From owner-freebsd-current@FreeBSD.ORG Mon Jun 7 16:26:19 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7517716A4CE; Mon, 7 Jun 2004 16:26:19 +0000 (GMT) Received: from canning.wemm.org (canning.wemm.org [192.203.228.65]) by mx1.FreeBSD.org (Postfix) with ESMTP id 576C443D66; Mon, 7 Jun 2004 16:26:19 +0000 (GMT) (envelope-from peter@evilpete.dyndns.org) Received: from fw.wemm.org (canning.wemm.org [192.203.228.65]) by canning.wemm.org (Postfix) with ESMTP id CFA4F2A7EA; Mon, 7 Jun 2004 09:26:18 -0700 (PDT) (envelope-from peter@overcee.wemm.org) Received: from overcee.wemm.org (overcee.wemm.org [10.0.0.3]) by fw.wemm.org (Postfix) with ESMTP id 0BF0EE29E; Mon, 7 Jun 2004 09:26:17 -0700 (PDT) (envelope-from peter@overcee.wemm.org) Received: from overcee.wemm.org (localhost [127.0.0.1]) by overcee.wemm.org (8.12.11/8.12.11) with ESMTP id i57GQHVY022152; Mon, 7 Jun 2004 09:26:17 -0700 (PDT) (envelope-from peter@overcee.wemm.org) Received: from localhost (localhost [[UNIX: localhost]]) by overcee.wemm.org (8.12.11/8.12.11/Submit) id i57GQBKJ022151; Mon, 7 Jun 2004 09:26:11 -0700 (PDT) (envelope-from peter) From: Peter Wemm To: Thomas Moestl Date: Mon, 7 Jun 2004 09:26:11 -0700 User-Agent: KMail/1.6.1 References: <40C36D31.4010003@freebsd.org> <20040606215921.GA96205@xor.obsecurity.org> <20040607143332.GA1311@timesink.dyndns.org> In-Reply-To: <20040607143332.GA1311@timesink.dyndns.org> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200406070926.11289.peter@wemm.org> cc: hackers@freebsd.org cc: current@freebsd.org cc: peter@freebsd.org cc: Kris Kennaway Subject: Re: HEADS UP! KSE needs more attention X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 Jun 2004 16:26:19 -0000 On Monday 07 June 2004 07:33 am, Thomas Moestl wrote: > On Sun, 2004/06/06 at 14:59:21 -0700, Kris Kennaway wrote: > > On Sun, Jun 06, 2004 at 03:49:13PM -0600, Scott Long wrote: > > > amd64 is approaching critical mass for tier-1. There are a > > > number of developers that own amd64 hardware now, and a number of > > > users who are asking about it on the mailing lists. Peter is > > > finishing up the last blocking item for it (kld's) not including > > > the observed KSE problems. It's very close and I _will_ hold up > > > the release for it to get done. amd64 is the future of commodity > > > computing and we aren't going to ignore it for 5-STABLE. > > > > amd64 has a bug with swapping - when something begins to access > > swap, the entire system becomes almost entirely unresponsive (e.g. > > no mouse response for up to 10 seconds) until it stops. Peter has > > some ideas about it, but it's a serious enough bug that it forced > > me to stop using amd64 as my desktop machine (hello, kde!). > > Hmmm, I have encountered a similar problem on sparc64 once; the > reason was that vm_pageout_map_deactivate_pages() calls > pmap_remove() for the range from the start to the end of the > process's vm_map when a process is swapped out. Start and end > are VM_MIN_ADDRESS and VM_MAXUSER_ADDRESS respectively, and on > 64-bit architectures, that range is very large (128TB on ia64 > if I'm not mistaken), so the iteration in pmap_remove() must > be carefully designed to make as large steps as possible to > avoid long run times (or to not iterate over the range at all > if it becomes too large, which we did on sparc64). > > It seems that the amd64 version of pmap_remove() will essentially > always iterate in 2MB (level 2 page table) steps, regardless of > whether there is mapping for the respective level 2 table in the > table levels above; that means that in the previously mentioned case, > the outer loop will usually run for about 67 million iterations (the > resident count guard may not be of much use here if a stack page is > left at the very end of the address space). Since there are a few > memory accesses needed in each iterations, that may already be the > cause of such a delay. You know, this sounds spot-on! Thanks for the tip! -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com "All of this is for nothing if we don't go to the stars" - JMS/B5