Commit fc116efa authored Jan 23, 2015 by Wei Huang Committed by Paolo Bonzini Jan 26, 2015

kvm_stat: Add RESET support for perf event ioctl



While running kvm_stat using tracepoint on ARM64 hardware (e.g. "kvm_stat
-1 -t"), the initial values of some kvm_userspace_exit counters were found
to be very suspecious. For instance the tracing tool showed that S390_TSCH
was called many times on ARM64 machine, which apparently was wrong.

This patch adds RESET ioctl support for perf monitoring. Before calling
ioctl to enable a perf event, this patch resets the counter first. With
this patch, the init counter values become correct on ARM64 hardware.

Example:

==== before patch ====
kvm_userspace_exit(S390_SIEIC)      1426         0
kvm_userspace_exit(S390_TSCH)       339         0

==== after patch ====
kvm_userspace_exit(S390_SIEIC)         0         0
kvm_userspace_exit(S390_TSCH)         0         0

Signed-off-by: Wei Huang <wei@redhat.com>

parent 13704e4c

scripts/kvm/kvm_stat

+5 −0

Original line number	Diff line number	Diff line
		@@ -186,6 +186,7 @@ ioctl_numbers = {
		'SET_FILTER' : 0x40082406,
		'ENABLE' : 0x00002400,
		'DISABLE' : 0x00002401,
		'RESET' : 0x00002403,
		}

		def x86_init(flag):
		@@ -346,6 +347,9 @@ class Event(object):
		def disable(self):
		import fcntl
		fcntl.ioctl(self.fd, ioctl_numbers['DISABLE'], 0)
		def reset(self):
		import fcntl
		fcntl.ioctl(self.fd, ioctl_numbers['RESET'], 0)

		class TracepointProvider(object):
		def __init__(self):
		@@ -405,6 +409,7 @@ class TracepointProvider(object):
		for group in self.group_leaders:
		for event in group.events:
		if event.name in fields:
		event.reset()
		event.enable()
		else:
		event.disable()