On 13/10/15 14:30, Martin Lucina wrote:
Hi,
I've just merged support for using the KVM paravirtualized clock for
timekeeping. The main user-visible change is that when booting hw on KVM,
the 0.1s delay to calibrate the TSC is no longer required.
For diagnostic purposes, the clock code will print a message at boot
indicating which clock is being used (PV clock or plain TSC).
Thanks, I can observe the difference even with human eye -- with the old
clock code there's a noticeable "jerk" in the boot output (I assume
between "rumprun bare metal bootstrap" and "clock init", though
admittedly I can't read the text, just observe the jerk). With pvclock
everything just blurts out.
It takes ~30ms to boot from clock init to main() on my core2 laptop (*).
Newer CPUs should perform a lot better there. However, it still takes
ages (.5s) from the launch of qemu to the bmk entrypoint, so we need to
get that figure down somehow. The developing fastboot story is here:
https://github.com/rumpkernel/rumprun/issues/54
*) boot messages ("dmesg") cost 10ms more -- turning the messages on and
off is yet another reason we need a bootstrap config string.
