[libvirt] [PATCH 7/9] perf: add page_faults_maj software perf event support

Nitesh Konkar niteshkonkar.libvirt at gmail.com
Mon Feb 13 06:49:38 UTC 2017


On Fri, Feb 10, 2017 at 3:22 AM, John Ferlan <jferlan at 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 at linux.vnet.ibm.com>
> > ---
> >  docs/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 b/docs/formatdomain.html.in
> > index 1857168..50a6bdb 100644
> > --- a/docs/formatdomain.html.in
> > +++ b/docs/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.


>
> >    </table>
> >
> >      <h3><a name="elementsDevices">Devices</a></h3>
> > diff --git a/docs/news.xml b/docs/news.xml
> > index 0e7c0d2..fe533f2 100644
> > --- a/docs/news.xml
> > +++ b/docs/news.xml
> > @@ -138,8 +138,8 @@
> >            executed, branch misses, bus cycles, stalled frontend
> >            cpu cycles, stalled backend cpu cycles, ref cpu cycles,
> >            cpu clock, task clock, page faults, context switches,
> > -          cpu migrations and page faults min by applications
> > -          running on the platform.
> > +          cpu migrations, page faults min and page faults maj by
> > +          applications running on the platform.
>
> Remove news.xml
>
> >          </description>
> >        </change>
> >        <change>
> > diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.
> rng
> > index f30ec0d..5f986d6 100644
> > --- a/docs/schemas/domaincommon.rng
> > +++ b/docs/schemas/domaincommon.rng
> > @@ -439,6 +439,7 @@
> >                <value>context_switches</value>
> >                <value>cpu_migrations</value>
> >                <value>page_faults_min</value>
> > +              <value>page_faults_maj</value>
> >              </choice>
> >            </attribute>
> >            <attribute name="enabled">
> > diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-
> domain.h
> > index 108591a..d16200f 100644
> > --- a/include/libvirt/libvirt-domain.h
> > +++ b/include/libvirt/libvirt-domain.h
> > @@ -2248,6 +2248,16 @@ void virDomainStatsRecordListFree(virDomainStatsRecordPtr
> *stats);
> >   */
> >  # define VIR_PERF_PARAM_PAGE_FAULTS_MIN  "page_faults_min"
> >
> > +/**
> > + * VIR_PERF_PARAM_PAGE_FAULTS_MAJ:
> > + *
> > + * Macro for typed parameter name that represents page_faults_maj
> > + * perf event which can be used to measure the count of major page
> > + * faults by applications running on the platform. It corresponds
> > + * to the "perf.page_faults_maj" field in the *Stats APIs.
> > + */
> > +# define VIR_PERF_PARAM_PAGE_FAULTS_MAJ  "page_faults_maj"
> > +
> >  int virDomainGetPerfEvents(virDomainPtr dom,
> >                             virTypedParameterPtr *params,
> >                             int *nparams,
> > diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
> > index 1be385e..1d7c181 100644
> > --- a/src/libvirt-domain.c
> > +++ b/src/libvirt-domain.c
> > @@ -11265,6 +11265,9 @@ virConnectGetDomainCapabilities(virConnectPtr
> conn,
> >   *     "perf.page_faults_min" - The count of minor page faults as
> unsigned long
> >   *                              long. It is produced by the
> page_faults_min
> >   *                              perf event.
> > + *     "perf.page_faults_maj" - The count of major page faults as
> unsigned long
> > + *                              long. It is produced by the
> page_faults_maj
> > + *                              perf event
> >   *
> >   * Note that entire stats groups or individual stat fields may be
> missing from
> >   * the output in case they are not supported by the given hypervisor,
> are not
> > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> > index 4f24fa6..c88bf5a 100644
> > --- a/src/qemu/qemu_driver.c
> > +++ b/src/qemu/qemu_driver.c
> > @@ -9555,6 +9555,7 @@ qemuDomainSetPerfEvents(virDomainPtr dom,
> >                                 VIR_PERF_PARAM_CONTEXT_SWITCHES,
> VIR_TYPED_PARAM_BOOLEAN,
> >                                 VIR_PERF_PARAM_CPU_MIGRATIONS,
> VIR_TYPED_PARAM_BOOLEAN,
> >                                 VIR_PERF_PARAM_PAGE_FAULTS_MIN,
> VIR_TYPED_PARAM_BOOLEAN,
> > +                               VIR_PERF_PARAM_PAGE_FAULTS_MAJ,
> VIR_TYPED_PARAM_BOOLEAN,
> >                                 NULL) < 0)
> >          return -1;
> >
> > diff --git a/src/util/virperf.c b/src/util/virperf.c
> > index c839b04..37f61e2 100644
> > --- a/src/util/virperf.c
> > +++ b/src/util/virperf.c
> > @@ -46,7 +46,7 @@ VIR_ENUM_IMPL(virPerfEvent, VIR_PERF_EVENT_LAST,
> >                "stalled_cycles_backend", "ref_cpu_cycles",
> >                "cpu_clock", "task_clock", "page_faults",
> >                "context_switches", "cpu_migrations",
> > -              "page_faults_min");
> > +              "page_faults_min", "page_faults_maj");
> >
> >  struct virPerfEvent {
> >      int type;
> > @@ -133,6 +133,9 @@ static struct virPerfEventAttr attrs[] = {
> >      {.type = VIR_PERF_EVENT_PAGE_FAULTS_MIN,
> >       .attrType = PERF_TYPE_SOFTWARE,
> >       .attrConfig = PERF_COUNT_SW_PAGE_FAULTS_MIN},
> > +    {.type = VIR_PERF_EVENT_PAGE_FAULTS_MAJ,
> > +     .attrType = PERF_TYPE_SOFTWARE,
> > +     .attrConfig = PERF_COUNT_SW_PAGE_FAULTS_MAJ},
> >  };
> >  typedef struct virPerfEventAttr *virPerfEventAttrPtr;
> >
> > diff --git a/src/util/virperf.h b/src/util/virperf.h
> > index aec352b..e99c870 100644
> > --- a/src/util/virperf.h
> > +++ b/src/util/virperf.h
> > @@ -53,6 +53,7 @@ typedef enum {
> >      VIR_PERF_EVENT_CONTEXT_SWITCHES,   /* Count of context switches */
> >      VIR_PERF_EVENT_CPU_MIGRATIONS,   /* Count of cpu migrations */
> >      VIR_PERF_EVENT_PAGE_FAULTS_MIN,   /* Count of minor page faults */
> > +    VIR_PERF_EVENT_PAGE_FAULTS_MAJ,   /* Count of major page faults */
> >
> >      VIR_PERF_EVENT_LAST
> >  } virPerfEventType;
> > diff --git a/tests/genericxml2xmlindata/generic-perf.xml
> b/tests/genericxml2xmlindata/generic-perf.xml
> > index 62ad973..a5b6dfb 100644
> > --- a/tests/genericxml2xmlindata/generic-perf.xml
> > +++ b/tests/genericxml2xmlindata/generic-perf.xml
> > @@ -32,6 +32,7 @@
> >      <event name='context_switches' enabled='yes'/>
> >      <event name='cpu_migrations' enabled='yes'/>
> >      <event name='page_faults_min' enabled='yes'/>
> > +    <event name='page_faults_maj' enabled='yes'/>
> >    </perf>
> >    <devices>
> >    </devices>
> > diff --git a/tools/virsh.pod b/tools/virsh.pod
> > index 4eb689e..d6bec4d 100644
> > --- a/tools/virsh.pod
> > +++ b/tools/virsh.pod
> > @@ -952,6 +952,7 @@ I<--perf> returns the statistics of all enabled perf
> events:
> >  "perf.context_switches" - the count of context switches
> >  "perf.cpu_migrations" - the count of cpu migrations
> >  "perf.page_faults_min" - the count of minor page faults
> > +"perf.page_faults_maj" - the count of major page faults
> >
> >  See the B<perf> command for more details about each event.
> >
> > @@ -2331,6 +2332,10 @@ B<Valid perf event names>
> >                      the page was present in the page cache, and
> therefore the
> >                      fault avoided loading it from storage, by
> applications
> >                      running on the platform
> > +  page_faults_maj - Provides the count of major page faults, that is,
> where
> > +                    the page was not present in the page cache, and
> therefore
> > +                    had to be fetched from storage, by applications
> > +                    running on the platform
>
> The min/maj descriptions here are a bit more wordy. It does help, but I
> wonder now is this the wrong place. That is should the longer
> description be in the API so that the rendered API docs get a nice long
> description and the virsh output remains somewhat terse.
>
> It really is up to you to decide, but I'm leaning towards better API doc
> descriptions...
>
Okay. Lets have a longer description in API and terse decription in virsh
output.

>
> John
> >
> >  B<Note>: The statistics can be retrieved using the B<domstats> command
> using
> >  the I<--perf> flag.
> >
>

Thanks for all the review comments.
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