From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: 3rd version of R/W mmap_sem patch available References: <3AB77311.77EB7D60@uow.edu.au> <3AB77443.55B42469@mandrakesoft.com> <3AB777E1.2B233E8A@uow.edu.au> From: ebiederman@lnxi.com (Eric W. Biederman) Date: 20 Mar 2001 18:59:27 -0700 In-Reply-To: Andrew Morton's message of "Wed, 21 Mar 2001 02:31:45 +1100" Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Jeff Garzik , Linus Torvalds , linux-mm@kvack.org List-ID: Andrew Morton writes: > Jeff Garzik wrote: > > > > Andrew Morton wrote: > > > General comment: an expensive part of a pagefault > > > is zeroing the new page. It'd be nice if we could > > > drop the page_table_lock while doing the clear_user_page() > > > and, if possible, copy_user_page() functions. Very nice. > > > > People have talked before about creating zero pages in the background, > > or creating them as a side effect of another operation (don't recall > > details), so yeah this is definitely an area where some optimizations > > could be done. I wouldn't want to do it until 2.5 though... > > Actually, I did this for x86 last weekend :) Initial results are > disappointing. > > It creates a special uncachable mapping and sits there > zeroing pages in a low-priority thread (also tried > doing it in the idle task). Well if you are going to mess with caching make the mapping write-combining on x86.. You get much better performance. 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.eu.org/Linux-MM/