From: Jeff Dike <jdike@ka...> - 2002-01-25 18:55:19
> Here are the chagnes for do_io to use the io_req error for error
> reporting rather than having the error status returned and then used
> to set io_req.error.
I'm a bit dubious about this one. It's a little cleaner (by removing knowlege
of the io_req from io_thread), but it also adds code. I put it in, but that's
right on the border.
> Sometime in the future we may want to have multiple threads
That will not happen.
> or to use async read/write to handle the multiple ubd devices.
This will. Not just for multiple ubd devices. They will still use one
queue. AIO will let us submit many requests to the host at once, which
will let readahead work.
Ben LaHaise has released his AIO patch. If you want to make this driver
support multiple outstanding requests, patch the host, and port ubd to
use AIO. I'd be interested in what kind of performance increase you get
on IO-intensive things.
> Currently the
> entire block io subsystem is single threaded which is simple but