On Fri, May 07, 2010 at 01:03:28PM +0930, Rusty Russell wrote: > On Thu, 6 May 2010 03:49:46 pm Michael S. Tsirkin wrote: > > Now, I also added an mb() in guest between read and write so > > that last used index write can not get ahead of used index read. > > It does feel good to have it there, but I can not say why > > it's helpful. Works fine without it, but then these > > subtle races might be hard to trigger. What do you think? > > I couldn't see that in the patch? I don't think it's necessary > though, since the write of depends last_used depends on the read of > used (and no platform we care about would reorder such a thing). Well, there's no data dependency, is there? > I'm reasonably happy, but we should write some convenient test for > missing interrupts. > > I'm thinking of a sender which does a loop: blasts 1MB of UDP packets, > then prints the time and sleep(1). The receiver would print the time > every 1MB of received data. The two times should almost exactly correspond. > > Assuming that the network doesn't overflow and lose stuff, this should > identify any missing wakeup/interrupts (depending on direction used). > > Cheers, > Rusty. -- 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
