From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 1F11D6B0044 for ; Tue, 3 Nov 2009 16:50:35 -0500 (EST) From: "Rafael J. Wysocki" Subject: Re: [PATCHv2 2/5] vmscan: Kill hibernation specific reclaim logic and unify it Date: Tue, 3 Nov 2009 22:51:53 +0100 References: <20091103002506.8869.A69D9226@jp.fujitsu.com> <200911022003.52125.rjw@sisk.pl> <20091103141200.0B3C.A69D9226@jp.fujitsu.com> In-Reply-To: <20091103141200.0B3C.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200911032251.53790.rjw@sisk.pl> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: LKML , Rik van Riel , linux-mm , Andrew Morton List-ID: On Tuesday 03 November 2009, KOSAKI Motohiro wrote: > > On Monday 02 November 2009, KOSAKI Motohiro wrote: > > > > > Then, This patch changed shrink_all_memory() to only the wrapper function of > > > > > do_try_to_free_pages(). it bring good reviewability and debuggability, and solve > > > > > above problems. > > > > > > > > > > side note: Reclaim logic unificication makes two good side effect. > > > > > - Fix recursive reclaim bug on shrink_all_memory(). > > > > > it did forgot to use PF_MEMALLOC. it mean the system be able to stuck into deadlock. > > > > > - Now, shrink_all_memory() got lockdep awareness. it bring good debuggability. > > > > > > > > As I said previously, I don't really see a reason to keep shrink_all_memory(). > > > > > > > > Do you think that removing it will result in performance degradation? > > > > > > Hmm... > > > Probably, I misunderstood your mention. I thought you suggested to kill > > > all hibernation specific reclaim code. I did. It's no performance degression. > > > (At least, I didn't observe) > > > > > > But, if you hope to kill shrink_all_memory() function itsef, the short answer is, > > > it's impossible. > > > > > > Current VM reclaim code need some preparetion to caller, and there are existing in > > > both alloc_pages_slowpath() and try_to_free_pages(). We can't omit its preparation. > > > > Well, my grepping for 'shrink_all_memory' throughout the entire kernel source > > code seems to indicate that hibernate_preallocate_memory() is the only current > > user of it. I may be wrong, but I doubt it, unless some new users have been > > added since 2.6.31. > > > > In case I'm not wrong, it should be safe to drop it from > > hibernate_preallocate_memory(), because it's there for performance reasons > > only. Now, since hibernate_preallocate_memory() appears to be the only user of > > it, it should be safe to drop it entirely. > > Hmmm... > I've try the dropping shrink_all_memory() today. but I've got bad result. > > In 3 times test, result were > > 2 times: kernel hang-up ;) > 1 time: success, but make slower than with shrink_all_memory() about 100x times. > > > Did you try to drop it yourself on your machine? Is this success? Generally, yes, but the performance was hit really badly. So, the conclusion is that we need shrink_all_memory() for things to work, which is kind of interesting. In that case, please feel free to add Acked-by: Rafael J. Wysocki to the patch. Thanks, Rafael -- 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