Date: Tue, 19 Jun 2018 16:08:22 +0800 From: Erich Dollansky <freebsd.ed.lists@sumeritec.com> To: Stefan Esser <se@freebsd.org> Cc: tech-lists <tech-lists@zyxst.net>, freebsd-stable@freebsd.org, freebsd-questions@freebsd.org Subject: Re: lightly loaded system eats swap space Message-ID: <20180619160822.028aedd5.freebsd.ed.lists@sumeritec.com> In-Reply-To: <7fdc922c-ba19-c822-6f6e-d768533a2876@freebsd.org> References: <c8277497-ffcf-0503-490b-96d1b4605af7@zyxst.net> <20180618160855.44d9a0c2.freebsd.ed.lists@sumeritec.com> <ab5d0cb0-13f5-5de8-6189-c0a5c621c6e9@zyxst.net> <20180619094826.75c0c735.freebsd.ed.lists@sumeritec.com> <7fdc922c-ba19-c822-6f6e-d768533a2876@freebsd.org>
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Hi, On Tue, 19 Jun 2018 09:06:42 +0200 Stefan Esser <se@freebsd.org> wrote: > Am 19.06.18 um 03:48 schrieb Erich Dollansky: > > A very long time ago - and not on FreeBSD but maybe on a real BSD - > > I worked with a system that swapped pages out just to bring it back > > as one contiguous block. This made a difference those days. I do > > not know if the code made it out of the university I was working > > at. I just imagine now that the code made it out and is still in > > use with the opposite effect. > > If this was on a VAX, then it was due to a short-coming of the > MMU of the VAX, which used one linear array (in system virtual this could have been the case as they have had many DEC systems. > Nothing of the above applies to any other architecture than the > VAX and thus the swap-out of all user processes serves no purpose > on any other system. It was an implementation detail of the VAX > VM code, not a BSD Unix feature. I know how an MMU works, but I also know how caches work. It still could give a tiny advantage if it is in one piece, even if it is not a requirement to function. Any way, I do not work in this area anymore. Erich
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