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Re: memory_object_lock_request and memory_object_data_return fnord

From: Thomas Bushnell, BSG
Subject: Re: memory_object_lock_request and memory_object_data_return fnord
Date: 27 Mar 2002 15:12:41 -0800
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.1

Neal H Walfield <neal@cs.uml.edu> writes:

> > I think we should certainly use vm_copy for whole-page copies in
> > pager_memcpy because of the badly suboptimal behavior you've described.
> I have cooked up the attached implementation.  I checked everything
> but a few border cases -- I need to write a few more tests.  Perhaps,
> I will get to it this weekend.  However, I am interested in some
> feedback.

One thing I think of looking at.

It may well be that for smaller number of pages, memcpy is actually
more efficient than vm_copy because of the constant overhead in the
latter function.

So I'd like to see some instrumentation of where that cutoff actually

Until that's done, I have no problem with assuming any particular sane
value for the cutoff, but I think your function should have a tunable
parameter for it.


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