From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 6A7776B0088 for ; Thu, 28 May 2009 03:02:41 -0400 (EDT) Date: Thu, 28 May 2009 00:00:47 -0700 From: "Larry H." Subject: Re: [patch 0/5] Support for sanitization flag in low-level page allocator Message-ID: <20090528070047.GC29711@oblivion.subreption.com> References: <20090520183045.GB10547@oblivion.subreption.com> <4A15A8C7.2030505@redhat.com> <20090522073436.GA3612@elte.hu> <20090522113809.GB13971@oblivion.subreption.com> <20090523124944.GA23042@elte.hu> <4A187BDE.5070601@redhat.com> <20090527223421.GA9503@elte.hu> <20090528072702.796622b6@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090528072702.796622b6@lxorguk.ukuu.org.uk> Sender: owner-linux-mm@kvack.org To: Alan Cox Cc: Ingo Molnar , Rik van Riel , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Ingo Molnar , pageexec@freemail.hu List-ID: On 07:27 Thu 28 May , Alan Cox wrote: > > > As for being swapped out - I do not believe that kernel stacks can > > > ever be swapped out in Linux. > > > > yes, i referred to that as an undesirable option - because it slows > > down pthread_create() quite substantially. > > > > This needs before/after pthread_create() benchmark results. > > kernel stacks can end up places you don't expect on hypervisor based > systems. > > In most respects the benchmarks are pretty irrelevant - wiping stuff has > a performance cost, but its the sort of thing you only want to do when > you have a security requirement that needs it. At that point the > performance is secondary. > > Alan Right, besides I believe Ingo is confused about the nature of the patch. It looks like he believes it's about userland memory sanitization, when that isn't what is being done here. If he still believe this has anything to do with it directly, or can introduce a performance impact on pthread_create() (remember we are sanitizing on release only...), I'll be pleased to provide benchmark results that prove it wrong (or right, if it was the case). Any existent benchmark tests available that I can modify to suit our needs here, or I'll need to waste some time on writing them from scratch? Larry -- 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