From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 22 Nov 2004 15:16:28 -0800 From: Andrew Morton Subject: Re: deferred rss update instead of sloppy rss Message-Id: <20041122151628.77ab87ca.akpm@osdl.org> In-Reply-To: References: <20041122141148.1e6ef125.akpm@osdl.org> <20041122144507.484a7627.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: hugh@veritas.com, torvalds@osdl.org, benh@kernel.crashing.org, nickpiggin@yahoo.com.au, linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org List-ID: Christoph Lameter wrote: > > On Mon, 22 Nov 2004, Andrew Morton wrote: > > > > The page fault code only increments rss. For larger transactions that > > > increase / decrease rss significantly the page_table_lock is taken and > > > mm->rss is updated directly. So no > > > gross inaccuracies can result. > > > > Sure. Take a million successive pagefaults and mm->rss is grossly > > inaccurate. Hence my suggestion that it be spilled into mm->rss > > periodically. > > It is spilled into mm->rss periodically. That is the whole point of the > patch. > > The timer tick occurs every 1 ms. That only works if the task happens to have the CPU when the timer tick occurs. There remains no theoretical upper bound to the error in mm->rss, and that's very easy to fix. -- 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: aart@kvack.org