From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH 2.5.43-mm2] New shared page table patch References: <63160000.1035056177@baldur.austin.ibm.com> From: ebiederm@xmission.com (Eric W. Biederman) Date: 19 Oct 2002 22:20:47 -0600 In-Reply-To: <63160000.1035056177@baldur.austin.ibm.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Dave McCracken Cc: Bill Davidsen , Andrew Morton , Linux Kernel , Linux Memory Management List-ID: Dave McCracken writes: > 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. Have you considered putting a fixed upper bound on the number of pages tables a page can be mapped into? This would result in the same amount of memory reduction, with what should be very little complexity. I admit there would be a few more demand paging hits, but they should be controllable. And I suspect their performance impact would be lost in the noise. Eric -- 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/