From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262060AbTD3Ekr (ORCPT ); Wed, 30 Apr 2003 00:40:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262063AbTD3Ekr (ORCPT ); Wed, 30 Apr 2003 00:40:47 -0400 Received: from holomorphy.com ([66.224.33.161]:28880 "EHLO holomorphy") by vger.kernel.org with ESMTP id S262060AbTD3Ekn (ORCPT ); Wed, 30 Apr 2003 00:40:43 -0400 Date: Tue, 29 Apr 2003 21:52:59 -0700 From: William Lee Irwin III To: Andrew Morton Cc: linux-kernel@vger.kernel.org Subject: Re: must-fix list for 2.6.0 Message-ID: <20030430045259.GD8978@holomorphy.com> Mail-Followup-To: William Lee Irwin III , Andrew Morton , linux-kernel@vger.kernel.org References: <20030429155731.07811707.akpm@digeo.com> <20030430031914.GC8978@holomorphy.com> <20030429214537.7c6a6aaf.akpm@digeo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030429214537.7c6a6aaf.akpm@digeo.com> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org William Lee Irwin III wrote: >> I didn't notice anything specific here about sys_remap_file_pages() vs. >> truncate() (sans objrmap); did a fix fly by that I didn't notice, >> or was it less of an issue than I thought it was? On Tue, Apr 29, 2003 at 09:45:37PM -0700, Andrew Morton wrote: > That's just a bug. We can either go through and unmap all the pages via > their rmap chains, or mark the vma as nonlinear and just anonymise the pages > and to heck with the SIGBUS. I'm not particularly fussed either way > really... Okay, I'll just fill in if no one else appears to do the busywork. William Lee Irwin III wrote: >> Also, the OOM killer fails to check lowmem; basically it just needs >> - if (nr_swap_pages > 0) >> + if (nr_swap_pages > 0 && nr_free_buffer_pages() > 0) >> With that in addition to the OOM killer locking patch I posted and >> another to completely eliminate mm-less processes from consideration >> 64GB ia32 (with, of course, my oversized out-of-tree patch) recovers >> from OOM instead of deadlocking after a mass-killing with swap online. On Tue, Apr 29, 2003 at 09:45:37PM -0700, Andrew Morton wrote: > Wanna send patch? Absolutely; I'll arrange a more organized presentation around Thursday (yes, I'm among the last-minute OLS people -- it couldn't be helped). William Lee Irwin III wrote: >> I'd be interested in more detailed descriptions of the user-level no >> overcommit, dcacheicache, and truncated ext3 page issues after Thursday. On Tue, Apr 29, 2003 at 09:45:37PM -0700, Andrew Morton wrote: > The arithmetic in vm_enough_memory() is woefully inaccurate. If you have no > swap and then build up a lot of icache/dcache, vm_enough_memory() > underestimates the amount of reclaimable memory by a lot and big mallocs > fail. If the i/dcache has internal fragmentation it gets even worse. > I had a brief poke at that a while ago and decided it was basically hopeless. > I suspect that assuming "all slab pages are reclaimable" would be the best > fix here. It sounds like some thought may be necessary if the above approach is to be improved upon. On Tue, Apr 29, 2003 at 09:45:37PM -0700, Andrew Morton wrote: > The ext3 truncate pages are those pages which are on the LRU and have > buffers, but that's _all_ they have. They are instantly reclaimable and are > basically free memory. Only nobody knows that yet, so vm_enough_memory() > gets it wrong. The fix would be to nail these pages more aggressively in > journal_unmap_buffer(), or to account for them and include that accounting in > vm_emough_memory(). I'd prefer to just free the dang pages in > journal_unmap_buffer(). Noted. William Lee Irwin III wrote: >> The latter sounds easy to address. It actually sounds like a 2.4.x >> compatibility fix. On Tue, Apr 29, 2003 at 09:45:37PM -0700, Andrew Morton wrote: > davem thinks we shouldn't need it, and I've seen no bug reports that indicate > that we _do_ need it, but Andi says we do. > Certainly something needs to be done in that area - a ppc64 box with 16G of > memory (all ZONE_DMA) cruises along with just 1M of memory free. Okay, I'll classify that as a back-burner issue. Thanks. -- wli