From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx179.postini.com [74.125.245.179]) by kanga.kvack.org (Postfix) with SMTP id C01F76B004D for ; Fri, 20 Apr 2012 14:29:12 -0400 (EDT) Received: by pbcup15 with SMTP id up15so1698072pbc.14 for ; Fri, 20 Apr 2012 11:29:12 -0700 (PDT) Date: Fri, 20 Apr 2012 11:29:07 -0700 From: Tejun Heo Subject: Re: Weirdness in __alloc_bootmem_node_high Message-ID: <20120420182907.GG32324@google.com> References: <20120417155502.GE22687@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120417155502.GE22687@tiehlicka.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: yinghai@kernel.org, linux-mm@kvack.org, LKML On Tue, Apr 17, 2012 at 05:55:02PM +0200, Michal Hocko wrote: > Hi, > I just come across the following condition in __alloc_bootmem_node_high > which I have hard times to understand. I guess it is a bug and we need > something like the following. But, to be honest, I have no idea why we > care about those 128MB above MAX_DMA32_PFN. > --- > mm/bootmem.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/bootmem.c b/mm/bootmem.c > index 0131170..5adb072 100644 > --- a/mm/bootmem.c > +++ b/mm/bootmem.c > @@ -737,7 +737,7 @@ void * __init __alloc_bootmem_node_high(pg_data_t *pgdat, unsigned long size, > /* update goal according ...MAX_DMA32_PFN */ > end_pfn = pgdat->node_start_pfn + pgdat->node_spanned_pages; > > - if (end_pfn > MAX_DMA32_PFN + (128 >> (20 - PAGE_SHIFT)) && > + if (end_pfn > MAX_DMA32_PFN + (128 << (20 - PAGE_SHIFT)) && > (goal >> PAGE_SHIFT) < MAX_DMA32_PFN) { > void *ptr; > unsigned long new_goal; Regardless of x86 not using it, this is a bug fix and this code path seems to be used by mips at least. Michal, can you please post proper signed-off patch? The code is simply trying to use memory above DMA32 limit if there seems to be enough space (128M) to avoid unnecessarily using DMA32 memory. Thanks. -- tejun -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org