From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [PATCH] Document huge memory/cache overhead of memory controller in Kconfig Date: Thu, 21 Feb 2008 15:35:38 +1100 References: <20080220122338.GA4352@basil.nowhere.org> <47BC2275.4060900@linux.vnet.ibm.com> In-Reply-To: <47BC2275.4060900@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200802211535.38932.nickpiggin@yahoo.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: balbir@linux.vnet.ibm.com Cc: Andi Kleen , akpm@osdl.org, torvalds@osdl.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Wednesday 20 February 2008 23:52, Balbir Singh wrote: > Andi Kleen wrote: > > Document huge memory/cache overhead of memory controller in Kconfig > > > > I was a little surprised that 2.6.25-rc* increased struct page for the > > memory controller. At least on many x86-64 machines it will not fit into > > a single cache line now anymore and also costs considerable amounts of > > RAM. > > The size of struct page earlier was 56 bytes on x86_64 and with 64 bytes it > won't fit into the cacheline anymore? Please also look at > http://lwn.net/Articles/234974/ BTW. We'll probably want to increase the width of some counters in struct page at some point for 64-bit, so then it really will go over with the memory controller! Actually, an external data structure is a pretty good idea. We could probably do it easily with a radix tree (pfn->memory controller). And that might be a better option for distros. -- 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