Re: VM Requirement Document - v0.0

From: Martin Knoblauch (
Date: Wed Jun 27 2001 - 03:53:12 EST

>> * If we're getting low cache hit rates, don't flush
>> processes to swap.
>> * If we're getting good cache hit rates, flush old, idle
>> processes to swap.

Rik> ... but I fail to see this one. If we get a low cache hit rate,
Rik> couldn't that just mean we allocated too little memory for the
Rik> cache ?

 maybe more specific: If the hit-rate is low and the cache is already
70+% of the systems memory, the chances maybe slim that more cache is
going to improve the hit-rate.

 I do not care much whether the cache is using 99% of the systems memory
or 50%. As long as there is free memory, using it for cache is great. I
care a lot if the cache takes down interactivity, because it pushes out
processes that it thinks idle, but that I need in 5 seconds. The caches
pressure against processes should decrease with the (relative) size of
the cache. Especially in low hit-rate situations.

 OT: I asked the question before somewhere else. Are there interfaces to
the VM that expose the various cache sizes and, more important,
hit-rates to userland? I would love to see (or maybe help writing in my
free time) a tool to just visualize/analyze the efficiency of the VM


Martin Knoblauch         |    email:
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This archive was generated by hypermail 2b29 : Sat Jun 30 2001 - 21:00:16 EST