Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261557AbVALXUr (ORCPT ); Wed, 12 Jan 2005 18:20:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261562AbVALXS1 (ORCPT ); Wed, 12 Jan 2005 18:18:27 -0500 Received: from smtp207.mail.sc5.yahoo.com ([216.136.129.97]:32847 "HELO smtp207.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S261560AbVALXRF (ORCPT ); Wed, 12 Jan 2005 18:17:05 -0500 Message-ID: <41E5AFE6.6000509@yahoo.com.au> Date: Thu, 13 Jan 2005 10:16:54 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20041007 Debian/1.7.3-5 X-Accept-Language: en MIME-Version: 1.0 To: Andrew Morton CC: Christoph Lameter , torvalds@osdl.org, ak@muc.de, hugh@veritas.com, linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org Subject: Re: page table lock patch V15 [0/7]: overview References: <41E4BCBE.2010001@yahoo.com.au> <20050112014235.7095dcf4.akpm@osdl.org> <20050112104326.69b99298.akpm@osdl.org> In-Reply-To: <20050112104326.69b99298.akpm@osdl.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1663 Lines: 44 Andrew Morton wrote: > Christoph Lameter wrote: > >>>Do we have measurements of the negative and/or positive impact on smaller >> >> > machines? >> >> Here is a measurement of 256M allocation on a 2 way SMP machine 2x >> PIII-500Mhz: >> >> Gb Rep Threads User System Wall flt/cpu/s fault/wsec >> 0 10 1 0.005s 0.016s 0.002s 54357.280 52261.895 >> 0 10 2 0.008s 0.019s 0.002s 43112.368 42463.566 >> >> With patch: >> >> Gb Rep Threads User System Wall flt/cpu/s fault/wsec >> 0 10 1 0.005s 0.016s 0.002s 54357.280 53439.357 >> 0 10 2 0.008s 0.018s 0.002s 44650.831 44202.412 >> >> So only a very minor improvements for old machines (this one from ~ 98). > > > OK. But have you written a test to demonstrate any performance > regressions? From, say, the use of atomic ops on ptes? > Performance wise, Christoph's never had as much of a problem as my patches because it isn't doing extra atomic operations in copy_page_range. However, it looks like it should be. For the same reason there needs to be an atomic read in handle_mm_fault. And it probably needs atomic ops in other places too, I think. So my patches cost about 7% in lmbench fork benchmark... however, I've been thinking we could take the mmap_sem for writing before doing the copy_page_range which could reduce the need for atomic ops. - 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/