From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with ESMTP id E9CA96B01EF for ; Mon, 19 Apr 2010 15:38:51 -0400 (EDT) Date: Mon, 19 Apr 2010 20:39:19 +0100 From: Mel Gorman Subject: Re: error at compaction (Re: mmotm 2010-04-15-14-42 uploaded Message-ID: <20100419193919.GB19264@csn.ul.ie> References: <201004152210.o3FMA7KV001909@imap1.linux-foundation.org> <20100419190133.50a13021.kamezawa.hiroyu@jp.fujitsu.com> <20100419181442.GA19264@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100419181442.GA19264@csn.ul.ie> Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, "linux-mm@kvack.org" , "minchan.kim@gmail.com" , "kosaki.motohiro@jp.fujitsu.com" List-ID: On Mon, Apr 19, 2010 at 07:14:42PM +0100, Mel Gorman wrote: > On Mon, Apr 19, 2010 at 07:01:33PM +0900, KAMEZAWA Hiroyuki wrote: > > > > mmotm 2010-04-15-14-42 > > > > When I tried > > # echo 0 > /proc/sys/vm/compaction > > > > I see following. > > > > My enviroment was > > 2.6.34-rc4-mm1+ (2010-04-15-14-42) (x86-64) CPUx8 > > allocating tons of hugepages and reduce free memory. > > > > What I did was: > > # echo 0 > /proc/sys/vm/compact_memory > > > > Hmm, I see this kind of error at migation for the 1st time.. > > my.config is attached. Hmm... ? > > > > (I'm sorry I'll be offline soon.) > > That's ok, thanks you for the report. I'm afraid I made little progress > as I spent most of the day on other bugs but I do have something for > you. > > First, I reproduced the problem using your .config. However, the problem does > not manifest with the .config I normally use which is derived from the distro > kernel configuration (Debian Lenny). So, there is something in your .config > that triggers the problem. I very strongly suspect this is an interaction > between migration, compaction and page allocation debug. I unexpecedly had the time to dig into this. Does the following patch fix your problem? It Worked For Me. ==== CUT HERE ==== mm,compaction: Map free pages in the address space after they get split for compaction split_free_page() is a helper function which takes a free page from the buddy lists and splits it into order-0 pages. It is used by memory compaction to build a list of destination pages. If CONFIG_DEBUG_PAGEALLOC is set, a kernel paging request bug is triggered because split_free_page() did not call the arch-allocation hooks or map the page into the kernel address space. This patch does not update split_free_page() as it is called with interrupts held. Instead it documents that callers of split_free_page() are responsible for calling the arch hooks and to map the page and fixes compaction. This is a fix to the patch mm-compaction-memory-compaction-core.patch. Signed-off-by: Mel Gorman --- mm/compaction.c | 6 ++++++ mm/page_alloc.c | 3 +++ 2 files changed, 9 insertions(+), 0 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 8f4c518..6218e03 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -184,6 +184,12 @@ static void isolate_freepages(struct zone *zone, } spin_unlock_irqrestore(&zone->lock, flags); + /* split_free_page does not map the pages */ + list_for_each_entry(page, freelist, lru) { + arch_alloc_page(page, 0); + kernel_map_pages(page, 1, 1); + } + cc->free_pfn = high_pfn; cc->nr_freepages = nr_freepages; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 53442fd..b2af4d9 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1211,6 +1211,9 @@ void split_page(struct page *page, unsigned int order) /* * Similar to split_page except the page is already free. As this is only * being used for migration, the migratetype of the block also changes. + * As this is called with interrupts disabled, the caller is responsible + * for calling arch_alloc_page() and kernel_map_page() after interrupts + * are enabled. */ int split_free_page(struct page *page) { -- 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