From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752096AbXBRUxO (ORCPT ); Sun, 18 Feb 2007 15:53:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752097AbXBRUxO (ORCPT ); Sun, 18 Feb 2007 15:53:14 -0500 Received: from smtp.osdl.org ([65.172.181.24]:55960 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752096AbXBRUxN (ORCPT ); Sun, 18 Feb 2007 15:53:13 -0500 Date: Sun, 18 Feb 2007 12:53:07 -0800 From: Andrew Morton To: Miklos Szeredi Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: dirty balancing deadlock Message-Id: <20070218125307.4103c04a.akpm@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 18 Feb 2007 19:28:18 +0100 Miklos Szeredi wrote: > I was testing the new fuse shared writable mmap support, and finding > that bash-shared-mapping deadlocks (which isn't so strange ;). What > is more strange is that this is not an OOM situation at all, with > plenty of free and cached pages. > > A little more investigation shows that a similar deadlock happens > reliably with bash-shared-mapping on a loopback mount, even if only > half the total memory is used. > > The cause is slightly different in the two cases: > > - loopback mount: allocation by the underlying filesystem is stalled > on throttle_vm_writeout() > > - fuse-loop: page dirtying on the underlying filesystem is stalled on > balance_dirty_pages() > > In both cases the underlying fs is totally innocent, with no > dirty/writback pages, yet it's waiting for the global dirty+writeback > to go below the threshold, which obviously won't, until the > allocation/dirtying succeeds. > > I'm not quite sure what the solution is, and asking for thoughts. But.... these things don't just throttle. They also perform large amounts of writeback, which causes the dirty levels to subside. >>From your description it appears that this writeback isn't happening, or isn't working. How come? From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 18 Feb 2007 12:53:07 -0800 From: Andrew Morton Subject: Re: dirty balancing deadlock Message-Id: <20070218125307.4103c04a.akpm@linux-foundation.org> In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Miklos Szeredi Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Sun, 18 Feb 2007 19:28:18 +0100 Miklos Szeredi wrote: > I was testing the new fuse shared writable mmap support, and finding > that bash-shared-mapping deadlocks (which isn't so strange ;). What > is more strange is that this is not an OOM situation at all, with > plenty of free and cached pages. > > A little more investigation shows that a similar deadlock happens > reliably with bash-shared-mapping on a loopback mount, even if only > half the total memory is used. > > The cause is slightly different in the two cases: > > - loopback mount: allocation by the underlying filesystem is stalled > on throttle_vm_writeout() > > - fuse-loop: page dirtying on the underlying filesystem is stalled on > balance_dirty_pages() > > In both cases the underlying fs is totally innocent, with no > dirty/writback pages, yet it's waiting for the global dirty+writeback > to go below the threshold, which obviously won't, until the > allocation/dirtying succeeds. > > I'm not quite sure what the solution is, and asking for thoughts. But.... these things don't just throttle. They also perform large amounts of writeback, which causes the dirty levels to subside. >>From your description it appears that this writeback isn't happening, or isn't working. How come? -- 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