I just puhsd 8.0.3 to production on Sunday, and haven't had a time to
really monitor it under load, so I can't tell if it's helped the context
switch problem yet or not.
Neil Conway wrote:
Tom Arthurs wrote:
Yes, shared buffers in postgres are not used for caching
Shared buffers in Postgres _are_ used for caching, they just form a
secondary cache on top of the kernel's IO cache. Postgres does IO
through the filesystem, which is then cached by the kernel. Increasing
shared_buffers means that less memory is available for the kernel to
cache IO -- increasing shared_buffers has been shown to be a net
performance loss beyond a certain point. Still, there is value in
shared_buffers as it means we can avoid a read() system call for hot
pages. We can also do better buffer replacement in the PG shared buffer
than the kernel can do (e.g. treating IO caused by VACUUM specially).
My biggest challenge with solaris/sparc is trying to reduce context
switching.
It would be interesting to see if this is improved with current sources,
as Tom's bufmgr rewrite should have hopefully have reduced this problem.
-Neil
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