[Qemu-devel] errno 13, fopen qemu trace file.

[Nir Levy]

Hello everybody,

I have a progress in tracing qemu,
I add the thread and tag done for each kvm_ioctl, kvm_vm_ioctl, kvm_vcpu_ioctl
in purpose of investigating pure hypervisor activity and delays on host.
the kvm type print only for convenience.

for example:
kvm_ioctl 3106435.230545 pid=11347 thread=11347 type=0xae03 arg=0x25
kvm_ioctl_done 3106435.230546 pid=11347 thread=11347 type=0xae03 arg=0x25 
diff=1 (KVM_CHECK_EXTENSION)
kvm_vcpu_ioctl 3106435.253930 pid=11347 thread=11354 cpu_index=0x2 
type=0x4008ae9c arg=0x56417e6cb4f0
kvm_vcpu_ioctl_done 3106435.253931 pid=11347 thread=11354 cpu_index=0x2 
type=0x4008ae9c arg=0x56417e6cb4f0 diff=1 (KVM_X86_SETUP_MCE)

kvm_vm_ioctl 3106435.268896 pid=11347 thread=11347 type=0x4020ae46 
arg=0x7ffed97cf9d0
kvm_vm_ioctl_done 3106435.269082 pid=11347 thread=11347 type=0x4020ae46 
arg=0x7ffed97cf9d0 diff=186 (KVM_SET_USER_MEMORY_REGION)

I have notice KVM_RUN can take even seconds but that is probably low priority 
tasks,(io workers probably)
but this 186micro second on the main qemu thread is suspicious and might cause 
application running over vm delays.

however when I have switch back to installed libvirtd 1.2.13.2
( my version has extended timeout for qemu debugging - ver 1.2.21)


void st_set_trace_file_enabled(bool enable)
{
        ...
        trace_fp = fopen(trace_file_name, "wb");

trace_fp returns null and errno is 13 access denied.
In my installation I did not create cgroup,

If you have some hint for this issue it will be great.
regards.
Nir Levy
SW Engineer


Nir Levy
SW Engineer

Web: www.asocstech.com<http://www.asocstech.com/> |
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