From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from max.fys.ruu.nl (max.fys.ruu.nl [131.211.32.73]) by kvack.org (8.8.7/8.8.7) with ESMTP id UAA14208 for ; Wed, 11 Mar 1998 20:02:16 -0500 Date: Thu, 12 Mar 1998 00:11:38 +0100 (MET) From: Rik van Riel Reply-To: Rik van Riel Subject: Re: 2.1.89 broken? In-Reply-To: <199803112237.WAA04217@dax.dcs.ed.ac.uk> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: "Stephen C. Tweedie" Cc: Trond Eivind Glomsrod , linux-kernel@vger.rutgers.edu, linux-mm@kvack.org List-ID: On Wed, 11 Mar 1998, Stephen C. Tweedie wrote: > No, it's not necessarily doing the Right Thing. The trouble is that > there is no balancing between swapping and emptying the page cache. I've still got some Digital Unix-like balancing code lying around... Basically, you can set 3 values for the buffer/page cache, a minimum value, a maximum value and a steal value. When the buffer/page memory is above steal level and the system needs memory, it'll steal memory from the page cache first. A good default would be 25% of main memory. Of course, these values will be sysctl controllable (we still got 8 unused variables in swap_control ;-). > Now, once we've got a single pass which can scavenge BOTH page cache > and swap pages, then we're really going to be cooking on gas. :) For I think we should just copy DU's scheme: - when buffer/page cache is above steal level, we steal that memory - otherwise, we steal in a round-robin fashion from both > now, however, all we're doing is tweaking what is a very very delicate > balance, and as we proved in the 1.2.4 and 1.2.5 swapping disasters, > getting such a change done in a way which doesn't make at least > somebody's performance very much worse is really quite hard to do in > the current way of managing memory. When I was doing the first round > of work on kswap, it was this balance between cache and swap which was > the biggest problem, not the aging of individual pages from either > source. That's why we have sysctl controllable swapping. And now we're talking about it, the sysctl really needs updating too... You can expect these patches RSN (maybe even tomorrow). grtz, Rik. +-------------------------------------------+--------------------------+ | Linux: - LinuxHQ MM-patches page | Scouting webmaster | | - kswapd ask-him & complain-to guy | Vries cubscout leader | | http://www.fys.ruu.nl/~riel/ | | +-------------------------------------------+--------------------------+