From owner-freebsd-hackers  Wed Jul 19 21:41:31 2000
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Date: Wed, 19 Jul 2000 23:41:24 -0500
From: Alan Cox <alc@cs.rice.edu>
To: Lars Eggert <larse@isi.edu>
Cc: hackers@freebsd.org
Subject: Re: clearing pages in the idle loop
Message-ID: <20000719234124.H14543@cs.rice.edu>
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Last year, I tried to reproduce some of the claims/results
in this paper on FreeBSD/x86 and couldn't.  I also tried
limiting the idle loop to clearing pages of one particular
color at a time.  That way, the cache lines replaced by
the second page you clear are the cache lines holding
the first page you cleared, and so on for the third,
fourth, ... pages cleared.  Again, I saw no measurable
effect on tests like "buildworld", which is a similar
workload to the paper's if I recall correctly.

Finally, it's possible that having these pre-zeroed pages
in your L2 cache might be beneficial if they get allocated
and used right away.  FreeBSD's idle loop zeroes the pages
that are next in line for allocation.

Alan


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