From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx112.postini.com [74.125.245.112]) by kanga.kvack.org (Postfix) with SMTP id B6B876B005A for ; Thu, 20 Dec 2012 17:40:51 -0500 (EST) Received: by mail-da0-f43.google.com with SMTP id u36so1743029dak.2 for ; Thu, 20 Dec 2012 14:40:50 -0800 (PST) Date: Thu, 20 Dec 2012 14:40:59 -0800 (PST) From: Hugh Dickins Subject: Re: [PATCH] ksm: make rmap walks more scalable In-Reply-To: Message-ID: References: <50D387FD.4020008@oracle.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Sasha Levin , Mel Gorman , Andrew Morton , Ingo Molnar , Petr Holasek , Linux Kernel Mailing List , linux-mm On Thu, 20 Dec 2012, Linus Torvalds wrote: > On Thu, Dec 20, 2012 at 1:49 PM, Sasha Levin wrote: > > On 12/19/2012 08:44 PM, Hugh Dickins wrote: > >> The rmap walks in ksm.c are like those in rmap.c: > >> they can safely be done with anon_vma_lock_read(). > >> > >> Signed-off-by: Hugh Dickins > >> --- > > > > Hi Hugh, > > > > This patch didn't fix the ksm oopses I'm seeing. > > > > This is with both patches applied: > > Looks like another NULL mm pointer in ksmd.. Hugh fixed one in > 2832bc19f666 ("sched: numa: ksm: fix oops in task_numa_placment()"), > this looks like more of the same. > > At a guess, it looks like get_mergeable_page() has a rmap_item with no > mm. No idea how that happened. Hugh? Some race due to something that > depended on the mmap_sem being exclusive, rather than for > read-ownership? No, it's just a misunderstanding: Sasha's problem is with a linux-next that has Petr's NUMA KSM patch in, and we're still ironing known issues out of that one. Not a problem for 3.8-rc1. Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org