Date: Wed, 16 May 2001 10:26:42 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: Terry Lambert <tlambert2@mindspring.com> Cc: Rik van Riel <riel@conectiva.com.br>, arch@FreeBSD.ORG, linux-mm@kvack.org, sfkaplan@cs.amherst.edu Subject: Re: on load control / process swapping Message-ID: <200105161726.f4GHQg472438@earth.backplane.com> References: <Pine.LNX.4.21.0105131417550.5468-100000@imladris.rielhome.conectiva> <3B00CECF.9A3DEEFA@mindspring.com> <200105151724.f4FHOYt54576@earth.backplane.com> <3B0238EB.DF435099@mindspring.com>
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: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
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