From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gerd Hoffmann Subject: Re: [PATCH] turn off writable page tables Date: Wed, 26 Jul 2006 10:18:03 +0200 Message-ID: <44C7253B.9080906@suse.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ian Pratt Cc: Andrew Theurer , xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Hi, > I'd like to make sure there's no 'dumb stuff' happening, and the > writeable pagetables isn't being used erroneously where we don't expect > it (hence crippling the scores), and that its actually functioning as > intended i.e. that we get one fault to unhook, and then a fault causing > a rehook once we move to the next page in the fork. > > If you write a little test program that dirties a large chunk of memory > just before the fork, we should see writeable pagetables winning easily. Just an idea: Any chance mm_pin() and mm_unpin() cause this? The bulk page table updates for the new process created by fork() are not seen by xen anyway I think. The first schedule of the new process triggers pinning, i.e. r/o mapping and verification ... cheers, Gerd -- Gerd Hoffmann http://www.suse.de/~kraxel/julika-dora.jpeg