From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <44574E49.3030600@yahoo.com.au> Date: Tue, 02 May 2006 22:19:21 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [patch 00/14] remap_file_pages protection support References: <20060430172953.409399000@zion.home.lan> <4456D5ED.2040202@yahoo.com.au> <4456D85E.6020403@yahoo.com.au> <20060502112409.GA28159@elte.hu> In-Reply-To: <20060502112409.GA28159@elte.hu> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Ingo Molnar Cc: blaisorblade@yahoo.it, Andrew Morton , linux-kernel@vger.kernel.org, Linux Memory Management List-ID: Ingo Molnar wrote: > originally i tested this feature with some minimal amount of RAM > simulated by UML 128MB or so. That's just 32 thousand pages, but still > the improvement was massive: context-switch times in UML were cut in > half or more. Process-creation times improved 10-fold. With this feature > included I accidentally (for the first time ever!) confused an UML shell > prompt with a real shell prompt. (before that UML was so slow [even in > "skas mode"] that you'd immediately notice it by the shell's behavior) Cool, thanks for the numbers. > > the 'have 1 vma instead of 32,000 vmas' thing is a really, really big > plus. It makes UML comparable to Xen, in rough terms of basic VM design. > > Now imagine a somewhat larger setup - 16 GB RAM UML instance with 4 > million vmas per UML process ... Frankly, without > sys_remap_file_pages_prot() the UML design is still somewhat of a toy. Yes, I guess I imagined the common case might have been slightly better, however with reasonable RAM utilisation, fragmentation means I wouldn't be surprised if it does easily get close to that worst theoretical case. My request for numbers was more about the Intel/glibc people than Paolo: I do realise it is a problem for UML. I just like to see nice numbers :) I think UML's really neat, so I'd love to see this get in. I don't see any fundamental sticking point, given a few iterations, and some more discussion. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- 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