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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] Re: [PATCH 0/3] Refactor AIO to allow multiple AIO implementations |
Date: | Tue, 23 Sep 2008 11:09:34 -0500 |
User-agent: | Thunderbird 2.0.0.16 (X11/20080723) |
Ryan Harper wrote:
* Anthony Liguori <address@hidden> [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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