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 5ED626B006A for ; Fri, 22 Jan 2010 15:58:27 -0500 (EST) From: "Rafael J. Wysocki" Subject: Re: [RFC][PATCH] PM: Force GFP_NOIO during suspend/resume (was: Re: [linux-pm] Memory allocations in .suspend became very unreliable) Date: Fri, 22 Jan 2010 21:58:46 +0100 References: <20100121091023.3775.A69D9226@jp.fujitsu.com> <201001212121.50272.rjw@sisk.pl> <20100122100155.6C03.A69D9226@jp.fujitsu.com> In-Reply-To: <20100122100155.6C03.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201001222158.46337.rjw@sisk.pl> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Benjamin Herrenschmidt , Maxim Levitsky , linux-pm@lists.linux-foundation.org, LKML , linux-mm , Andrew Morton List-ID: On Friday 22 January 2010, KOSAKI Motohiro wrote: > > > Probably we have multiple option. but I don't think GFP_NOIO is good > > > option. It assume the system have lots non-dirty cache memory and it isn't > > > guranteed. > > > > Basically nothing is guaranteed in this case. However, does it actually make > > things _worse_? > > Hmm.. > Do you mean we don't need to prevent accidental suspend failure? > Perhaps, I did misunderstand your intention. If you think your patch solve > this this issue, I still disagree. No, I don't. > but If you think your patch mitigate the pain of this issue, I agree it. That's what I wanted to say really. > I don't have any reason to oppose your first patch. Great! > > What _exactly_ does happen without the $subject patch if the > > system doesn't have non-dirty cache memory and someone makes a GFP_KERNEL > > allocation during suspend? > > Page allocator prefer to spent lots time for reclaimable memory searching than > returning NULL. IOW, it can spent time few second if it doesn't have > reclaimable memory. > In typical case, OOM killer forcely make enough free memory if the system > don't have any memory. But under suspending time, oom killer is disabled. > So, if the caller (probably drivers) call alloc >1000times, the system > spent lots seconds. > > In this case, GFP_NOIO doesn't help. slowness behavior is caused by > freeable memory search, not slow i/o. > > However, if strange i/o device makes any i/o slowness, GFP_NOIO might help. > In this case, please don't ask me about i/o thing. I don't know ;) OK, thanks for the explanation. 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