From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Woodhouse In-Reply-To: <200006281554.KAA19007@jen.americas.sgi.com> References: <200006281554.KAA19007@jen.americas.sgi.com> Subject: Re: kmap_kiobuf() Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Wed, 28 Jun 2000 17:06:30 +0100 Message-ID: <13214.962208390@cygnus.co.uk> Sender: owner-linux-mm@kvack.org Return-Path: To: lord@sgi.com Cc: linux-kernel@vger.rutgers.edu, linux-mm@kvack.org, sct@redhat.com, riel@conectiva.com.br List-ID: lord@sgi.com said: > I always knew it would go down like a ton of bricks, because of the > TLB flushing costs. As soon as you have a multi-cpu box this operation > gets expensive, the code could be changed to do lazy tlb flushes on > unmapping the pages, but you still have the cost every time you set a > mapping up. Aha - is this why kmap uses a pre-allocated set of PTEs? I got about that far before deciding I had no clue what was going on and giving up. MM is not exactly my field - I just know I want to be able to lock down a user's buffer and treat it as if it were in kernel-space, passing its address to functions which expect kernel buffers. -- dwmw2 -- 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/