* Sasha Levin <levinsasha928@xxxxxxxxx> wrote: > On Tue, 2011-04-19 at 19:52 +0300, Pekka Enberg wrote: > > On Mon, Apr 18, 2011 at 4:02 PM, Sasha Levin <levinsasha928@xxxxxxxxx> wrote: > > > Add --debug-io-delay-cycles and --debug-io-delay-amount to delay the completion of IO requests within virtio-blk. > > > This feature allows to verify and debug the threading within virtio-blk. > > > > > > Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx> > > > > Well, to be honest, I'm not convinced we need both of these. Isn't > > --debug-io-delay=<msec> enough for our use? > > This came up during our testing. > > Ingo suggested a large delay so we could easily see the results of > threading. The problem we encountered was that having a delay right from > the beginning will make the guest kernel take a rather long time to boot > and would make actually testing the threading impossible. > > I've added a delay before the activation of the I/O request completion > delay to give the tester/debugger enough time to boot into the guest and > prepare anything needed for the test. > > Making it a constant is also rather hard because different kernels can > take a very different amount of I/O requests to boot. Take the simple > example of a whether fsck was running during the boot or not. I suspect we'll eventually want to have some sort of 'kvm set' subcommand that can modify attributes of running instances? Setting the debug delay would be one of the options: kvm set MyInstance-1 --debug-io-delay-ms 10000 That way the delay can be activated in a suitable moment - and disabled again after testing: kvm set MyInstance-1 --debug-io-delay-ms 0 ? Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
