From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 9 Jul 2006 16:32:32 +0100 (IST) From: Mel Gorman Subject: Re: [PATCH 0/6] Sizing zones and holes in an architecture independent manner V8 In-Reply-To: <20060708114201.GA9419@osiris.boeblingen.de.ibm.com> Message-ID: References: <20060708111042.28664.14732.sendpatchset@skynet.skynet.ie> <20060708114201.GA9419@osiris.boeblingen.de.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: owner-linux-mm@kvack.org Return-Path: To: Heiko Carstens Cc: akpm@osdl.org, davej@codemonkey.org.uk, tony.luck@intel.com, ak@suse.de, bob.picco@hp.com, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, linux-mm@kvack.org List-ID: On Sat, 8 Jul 2006, Heiko Carstens wrote: > On Sat, Jul 08, 2006 at 12:10:42PM +0100, Mel Gorman wrote: >> There are differences in the zone sizes for x86_64 as the arch-specific code >> for x86_64 accounts the kernel image and the starting mem_maps as memory >> holes but the architecture-independent code accounts the memory as present. > > Shouldn't this be the same for all architectures? The comment in the mail is inaccurate because patch 6/6 will account for the kernel image and mem_map as holes for all architectures if it is merged. The patch could be submitted independent of arch-independent zone-sizing. > Or to put it in other words: > why does only x86_64 account the kernel image as memory hole? > >>From Andi Kleen's mails in the thread "[PATCH 0/5] Sizing zones and holes in an architecture independent manner V7" >>> Begin extract <<< > Why is it a performance regression if the image and memmap is accounted > for as holes? How are those regions different from any other kernel > allocation or bootmem allocations for example which are not accounted as > holes? They are comparatively big and cannot be freed. >If you are sure that it makes a measurable difference to performance, There was at least one benchmark/use case where it made a significant difference, can't remember the exact numbers though. It affects the low/high water marks in the VM zone balancer. Especially for the 16MB DMA zone it can make a difference if you account 4MB kernel in there or not. >>> End extract <<< -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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