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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>
This commit is contained in:
Wei Huang 2015-01-23 15:56:04 -05:00 committed by Paolo Bonzini
parent 13704e4c45
commit fc116efad0
1 changed files with 5 additions and 0 deletions
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5
scripts/kvm/kvm_stat
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@ -186,6 +186,7 @@ ioctl_numbers = {
'SET_FILTER' : 0x40082406, 'SET_FILTER' : 0x40082406,
'ENABLE' : 0x00002400, 'ENABLE' : 0x00002400,
'DISABLE' : 0x00002401, 'DISABLE' : 0x00002401,
'RESET' : 0x00002403,
} }
def x86_init(flag): def x86_init(flag):
@ -346,6 +347,9 @@ class Event(object):
def disable(self): def disable(self):
import fcntl import fcntl
fcntl.ioctl(self.fd, ioctl_numbers['DISABLE'], 0) fcntl.ioctl(self.fd, ioctl_numbers['DISABLE'], 0)
def reset(self):
import fcntl
fcntl.ioctl(self.fd, ioctl_numbers['RESET'], 0)
class TracepointProvider(object): class TracepointProvider(object):
def __init__(self): def __init__(self):
@ -405,6 +409,7 @@ class TracepointProvider(object):
for group in self.group_leaders: for group in self.group_leaders:
for event in group.events: for event in group.events:
if event.name in fields: if event.name in fields:
event.reset()
event.enable() event.enable()
else: else:
event.disable() event.disable()