From mboxrd@z Thu Jan 1 00:00:00 1970 From: KOSAKI Motohiro Subject: Re: [PATCH] mm: do not print backtraces on GFP_ATOMIC failures Date: Mon, 27 Sep 2010 11:17:19 +0900 (JST) Message-ID: <20100927110723.6B37.A69D9226@jp.fujitsu.com> References: <20100921094638.9910add0.akpm@linux-foundation.org> <1285088427.2617.723.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:54726 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757773Ab0I0CRW (ORCPT ); Sun, 26 Sep 2010 22:17:22 -0400 In-Reply-To: <1285088427.2617.723.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: > > > @@ -72,7 +72,7 @@ struct vm_area_struct; > > > /* This equals 0, but use constants in case they ever change */ > > > #define GFP_NOWAIT (GFP_ATOMIC & ~__GFP_HIGH) > > > /* GFP_ATOMIC means both !wait (__GFP_WAIT not set) and use emergency pool */ > > > -#define GFP_ATOMIC (__GFP_HIGH) > > > +#define GFP_ATOMIC (__GFP_HIGH | __GFP_NOWARN) > > > #define GFP_NOIO (__GFP_WAIT) > > > #define GFP_NOFS (__GFP_WAIT | __GFP_IO) > > > #define GFP_KERNEL (__GFP_WAIT | __GFP_IO | __GFP_FS) > > > > A much finer-tuned implementation would be to add __GFP_NOWARN just to > > the networking call sites. I asked about this in June and it got > > nixed: > > > > http://www.spinics.net/lists/netdev/msg131965.html > > -- > > Yes, I remember this particular report was useful to find and correct a > bug. > > I dont know what to say. > > Being silent or verbose, it really depends on the context ? At least, MM developers don't want to track network allocation failure issue. We don't have enough knowledge in this area. To be honest, We are unhappy current bad S/N bug report rate ;) Traditionally, We hoped this warnings help to debug VM issue. but It haven't happen. We haven't detect VM issue from this allocation failure report. Instead, We've received a lot of network allocation failure report. Recently, The S/N ratio became more bad. If the network device enable jumbo frame feature, order-2 GFP_ATOMIC allocation is called frequently. Anybody don't have to assume order-2 allocation can success anytime. I'm not against accurate warning at all. but I cant tolerate this semi-random warning steal our time. If anyone will not make accurate warning, I hope to remove this one completely instead.