Date: Thu, 7 Jan 1999 20:53:25 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Alfred Perlstein <bright@hotjobs.com> Cc: Terry Lambert <tlambert@primenet.com>, dyson@iquest.net, pfgiffun@bachue.usc.unal.edu.co, freebsd-hackers@FreeBSD.ORG Subject: Re: questions/problems with vm_fault() in Stable Message-ID: <199901080453.UAA37668@apollo.backplane.com>
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:>
:> Which buffer? The one MFS passed back or the original one that was
:> replaced? I assume you mean that the original buffer is freed and
:> we are now talking about the one MFS passed back, currently under
:> control of FFS, is no longer being used and eventually is ready
:> to be freed again.
:
:Yes, I just thought of a simple idea that may make this a reality, ALL
:pages returned by MFS are marked dirty so that they are 'flushed' to the
:MFS disk no matter what.
:
:Really nothing is done except the fact that the FFS can not 'steal' pages
:from the MFS and try to reuse them because they DO belong to the MFS.
:
:Just an idea for zero copy. (well single copy, kernel to process, instead
:of kernel to kernel to process)
Ick. We can't just mark them dirty, it would cost too much. The
most common filesystem operation is a read. We do not want to force
reads to generate writes back out to swap, which is what marking the
page dirty would do.
:> from the upper VFS layer, but the fact that the lower VFS layer is
:> removing the page from its own map and thus 'looses' track of it -
:> something a vm_alias would solve neatly.
:
:I'm not arguing against your proposals. What I understand I find very
:appealing, I just had an observation about MFS that might be applicable.
:...
:It sounds like it will be great.
:
:-Alfred
Matthew Dillon Engineering, HiWay Technologies, Inc. & BEST Internet
Communications & God knows what else.
<dillon@backplane.com> (Please include original email in any response)
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