Date: Tue, 16 Feb 1999 11:15:44 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: perlsta <bright@cygnus.rush.net> Cc: "John S. Dyson" <dyson@iquest.net>, freebsd-hackers@FreeBSD.ORG Subject: Re: inode / exec_map interlock ? (follow up) Message-ID: <199902161915.LAA37772@apollo.backplane.com> References: <Pine.BSF.3.96.990216140929.10060w-100000@cygnus.rush.net>
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:I've noticed that the 'old' swapper or system seemed to leave a LOT of
:swap still used en it wasn't trully needed. The new system seems to
:reclaim these regeons as soon as they are swapped in. I've noticed the
:new swapper is a bit more 'peppy' but i'm concerned that it is dooing what
:John says.
:
:What's the deal here? Matt, even though your swapper lists pages as
:'free' does it actually keep them around for reuse? What happens when a
:page is READ faulted in, is the backing swap kept allocated to save on IO
:later?
The new swapper fixes a bunch of things, but the main thing you are
probably seeing is the on-the-fly reallocation of swap backing store when
swapping out dirty pages and the semi-on-the-fly deallocation of swap
backing store when a page is dirtied again.
The async I/O swamping problem is so minor it's hardly worth 4 hours
of flying felder carp. It took 5 minutes to fix once someone ( other
then John ) figured out what the problem was. It should be noted that
the original code was documented *solely* as solving a low memory lockup
condition. It said absolutely nothing about limiting parallel I/O.
Anywhere. In fact, in a large-memory configuration the original code
*wouldn't* limit the I/O load because it was scaled to the free page
margin rather then scaled to I/O load.
What a complete and utter waste of time.
-Matt
Matthew Dillon
<dillon@backplane.com>
:One other thing, I has some trouble getting to sleep last night and
:decided to venture into src/sys/vm, the comments are VERY helpful. The
:kind of documentation going on here will really help people get into
:systems programming, it is MUCH appreciated.
:
:-Alfred
:
:
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