Gregory Stark wrote:
Simon Riggs <[EMAIL PROTECTED]> writes:
I'm happy with the idea of a readahead process. I thought we were
implementing a BackgroundReader process for other uses. Is that dead
now?
You and Bruce seem to keep resurrecting that idea. I've never liked it -- I
always hated that in Oracle and thought it was a terrible kludge.
I think the inter-process communication would be way too heavy-weight, by the
time the other process is schedule the process which needed the blocks would
have probably have done many of them already anyways. Worse, you would need a
large number of reading processes and would start to run into locking
contention on the work-queue as well.
In any case it would be a lot of code to do what posix_fadvise does for us
with a simple syscall anyways.
I agree.
Am I misjudging this? Is this a popular idea? We could always implement it as
a fall-back implementation for mdprefetch() where posix_fadvise (and libaio
assuming we implement that as well) don't work. It has the advantage of
working with any system at all even if it predates 1003.1.
Yeah, if we want to support prefetching on systems that don't have
posix_fadvise(), that would be the way to do it. posix_fadvise() is a
good API. We can support multiple platform-specific implementations of
it if there's interest, using posix_fadvise(), aio to a dummy buffer,
whatever functions there's on Windows, or background reader processes or
threads.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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