On 02/13/2017 01:49 AM, Nitesh Konkar wrote:
On Fri, Feb 10, 2017 at 3:22 AM, John Ferlan <jferlan@redhat.com <mailto:jferlan@redhat.com>> wrote:
On 01/27/2017 06:01 AM, Nitesh Konkar wrote: > This patch adds support and documentation > for the page_faults_maj perf event. > > Signed-off-by: Nitesh Konkar <nitkon12@linux.vnet.ibm.com <mailto:nitkon12@linux.vnet.ibm.com>> > --- > docs/formatdomain.html.in <http://formatdomain.html.in> | 7 +++++++ > docs/news.xml | 4 ++-- > docs/schemas/domaincommon.rng | 1 + > include/libvirt/libvirt-domain.h | 10 ++++++++++ > src/libvirt-domain.c | 3 +++ > src/qemu/qemu_driver.c | 1 + > src/util/virperf.c | 5 ++++- > src/util/virperf.h | 1 + > tests/genericxml2xmlindata/generic-perf.xml | 1 + > tools/virsh.pod | 5 +++++ > 10 files changed, 35 insertions(+), 3 deletions(-) >
NB: Similar comments from the page_faults_min...
> diff --git a/docs/formatdomain.html.in <http://formatdomain.html.in> b/docs/formatdomain.html.in <http://formatdomain.html.in> > index 1857168..50a6bdb 100644 > --- a/docs/formatdomain.html.in <http://formatdomain.html.in> > +++ b/docs/formatdomain.html.in <http://formatdomain.html.in> > @@ -1943,6 +1943,7 @@ > <event name='context_switches' enabled='no'/> > <event name='cpu_migrations' enabled='no'/> > <event name='page_faults_min' enabled='no'/> > + <event name='page_faults_maj' enabled='no'/> > </perf> > ... > </pre> > @@ -2052,6 +2053,12 @@ > platform</td> > <td><code>perf.page_faults_min</code></td> > </tr> > + <tr> > + <td><code>page_faults_maj</code></td> > + <td>the count of major page faults by applications running on the > + platform</td> > + <td><code>perf.page_faults_maj</code></td> > + </tr>
As already noted in patch 3... is maj+min the same as what patch 3 provides?
maj+min is not always exactly the same as page faults. Sometimes there is a small offset value.
Eg: perf record -a --event={page-faults,major-faults,minor-faults} 47 page-faults
0 major-faults
46 minor-faults Offset by 1
Eg: virsh domstats --perf Domain: 'Fedora' perf.page_faults=890 perf.page_faults_min=890 perf.page_faults_maj=0 Here maj+min=page_faults
Thus are all necessary?
I am not sure on this part. Probably yes as we dont want the user to add min+maj to get (approx)total page faults.
I don't mind all 3 being present... still if I'm going to ask the question, then someone getting the stats will ask the question... they may also wonder why maj+min != total. Perhaps something you could dig deeper on with the kernel code descriptions that are setting the value. My assumption is it's the "time" of the sample. That is a total page fault could have been counted even though it hadn't been counted as a maj or min page fault. John