Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161031AbVICBkj (ORCPT ); Fri, 2 Sep 2005 21:40:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161074AbVICBki (ORCPT ); Fri, 2 Sep 2005 21:40:38 -0400 Received: from smtp208.mail.sc5.yahoo.com ([216.136.130.116]:31608 "HELO smtp208.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S1161031AbVICBki (ORCPT ); Fri, 2 Sep 2005 21:40:38 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=h0Os0tBbw51AiT7QC3AHMD3Kpwxr+HMRB36at4Tqo00JjtXpQrlfm6a4gG3nlcTwpYQEMnewWpIP3hFX1iMvFsy20YCedeRZ6UcpQM2xfzdl1ItZRelQxE4UsdMPn5QQoPjXikYVYV5kJOKzQuodZhZ4sCYIS0HKQHaZ3WrdaTw= ; Message-ID: <4318FF2B.6000805@yahoo.com.au> Date: Sat, 03 Sep 2005 11:40:59 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.10) Gecko/20050802 Debian/1.7.10-1 X-Accept-Language: en MIME-Version: 1.0 To: Alan Cox CC: Andi Kleen , Linux Memory Management , linux-kernel Subject: Re: [PATCH 2.6.13] lockless pagecache 2/7 References: <4317F071.1070403@yahoo.com.au> <4317F0F9.1080602@yahoo.com.au> <4317F136.4040601@yahoo.com.au> <1125666486.30867.11.camel@localhost.localdomain> <4318C28A.5010000@yahoo.com.au> <1125705471.30867.40.camel@localhost.localdomain> In-Reply-To: <1125705471.30867.40.camel@localhost.localdomain> 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: 1110 Lines: 34 Alan Cox wrote: >>but I suspect that SMP isn't supported on those CPUs without ll/sc, >>and thus an atomic_cmpxchg could be emulated by disabling interrupts. > > > It's obviously emulatable on any platform - the question is at what > cost. For x86 it probably isn't a big problem as there are very very few > people who need to build for 386 any more and there is already a big > penalty for such chips. > > Thanks Alan, Dave, others. We'll see how things go. I'm fairly sure that for my usage it will be a win even if it is costly. It is replacing an atomic_inc_return, and a read_lock/read_unlock pair. But if it does one day get merged, and proves to be very costly on some architectures then we'll need to be careful about where it gets used. Nick -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com - 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/