Ryan Harper wrote:
* Anthony Liguori <[EMAIL PROTECTED]> [2008-09-22 22:44]:
Can you run the same performance tests with the following patches (using
sync=on instead of cache=off)?
You'll need my aio_init fix too. I suspect this will give equally good
performance to your patch set. That's not saying your patch set isn't
useful, but I would like to get performance to be better for the case
that we're going through the page cache.
I can run the test, but it is orthogonal to the patchset which is
focused on using O_DIRECT and linux-aio.
Actually, I'm now much more interested in using the fd_pool patch with
cache=off. Using it with the sync=on patch is interesting but I'm
curious how close fd_poll + cache=off gets to linux-aio + cache=off.
Supporting linux-aio is going to be a royal pain. I don't know how we
can do a runtime probe of whether we support resfd or not. A build time
probe is going to be lame because we'll be relying on the glibc
headers. Plus, I'm really, really interested in avoiding the
association of cache=off == better performance.
In theory, the dup() + posix-aio should do okay compared to a custom
thread pool. It should have slightly higher latency, but completion
time should be pretty close. That would let us hold off supporting a
thread pool until we're ready to do zero-copy IO (which is the only
argument for a thread pool verses posix-aio).
Regards,
Anthony Liguori
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