[linux-perf-users removed from Cc] 14.09.2010 15:02, Michael Tokarev wrote: > 14.09.2010 14:39, Avi Kivity wrote: >> On 09/14/2010 12:25 PM, Michael Tokarev wrote: >>> Not that it is much helpful either. lsof: >>> >>> qemu-syst 23203 mjt 0u CHR 136,9 0t0 12 /dev/pts/9 >>> qemu-syst 23203 mjt 1u CHR 136,9 0t0 12 /dev/pts/9 >>> qemu-syst 23203 mjt 2u CHR 136,9 0t0 12 /dev/pts/9 >>> qemu-syst 23203 mjt 3u CHR 10,232 0t0 4402 /dev/kvm >>> qemu-syst 23203 mjt 4u 0000 0,9 0 607 anon_inode >>> qemu-syst 23203 mjt 5r FIFO 0,8 0t0 8172675 pipe >>> qemu-syst 23203 mjt 6w FIFO 0,8 0t0 8172675 pipe >>> qemu-syst 23203 mjt 7u CHR 10,200 0t0 1228 /dev/net/tun >>> qemu-syst 23203 mjt 8u 0000 0,9 0 607 anon_inode >>> qemu-syst 23203 mjt 9u IPv4 8173217 0t0 TCP *:5900 (LISTEN) >>> qemu-syst 23203 mjt 10u 0000 0,9 0 607 anon_inode >>> qemu-syst 23203 mjt 11u 0000 0,9 0 607 anon_inode >>> qemu-syst 23203 mjt 12u 0000 0,9 0 607 anon_inode >> >>> So it is constantly poking fds# 11, 12, 10, 5& 6. >>> 5 and 6 are pipe (selfpipe?), >> >> signalfd emulation, used to deliver signals efficiently. Older glibc? > > [e]glibc-2.11. > > $ grep SIGNAL config-host.mak > CONFIG_SIGNALFD=y > > From strace of another run: > 24318 signalfd(-1, [BUS ALRM IO], 8) = 12 > (so one of the remaining fds is a signalfd :) > >>> and 10..12 are "anon inode". >> >> Those are likely eventfds. >> >>> Here's the command line again: >>> >>> qemu-system-x86_64 \ >>> -netdev type=tap,ifname=tap-kvm,id=x \ >>> -device virtio-net-pci,netdev=x \ >>> -monitor stdio \ >>> -boot n \ >>> -usbdevice tablet \ >>> -m 1G \ >>> -vnc :0 >>> >>> Yes, it does quite a lot of timer stuff... ;) >> >> So timers internal to usb. >> >> Please try (independently): >> >> - just -usb, without -usbdevice tablet > > No, that one works as expected - all quiet. > -usbdevice tablet is also quiet up until > guest loads usb host controller driver > (not particular usb device driver). > >> - instrument calls to qemu_mod_timer() in hw/usb-*hci.c. Looks like >> these are all 1kHz, but something else is clearly happening. Ok. There's nothing interesting going on there either, apparently. It is using hw/usb-uhci.c. I added a few prints() in there, but they're firing at the defined 1KHz frequency. Just for test, I lowered the frequency (FRAME_TIMER_FREQ) from 1000 to 500, and the load dropped to half, from 19% to 9..10%. Looking at what hw/usb-uhci.c:uhci_frame_timer() routine does, it is quite expected to have that many writes and reads and that many gettimers(). It is polling for events every 1/1000th of a second, instead of using some form of select(). I'll do some more tests -- after all I'm curious why winXP does not show this behavour. Thanks! /mjt -- 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
