From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 8 Jun 2001 18:10:07 -0300 (BRT) From: Marcelo Tosatti Subject: Re: Background scanning change on 2.4.6-pre1 In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: "David S. Miller" , Mike Galbraith , Zlatko Calusic , linux-mm@kvack.org List-ID: On Fri, 8 Jun 2001, Linus Torvalds wrote: > > > On Fri, 8 Jun 2001, Marcelo Tosatti wrote: > > > > I've tried that in the past, and the behaviour I got was pages being > > swapped out with little (or not any) VM pressure. > > What is "past"? > > Remember: these days we don't do any IO at all inside "swap_out()", the > _only_ thing we do is to age the VM and possibly move pages to the swap > cache. Yes, in the days where we did actual swapouts at page_launder(). > Which is really what you wanted - it's just that we delay moving anonymous > pages to the swap-cache until we have some reason to (ie we delay it until > we want to re-fill the inactive list). > > Think of it as a simple issue of > - when we age pages, we should also check whether they've been dirtied by > being mapped, and whether the mappings have accessed them. > > Put that way, I doubt you'll disagree. I agree. > (Now, whether it gets the balancing _right_ is another matter altogether. > We may have to tune the amount of pages that get looked at, both on the VM > mapping side and on the active/inactive list sides). > > We actually always used to do this, it was just that we delayed it until > the active list scan started failing. Which may have been delaying it too > much, causing "spikes" of activity. > > Or maybe not. I'd like people to explore the balancing space more, instead > of trying to tune specific parts of the existing balance. > > > Yes, we want fair aging. No, we dont want more pages being swapped out. > > Absolutely. "swap_out()" does not really swap pages out. The name is > purely due to historical reasons. It should really be called > "scan_process_mappings()" or similar. > > The actual swap-out obviously happens in page_launder(). Yes. Now the problem is having swap space allocated with _NO_ pressure may sound a bit weird to people. _I_ know that we're just allocating the swap space, but not everybody does. -- 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/