Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261396AbVCRAF0 (ORCPT ); Thu, 17 Mar 2005 19:05:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261390AbVCRAFZ (ORCPT ); Thu, 17 Mar 2005 19:05:25 -0500 Received: from omx3-ext.sgi.com ([192.48.171.20]:16038 "EHLO omx3.sgi.com") by vger.kernel.org with ESMTP id S261396AbVCRAEm (ORCPT ); Thu, 17 Mar 2005 19:04:42 -0500 Date: Thu, 17 Mar 2005 16:04:39 -0800 (PST) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Andrew Morton cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] Prezeroing V8 In-Reply-To: <20050317155908.56e77b8e.akpm@osdl.org> Message-ID: References: <20050317140831.414b73bb.akpm@osdl.org> <20050317151151.47fd6e5f.akpm@osdl.org> <20050317155908.56e77b8e.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1333 Lines: 37 On Thu, 17 Mar 2005, Andrew Morton wrote: > > http://oss.sgi.com/projects/page_fault_performance/ > > Oh no, not that page again ;) Yes indeed! > Seems to say that prezeroing makes negligible difference to kernel builds, > but speeds up a big malloc+memset by 3x to 4x, yes? Correct. > Are there any real-worldish workloads which show an appreciable benefit? Ummm. Big loads are our real-worldish workloads here. > The large speedup for a big memset seems odd - I assume it's simply > transferring CPU load from the user's process over to kscrubd. Or is it > the fancy page-zeroing hardware? How do we differentiate the two? I switched off the page-zeroing hardware for the tests. > Are there any workloads which are seeing a benefit on a CPU which doesn't > have the zeroing hardware? Without zeroing hardware the eroing actions are moved to idle system time (load < /proc/sys/vm/scrub_load). Its shifting the cpu load. But I just fixed things up so that the kernel can return hot zeroed pages to the pool for quicklist management. This yields zeroed pages without kscrubd. - 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/