From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <46B23666.3020205@redhat.com> Date: Thu, 02 Aug 2007 15:54:14 -0400 From: Chuck Ebbert MIME-Version: 1.0 Subject: Re: [PATCH] balance_dirty_pages - exit loop when no more pages available References: <1185901890.3133.33.camel@castor.rsk.org> In-Reply-To: <1185901890.3133.33.camel@castor.rsk.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Peter Zijlstra Cc: richard kennedy , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On 07/31/2007 01:11 PM, richard kennedy wrote: Peter, did you see this? > exit loop in balance_dirty_pages when no more pages available to write > > On a bdi that has very little traffic balance_dirty_pages can loop > needlessly waiting until do_writepages has written enough pages. > > do_writepages will return encountered_congestion==0 && nr_to_write > 0 > when it has completed a pass but did not find enough pages available to > write. balance_dirty_pages ignores this and keeps looping until a total > of chunk pages was written. > > this patch adds an extra exit condition to break out of the loop in this > case. > > I've tested this on my amd64 desktop, and I also have a version of this > patch that includes a printk and a test case that occasionally does > trigger this condition. > > Signed-off-by: Richard Kennedy > > ------ > --- linux-2.6.22.1/mm/page-writeback.c.orig 2007-07-30 16:36:09.000000000 +0100 > +++ linux-2.6.22.1/mm/page-writeback.c 2007-07-31 16:26:43.000000000 +0100 > @@ -250,6 +250,8 @@ static void balance_dirty_pages(struct a > pages_written += write_chunk - wbc.nr_to_write; > if (pages_written >= write_chunk) > break; /* We've done our duty */ > + if (!wbc.encountered_congestion && wbc.nr_to_write > 0) > + break; /* didn't find enough to do */ > } > congestion_wait(WRITE, HZ/10); > } > -- 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