From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: [RFC 2/2] x86_64: expand kernel stack to 16K Date: Wed, 28 May 2014 11:27:17 +0200 Message-ID: <20140528092717.GA17220@pd.tnic> References: <1401260039-18189-1-git-send-email-minchan@kernel.org> <1401260039-18189-2-git-send-email-minchan@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <1401260039-18189-2-git-send-email-minchan@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Minchan Kim Cc: linux-kernel@vger.kernel.org, Andrew Morton , linux-mm@kvack.org, "H. Peter Anvin" , Ingo Molnar , Peter Zijlstra , Mel Gorman , Rik van Riel , Johannes Weiner , Hugh Dickins , rusty@rustcorp.com.au, mst@redhat.com, Dave Hansen , Steven Rostedt List-Id: linux-mm.kvack.org On Wed, May 28, 2014 at 03:53:59PM +0900, Minchan Kim wrote: > While I play inhouse patches with much memory pressure on qemu-kvm, > 3.14 kernel was randomly crashed. The reason was kernel stack overflow. > > When I investigated the problem, the callstack was a little bit deeper > by involve with reclaim functions but not direct reclaim path. > > I tried to diet stack size of some functions related with alloc/reclaim > so did a hundred of byte but overflow was't disappeard so that I encounter > overflow by another deeper callstack on reclaim/allocator path. > > Of course, we might sweep every sites we have found for reducing > stack usage but I'm not sure how long it saves the world(surely, > lots of developer start to add nice features which will use stack > agains) and if we consider another more complex feature in I/O layer > and/or reclaim path, it might be better to increase stack size( > meanwhile, stack usage on 64bit machine was doubled compared to 32bit > while it have sticked to 8K. Hmm, it's not a fair to me and arm64 > already expaned to 16K. ) Hmm, stupid question: what happens when 16K is not enough too, do we increase again? When do we stop increasing? 1M, 2M... ? Sounds like we want to make it a config option with a couple of sizes for everyone to be happy. :-) -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --