From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id BE5F76B004D for ; Fri, 7 Aug 2009 10:36:07 -0400 (EDT) Subject: Re: [RFC][PATCH] mm: stop balance_dirty_pages doing too much work From: Richard Kennedy In-Reply-To: <1249647601.32113.700.camel@twins> References: <1245839904.3210.85.camel@localhost.localdomain> <1249647601.32113.700.camel@twins> Content-Type: text/plain Date: Fri, 07 Aug 2009 15:36:01 +0100 Message-Id: <1249655761.2719.11.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Peter Zijlstra Cc: Andrew Morton , linux-mm , lkml , Chris Mason List-ID: On Fri, 2009-08-07 at 14:20 +0200, Peter Zijlstra wrote: > On Wed, 2009-06-24 at 11:38 +0100, Richard Kennedy wrote: ... > OK, so Chris ran into this bit yesterday, complaining that he'd only get > very few write requests and couldn't saturate his IO channel. > > Now, since writing out everything once there's something to do sucks for > Richard, but only writing out stuff when we're over the limit sucks for > Chris (since we can only be over the limit a little), the best thing > would be to only write out when we're over the background limit. Since > that is the low watermark we use for throttling it makes sense that we > try to write out when above that. > > However, since there's a lack of bdi_background_thresh, and I don't > think introducing one just for this is really justified. How about the > below? > > Chris how did this work for you? Richard, does this make things suck for > you again? > > --- > mm/page-writeback.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 81627eb..92f42d6 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -545,7 +545,7 @@ static void balance_dirty_pages(struct address_space *mapping) > * threshold otherwise wait until the disk writes catch > * up. > */ > - if (bdi_nr_reclaimable > bdi_thresh) { > + if (bdi_nr_reclaimable > bdi_thresh/2) { > writeback_inodes(&wbc); > pages_written += write_chunk - wbc.nr_to_write; > get_dirty_limits(&background_thresh, &dirty_thresh, > > I'll run some tests and let you know :) But what if someone has changed the vm settings? Maybe something like (bdi_thresh * dirty_background_ratio / dirty_ratio) might be better ? Chris, what sort of workload are you having problems with? regards Richard -- 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