Hello. I've been experimenting with cache tuning on our time share
systems with the aide of a document from Transarc describing how much
memory each of the various buffers takes and what the various switches do
to modify those buffer spaces. I believe I've worked out a reasonable
theory of where we're taking it in the shorts. There are a lot of
processes that run stat(2) against a large number of files on our systems.
In order to reduce the overhead associated with going off to the file
server to retrieve a bunch of stat information, causing delays for the
users, I've cranked up the -stat option to about 10MB worth of data or
27306 stat entries on our heavily loaded machines. This has had a dramatic
effect on our performance and things are definitely improved. However, we
began to see periodic load spikes, quick jumps in the load, followed by a
reasonably fast wind down to normal operating temperature. Thinking that
this might be due to periodically running out of stat entries for our 87500
cache entries, I tried cranking the -stat option all the way up to 87500.
Hey, these machines have hundreds of MB of memory, so let's use it. Then,
the machine I was using for testing wouldn't boot multi-user. Figuring I'd
run it out of kernel virtual memory, I brought the -stat number down to
54612, twice my original estimate of 10MB of data for stat space. The
machine came up multi-user, but after an hour of hard work, it displayed
the same symptoms we saw in November when we experienced a rather serious
memory leak in the Sun4M Kernel module. That is, the load would spiral out
of control and all useful work would come to an end.
Now, the machine is where it was before I began
fine tuning, and I'm wondering if anyone knows how much kernel memory one
can consume on a SunOS 4.X system? Are there ways to expand the amount of
memory available to AFS?
Thanks for your time and any suggestions you might have.
-Brian
