Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161285Ab2KOA3J (ORCPT ); Wed, 14 Nov 2012 19:29:09 -0500 Received: from mail-da0-f46.google.com ([209.85.210.46]:37536 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161112Ab2KOA3I (ORCPT ); Wed, 14 Nov 2012 19:29:08 -0500 Date: Wed, 14 Nov 2012 16:29:06 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Andrew Morton cc: "Kirill A. Shutemov" , Andrea Arcangeli , linux-mm@kvack.org, Andi Kleen , "H. Peter Anvin" , linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: Re: [PATCH v5 00/11] Introduce huge zero page In-Reply-To: <20121114133342.cc7bcd6e.akpm@linux-foundation.org> Message-ID: References: <1352300463-12627-1-git-send-email-kirill.shutemov@linux.intel.com> <20121114133342.cc7bcd6e.akpm@linux-foundation.org> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 990 Lines: 20 On Wed, 14 Nov 2012, Andrew Morton wrote: > For this reason and for general ease-of-testing: can and should we add > a knob which will enable users to disable the feature at runtime? That > way if it causes problems or if we suspect it's causing problems, we > can easily verify the theory and offer users a temporary fix. > I think it would be best to add a tunable under /sys/kernel/mm/transparent_hugepage and enable it by default whenever /sys/kernel/mm/transparent_hugepage/enabled is "always" or "madvise" and allocate the huge zero page under such circumstances. Then we can free it if disabled (or if enabled is set to "never") and avoid all the refcounting and lazy allocation that causes a regression on Kirill's benchmark. -- 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/