Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754660AbWL0Rdn (ORCPT ); Wed, 27 Dec 2006 12:33:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754657AbWL0Rdn (ORCPT ); Wed, 27 Dec 2006 12:33:43 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:58034 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964777AbWL0Rdm (ORCPT ); Wed, 27 Dec 2006 12:33:42 -0500 Date: Wed, 27 Dec 2006 18:30:13 +0100 From: Ingo Molnar To: Catalin Marinas Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH 2.6.20-rc1 00/10] Kernel memory leak detector 0.13 Message-ID: <20061227173013.GA17560@elte.hu> References: <20061216153346.18200.51408.stgit@localhost.localdomain> <20061216165738.GA5165@elte.hu> <20061217085859.GB2938@elte.hu> <20061218072932.GA5624@elte.hu> <20061227150815.GA27828@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061227150815.GA27828@elte.hu> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -5.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-5.9 required=5.9 tests=ALL_TRUSTED,BAYES_00 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1653 Lines: 34 * Ingo Molnar wrote: > > As I mentioned in a different e-mail, a way to remove the global > > hash table is to create per-cpu hashes. The only problem is that in > > these 8-10% of the cases, freeing would need to look up the other > > hashes. This would become a problem with a high number of CPUs but > > I'm not sure whether it would overtake the performance issues > > introduced by cacheline ping-ponging in the single-hash case. > > i dont think it's worth doing that. So we should either do the current > global lock & hash (bad for scalability), or a pure per-CPU design. > The pure per-CPU design would have to embedd the CPU ID the object is > attached to into the allocated object. If that is not feasible then > only the global hash remains i think. embedding the info shouldnt be /that/ hard in case of the SLAB: if the memleak info is at a negative offset from the allocated pointer. I.e. that if kmalloc() returns 'ptr', the memleak info could be at ptr-sizeof(memleak_info). That way you dont have to know the size of the object beforehand and there's absolutely no need for a global hash of any sort. (it gets a bit more complex for page aligned allocations for the buddy and for vmalloc - but that could be solved by adding one extra pointer into struct page. That is a far more preferable cost than the locking/cache overhead of a global hash.) Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/