On 8/22/07, Avi Kivity <[EMAIL PROTECTED]> wrote: > Luca wrote: > >>> This is QEMU, with dynticks and HPET: > >>> > >>> % time seconds usecs/call calls errors syscall > >>> ------ ----------- ----------- --------- --------- ---------------- > >>> 52.10 0.002966 0 96840 clock_gettime > >>> 19.50 0.001110 0 37050 timer_gettime > >>> 10.66 0.000607 0 20086 timer_settime > >>> 10.40 0.000592 0 8985 2539 sigreturn > >>> 4.94 0.000281 0 8361 2485 select > >>> 2.41 0.000137 0 8362 gettimeofday > >>> ------ ----------- ----------- --------- --------- ---------------- > >>> 100.00 0.005693 179684 5024 total > >>> > >>> > >> This looks like 250 Hz? > >> > > > > Nope: > > > > # CONFIG_NO_HZ is not set > > # CONFIG_HZ_100 is not set > > # CONFIG_HZ_250 is not set > > # CONFIG_HZ_300 is not set > > CONFIG_HZ_1000=y > > CONFIG_HZ=1000 > > > > and I'm reading it from /proc/config.gz on the guest. > > > > Yeah, thought so -- so dyntick is broken at present.
I see a lot of sub ms timer_settime(). Many of them are the result of ->expire_time being less than the current qemu_get_clock(). This results into 250us timer due to MIN_TIMER_REARM_US; this happens only for the REALTIME timer. Other sub-ms timers are generated by the VIRTUAL timer. This first issue is easily fixed; if expire_time < current time then the timer has expired and hasn't been reprogrammed (and thus can be ignored). VIRTUAL just becomes more accurate with dyntics, before multiple timers were batched together. > Or maybe your host kernel can't support such a high rate. I don't know... a simple printf tells me that the signal handler is called about 1050 times per second, which sounds about right. Luca
