From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 8 Jul 2002 17:08:41 -0400 From: Benjamin LaHaise Subject: Re: scalable kmap (was Re: vm lock contention reduction) Message-ID: <20020708170841.Q13063@redhat.com> References: <3D28042E.B93A318C@zip.com.au> <3D293E19.2AD24982@zip.com.au> <20020708080953.GC1350@dualathlon.random> <3D29F868.1338ACF3@zip.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3D29F868.1338ACF3@zip.com.au>; from akpm@zip.com.au on Mon, Jul 08, 2002 at 01:39:04PM -0700 Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Andrea Arcangeli , Linus Torvalds , "Martin J. Bligh" , Rik van Riel , "linux-mm@kvack.org" List-ID: On Mon, Jul 08, 2002 at 01:39:04PM -0700, Andrew Morton wrote: > I think I'll just go for pinning the damn page. It's a spinlock and > maybe three cachelines but the kernel is about to do a 4k memcpy > anyway. And get_user_pages() doesn't show up much on O_DIRECT > profiles and it'll be a net win and we need to do SOMETHING, dammit. Pinning the page costs too much (remember, it's only a win with a reduced copy of more that 512 bytes). The right way of doing it is letting copy_*_user fail on a page fault for places like this where we need to drop locks before going into the page fault handler. -ben -- "You will be reincarnated as a toad; and you will be much happier." -- 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/