From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 19 Oct 2002 14:36:17 -0500 From: Dave McCracken Subject: Re: [PATCH 2.5.43-mm2] New shared page table patch Message-ID: <63160000.1035056177@baldur.austin.ibm.com> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: Bill Davidsen Cc: Andrew Morton , Linux Kernel , Linux Memory Management List-ID: --On Saturday, October 19, 2002 15:17:31 -0400 Bill Davidsen wrote: > Don't tease, what did that do for performance? I see that someone has > already posted a possible problem, and the code would pass for complex for > most people, so is the gain worth the pain? I posted some fork/exec/exit microbenchmark results last week, in which for large processes fork becomes much faster, and exec/exit become much faster for processes with lots of shared memory. As for results from larger benchmarks, those haven't been done. The TPC-H test we used was primarily for stability testing, and secondarily to see if we could reduce page table/pte_chain memory overhead, which we did. The pte_chain overhead was reduced by close to a factor of 100. This patch isn't primarily a performance patch. It does help for some things, notably the fork/exec/exit cases mentioned above. But its primary goal is to reduce the amount of memory wasted in page tables mapping the same pages into multiple processes. We have seen an application that consumed on the order of 10 GB of page tables to map a single shared memory chunk across hundreds of processes. Shared page tables would eliminate this overhead. Dave McCracken ====================================================================== Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059 dmccr@us.ibm.com T/L 678-3059 -- 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/