Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262099AbUCEUUI (ORCPT ); Fri, 5 Mar 2004 15:20:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262691AbUCEUUI (ORCPT ); Fri, 5 Mar 2004 15:20:08 -0500 Received: from mail.shareable.org ([81.29.64.88]:39559 "EHLO mail.shareable.org") by vger.kernel.org with ESMTP id S262099AbUCEUUF (ORCPT ); Fri, 5 Mar 2004 15:20:05 -0500 Date: Fri, 5 Mar 2004 20:19:55 +0000 From: Jamie Lokier To: Andrew Morton Cc: Andrea Arcangeli , peter@mysql.com, riel@redhat.com, mbligh@aracnet.com, linux-kernel@vger.kernel.org Subject: Re: 2.4.23aa2 (bugfixes and important VM improvements for the high end) Message-ID: <20040305201954.GB7254@mail.shareable.org> References: <20040228072926.GR8834@dualathlon.random> <20040229014357.GW8834@dualathlon.random> <1078370073.3403.759.camel@abyss.local> <20040303193343.52226603.akpm@osdl.org> <1078371876.3403.810.camel@abyss.local> <20040303200704.17d81bda.akpm@osdl.org> <20040304045212.GG4922@dualathlon.random> <20040303211042.33cd15ce.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040303211042.33cd15ce.akpm@osdl.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1043 Lines: 24 Andrew Morton wrote: > We believe that this could cause misbehaviour of such things as the > boehm garbage collector. This patch provides the mprotect() atomicity by > performing all userspace copies under page_table_lock. Can you use a read-write lock, so that userspace copies only need to take the lock for reading? That doesn't eliminate cacheline bouncing but does eliminate the serialisation. Or did you do that already, and found performance is still very low? > It is a judgement call. Personally, I wouldn't ship a production kernel > with this patch. People need to be aware of the tradeoff and to think and > test very carefully. If this isn't fixed, _please_ provide a way for a garbage collector to query the kernel as to whether this race condition is present. -- Jamie - 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/