Hello,
if recently read [Dougan99], which describes optimizations to the memory
management system of the PowerPC port of the Linux kernel. One of the
mechanisms (Section 9) is pushing the clearing of pages to the idle task,
like FreeBSD does.
The authors report that on the PPC architecture, it is critical that the
data and instruction cache be turned off before zeroing pages in the idle
loop. Otherwise, cache pollution as a side-effect of idle-time activity
would more than cancel out the gains from the zeroing.
Wouldn't this be true on the i386 architecture as well? I have seen no
calls in the FreeBSD idle loop that seem to do this. I'm not even sure if
the i386 architecture supports turning off caches (but a quick glance at
the Pentium references seems to indicate so.) Has anybody experimented with
the idea before?
Lars
[Dougan99] Cort Dougan, Paul Mackerras and Victor Yodaiken. Optimizing
the Idle Task and Other MMU Tricks. Proceedings 3rd USENIX Symposium
on Operating Systems Design and Implementation (OSDI), February 1999,
pp. 229-237.
--
Lars Eggert <[EMAIL PROTECTED]> Information Sciences Institute
http://www.isi.edu/larse/ University of Southern California
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