On (Wed) Apr 07 2010 [16:32:04], Alexander Graf wrote: > Amit Shah wrote: > > On (Thu) Apr 01 2010 [18:42:38], Alexander Graf wrote: > > > >> Virtio-Console can only process one character at a time. > >> > > > > The host can process as many as you give it, depending on the buffer > > size exposed by the guest. > > > > On older guests (guest kernels w/o multiport support), the guest reads > > input from host, processes it and only then opens up another buffer for > > the host to write into. > > > > On newer guests (guest kernels that support multiport), the guest > > fills the entire vq so that host can send as many buffers as possible > > without getting throttled. I guess you're getting hit by this. > > > > Probably, yes. > > >> Using it on S390 > >> gave me strage "lags" where I got the character I pressed before when > >> pressing one. So I typed in "abc" and only received "a", then pressed "d" > >> but the guest received "b" and so on. > >> > > > > This might be because qemu-char would not be able to send out 'b' while > > the guest still processes 'a' and has no free buffers to write out to. > > On seeing 'd', it flushes its queue. > > > > Can you try using a 2.6.34-rc3 kernel without this patch to see if > > things work fine? > > > > Hrm - would it actually matter? We need to have older guest kernels > working anyways. And my S390 LPAR doesn't exactly have a lot of disk > space, so compiling a kernel is anything but fun :-).
Oh I just want to find out if it works for you -- you shouldn't get hit by the 1-char limit anymore. Amit -- http://log.amitshah.net/