Re: [PATCH] kvm/stats: Update kvm stats to clear on write to their debugfs entry

["Radim Krčmář" <rkrcmar@redhat.com>]

2016-10-14 17:02+1100, Suraj Jitindar Singh:
> Various kvm vm and vcpu stats are provided via debugfs entries.
> Currently there is no way to reset these stats back to zero for the system
> except by stopping all vms.

It is not really resetting, just a special case of current behavior --
top-level stats are a sum of all existing VMs/VCPUs, so we would see 0
if they all had 0.

> Add the ability to clear (reset back to zero) these stats on a per stat
> basis by writing to the debugfs files.

I can see this being used before a test, but the userspace could also
read the value instead of writing and subtract it from the value after
the test to get a similar result.

The userspace-only solution is insufficient?

When and what do you zero?

>                                        The stats are just reset to zero
> irrespective of what is actually written to the file.

Sounds good.  Setting the val would be as simple, but there shouldn't be
a reason to and it is a debug interface, so we can change it anytime.

> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> ---

I have applied it to kvm/queue for the moment, thanks.