From owner-freebsd-arch Wed May 16 10:26:53 2001 Delivered-To: freebsd-arch@freebsd.org Received: from earth.backplane.com (earth-nat-cw.backplane.com [208.161.114.67]) by hub.freebsd.org (Postfix) with ESMTP id 3F4FD37B422 for ; Wed, 16 May 2001 10:26:50 -0700 (PDT) (envelope-from dillon@earth.backplane.com) Received: (from dillon@localhost) by earth.backplane.com (8.11.3/8.11.2) id f4GHQg472438; Wed, 16 May 2001 10:26:42 -0700 (PDT) (envelope-from dillon) Date: Wed, 16 May 2001 10:26:42 -0700 (PDT) From: Matt Dillon Message-Id: <200105161726.f4GHQg472438@earth.backplane.com> To: Terry Lambert Cc: Rik van Riel , arch@FreeBSD.ORG, linux-mm@kvack.org, sfkaplan@cs.amherst.edu Subject: Re: on load control / process swapping References: <3B00CECF.9A3DEEFA@mindspring.com> <200105151724.f4FHOYt54576@earth.backplane.com> <3B0238EB.DF435099@mindspring.com> Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :I think a lot of the "administrative limits" are stupid; :in particular, I think it's really dumb to have 70% free :resources, and yet enforce administrative limits as if all :... The 'memoryuse' resource limit is not enforced unless the system is under memory pressure. :... :> And without being able to make the prediction :> accurately you simply cannot determine how much data :> you should try to cache before you begin recycling it. : :I should think that would be obvious: nearly everything :you can, based on locality and number of concurrent :references. It's only when you attempt prefetch that it :actually becomes complicated; deciding to throw away a :clean page later instead of _now_ costs you practically :nothing. :... Prefetching has nothing to do with what we've been talking about. We don't have a problem caching prefetched pages that aren't used. The problem we have is determining when to throw away data once it has been used by a program. :... :> So the jist of the matter is that FreeBSD (1) already :> has process-wide working set limitations which are :> activated when the system is under load, : :They are largely useless, since they are also active even :when the system is not under load, so they act as preemptive :... This is not true. Who told you this? This is absolutely not true. :drags on performance. They are also (as was pointed out in :an earlier thread) _not_ applied to mmap() and other regions, :so they are easily subverted. :... : :-- Terry : This is not true. The 'memoryuse' limit applies to all in-core pages associated with the process, whether mmap()'d or not. -Matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message