From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 31 Aug 2005 16:06:12 +0100 (BST) From: Hugh Dickins Subject: Re: [PATCH 1/1] Implement shared page tables In-Reply-To: <16640000.1125498711@[10.10.2.4]> Message-ID: References: <7C49DFF721CB4E671DB260F9@[10.1.1.4]> <1125489077.3213.12.camel@laptopd505.fenrus.org> <16640000.1125498711@[10.10.2.4]> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: "Martin J. Bligh" Cc: Arjan van de Ven , Dave McCracken , Andrew Morton , Linux Kernel , Linux Memory Management List-ID: On Wed, 31 Aug 2005, Martin J. Bligh wrote: > --Hugh Dickins wrote (on Wednesday, August 31, 2005 14:42:38 +0100): > > > > Which is indeed a further disincentive against shared page tables. > > Or shared pagetables a disincentive to randomizing the mmap space ;-) Fair point! > They're incompatible, but you could be left to choose one or the other > via config option. Wouldn't need config option: there's /proc/sys/kernel/randomize_va_space for the whole running system, compatibility check on the ELFs run, and the infinite stack rlimit: enough ways to suppress randomization if it doesn't suit you. > 3% on "a certain industry-standard database benchmark" (cough) is huge, > and we expect the benefit for PPC64 will be larger as we can share the > underlying hardware PTEs without TLB flushing as well. Okay - and you're implying that 3% comes from _using_ the shared page tables, rather than from avoiding the fork/exit overhead of setting them up and tearing them down. And it can't use huge TLB pages because... fragmentation? Hugh -- 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