Re: [uml-devel] UBD performance

[Jeff D. <jd...@ad...>]

On Mon, Oct 10, 2005 at 10:10:24AM +0100, Chris Lightfoot wrote:
> OK. The host is indeed using a 4K block filesystem; I
> couldn't find your O_DIRECT patch, but turning on O_DIRECT
> with fcntl just after opening the backing file gives these
> results:
>     http://ex-parrot.com/~chris/tmp/20051010/host-vs-uml-io-results-3.png
> i.e., the AIO implementation is now slower than the stock
> implementation for writes of size up to about 8KB, but
> faster for larger writes; it's still quite a bit slower
> than the host.

There aren't very good labels on that graph, but it looks consistent with my
experience, which is 25-30% faster kernel builds with AIO/O_DIRECT.

The next question is where the slowdown is happening.

				Jeff