From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 17 Sep 2006 19:20:10 -0700 From: Paul Jackson Subject: Re: [PATCH] GFP_THISNODE for the slab allocator Message-Id: <20060917192010.cc360ece.pj@sgi.com> In-Reply-To: References: <20060914220011.2be9100a.akpm@osdl.org> <20060914234926.9b58fd77.pj@sgi.com> <20060915002325.bffe27d1.akpm@osdl.org> <20060915004402.88d462ff.pj@sgi.com> <20060915010622.0e3539d2.akpm@osdl.org> <20060917041707.28171868.pj@sgi.com> <20060917060358.ac16babf.pj@sgi.com> <20060917152723.5bb69b82.pj@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: David Rientjes Cc: clameter@sgi.com, akpm@osdl.org, linux-mm@kvack.org List-ID: David wrote: > > Given two node numbers, are they really just two fake nodes > > on the same hardware node, or are they really on two distinct > > hardware nodes? > > > > The cpumap for all fake nodes are always 00000000 except for node0 which > reports the true hardware configuration. Thanks. I doubt that this is a unique signature identifying fake numa systems. I've seen other systems that had memory-only nodes, which I suspect would show up with all 000000 cpumaps on those nodes. Perhaps we should add a hook to allow testing if we are running on fake numa system: For example, we could add a macro to a header that, in the case CONFIG_NUMA_EMU was enabled, evaluated to 1 if numa emulation was enabled. Currently, the true state of numa emulation only seems to be known to code within: arch/x86_64/mm/numa.c and currently only available for x86_64 arch's and only available if CONFIG_NUMA_EMU is enabled. With the usual conditional macro header magic, we could make a test for NUMA emulation available in generic kernel code. Andrew, Do you have any plans to build a hybrid system with both real and emulated NUMA present? That could complicate things. My current notion is to have a simple modal switch: - Fake numa systems would never try to go-back-to-the-earlier-zone. - Real NUMA systems not use this zone caching at all, always scanning the zonelist from the front. Such trivial modal behaviour wouldn't work on a hybrid system with both real and emulated NUMA. -- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson 1.925.600.0401 -- 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