On Mon, 2008-01-21 at 12:50 +0200, Avi Kivity wrote: > Dor Laor wrote: > > On Mon, 2008-01-21 at 12:13 +0200, Avi Kivity wrote: > > > >> Jan Kiszka wrote: > >> > >>> Hi Avi, > >>> > >>> commit "kvm: qemu: consume all pending I/O in I/O loop" > >>> (8ab8bb09f1115b9bf733f885cc92b6c63d83f420) broke reading data bursts > >>> from serial devices (and maybe from other character devices as well) by > >>> guests. Reason: serial devices do input flow control via fd_read_poll, > >>> but qemu now ignores this fact by pushing all data into the virtual > >>> device as soon as it is available. > >>> > >>> Patch below is not really nice (just as the whole internal virtual I/O > >>> interface at the moment, IMHO), but it re-enables the serial ports for > >>> now. > >>> > >>> > >>> > >> I'm worried that it will break Dor's hack that speeds up virtio. Dor? > >> > >> > > > > It should be fine. Tap device without my hack has fd_read_poll null and > > I hacked it to have a handler that returns false if virtio is used and > > true otherwise. > > So Jan's patch should set 'more' to 1 and it will be like before. > > > > > > But if virtio is used with this patch, it won't set 'more' to 1. Will > virtio handle it or will throughput drop to be related to whatever > timers we have set up? >
Virtio+tap with the performance hack does it's own select on the related fd. Virtio+user will remain as before. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
