On 04/20/2011 01:11 AM, Ingo Molnar wrote: > > * 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 > It's a very good idea. Do we need: kvm get MyInstance-1 which reports all the attributes, or kvm get MyInstance-1 --debug-io-delay-ms which only reports the interested attribute. -- Best Regards, Asias He -- 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
