376.6433.68.camel@dyn9047017102.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Badari Pulavarty Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: Badari Pulavarty wrote: > > On Tue, 2005-07-26 at 16:07 -0700, Andrew Morton wrote: > > Badari Pulavarty wrote: > > > > > > Here is the data with 5 ext2 filesystems. I also collected /proc/meminfo > > > every 5 seconds. As you can see, we seem to dirty 6GB of data in 20 > > > seconds of starting the test. I am not sure if its bad, since we have > > > lots of free memory.. > > > > It's bad. The logic in balance_dirty_pages() should block those write() > > callers as soon as we hit 40% dirty memory or whatever is in > > /proc/sys/vm/dirty_ratio. So something is horridly busted. > > > > Can you try reducing the number of filesystems even further? > > Single ext2 filesystem. We still dirty pretty quickly (data collected > every 5 seconds). It happens here, a bit. My machine goes up to 60% dirty when it should be clamping at 40%. The variable `total_pages' in page-writeback.c (from nr_free_pagecache_pages()) is too high. I trace it back to here: On node 0 totalpages: 1572864 DMA zone: 4096 pages, LIFO batch:1 Normal zone: 1568768 pages, LIFO batch:31 HighMem zone: 0 pages, LIFO batch:1 This machine only has 4G of memory, so the platform code is overestimating the number of pages by 50%. Can you please check your dmesg, see if your system is also getting this wrong? -- 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