From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f47.google.com (mail-pa0-f47.google.com [209.85.220.47]) by kanga.kvack.org (Postfix) with ESMTP id CE0616B0031 for ; Tue, 29 Oct 2013 15:50:10 -0400 (EDT) Received: by mail-pa0-f47.google.com with SMTP id lf10so507811pab.6 for ; Tue, 29 Oct 2013 12:50:10 -0700 (PDT) Received: from psmtp.com ([74.125.245.105]) by mx.google.com with SMTP id yj4si16714336pac.21.2013.10.29.12.50.06 for ; Tue, 29 Oct 2013 12:50:07 -0700 (PDT) Date: Tue, 29 Oct 2013 19:49:56 +0000 From: Will Deacon Subject: Re: [RFC PATCH 0/2] Implement get_user_pages_fast for ARM Message-ID: <20131029194956.GC24556@mudshark.cambridge.arm.com> References: <1382101634-4723-1-git-send-email-steve.capper@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1382101634-4723-1-git-send-email-steve.capper@linaro.org> Sender: owner-linux-mm@kvack.org List-ID: To: Steve Capper Cc: "linux-arm-kernel@lists.infradead.org" , "linux-mm@kvack.org" , Andrea Arcangeli , Christoffer Dall , Russell King , Zi Shen Lim , "patches@linaro.org" , "linaro-kernel@lists.linaro.org" On Fri, Oct 18, 2013 at 02:07:11PM +0100, Steve Capper wrote: > This patch series implements get_user_pages_fast on ARM. Unlike other > architectures, we do not use IPIs/disabled IRQs as a blocking > mechanism to protect the page table walker. Instead an atomic counter > is used to indicate how many fast gup walkers are active on an address > space, and any code that would cause them problems (THP splitting or > code that could free a page table page) spins on positive values of > this counter. Curious: did you try benchmarking the two schemes? Whilst I expect this algorithm to be better on ARM, exclusive memory accesses aren't free and we're adding code to the fast path. Will -- 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