From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 22 Aug 2001 21:05:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 22 Aug 2001 21:04:51 -0400 Received: from humbolt.nl.linux.org ([131.211.28.48]:30987 "EHLO humbolt.nl.linux.org") by vger.kernel.org with ESMTP id ; Wed, 22 Aug 2001 21:04:31 -0400 Content-Type: text/plain; charset=US-ASCII From: Daniel Phillips To: Marcelo Tosatti Subject: Re: Memory Problem in 2.4.9 ? Date: Thu, 23 Aug 2001 03:11:09 +0200 X-Mailer: KMail [version 1.3.1] Cc: tommy@teatime.com.tw, Linux Kernel , Ben LaHaise In-Reply-To: In-Reply-To: MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Message-Id: <20010823010444Z16129-32383+926@humbolt.nl.linux.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On August 22, 2001 09:05 pm, Marcelo Tosatti wrote: > On Wed, 22 Aug 2001, Daniel Phillips wrote: > > What can we do right now? We could always just comment out the alloc failed > > message. The result will be a lot of busy waiting on dirty page writeout > > which will work but it will keep us from focussing on the question: how did > > we get so short of bounce buffers? Well, maybe we are submitting too much IO > > without intelligent throttling (/me waves at Ben). That sounds like the > > place to attack first. > > We can just wait on the writeout of lowmem buffers at page_launder() > (which will not cause IO buffering since we are doing lowmem IO, duh), and > then we are done. > > Take a look at the patch I posted before (__GFP_NOBOUNCE). A little light reading for a Wednesday afternoon ;-) Nice hack, way to go. So this will wait synchronously in try_to_free_buffers if we have to go around twice in alloc_bounce_page or alloc_bounce_bh (the latter eventually resulting in a page_alloc from kmem_cache grow). What does SLAB_LEVEL_MASK do? Did you find out by hitting the BUG when you tried the patch? Anyway, it needs a comment. I had in mind a completely different approach to try, using a semaphore to count bounce buffers, and block when they run out. Your patch fits the pattern of the current busy-waiting strategy much better. It's the right thing to do. OK, race you to the next bug ;-) -- Daniel