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[v3,00/12] perf/core: Generalise event exclusion checking

Message ID 1544114849-47266-1-git-send-email-andrew.murray@arm.com
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Series perf/core: Generalise event exclusion checking | expand

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Andrew Murray Dec. 6, 2018, 4:47 p.m. UTC
Many PMU drivers do not have the capability to exclude counting events
that occur in specific contexts such as idle, kernel, guest, etc. These
drivers indicate this by returning an error in their event_init upon
testing the events attribute flags.

However this approach requires that each time a new event modifier is
added to perf, all the perf drivers need to be modified to indicate that
they don't support the attribute. This results in additional boiler-plate
code common to many drivers that needs to be maintained. Furthermore the
drivers are not consistent with regards to the error value they return
when reporting unsupported attributes.

This patchset allow PMU drivers to advertise their inability to exclude
based on context via a new capability: PERF_PMU_CAP_NO_EXCLUDE. This
allows the perf core to reject requests for exclusion events where there
is no support in the PMU.

This is a functional change, in particular:

 - Some drivers will now additionally (but correctly) report unsupported
   exclusion flags. It's typical for existing userspace tools such as
   perf to handle such errors by retrying the system call without the
   unsupported flags.

 - Drivers that do not support any exclusion that previously reported
   -EPERM or -EOPNOTSUPP will now report -EINVAL - this is consistent
   with the majority and results in userspace perf retrying without
   exclusion.

All drivers touched by this patchset have been compile tested.

Changes from v2:

 - Invert logic from CAP_EXCLUDE to CAP_NO_EXCLUDE

Changes from v1:

 - Changed approach from explicitly rejecting events in unsupporting PMU
   drivers to explicitly advertising a capability in PMU drivers that
   do support exclusion events

 - Added additional information to tools/perf/design.txt

 - Rename event_has_exclude_flags to event_has_any_exclude_flag and
   update commit log to reflect it's a function

Andrew Murray (12):
  perf/doc: update design.txt for exclude_{host|guest} flags
  perf/core: add function to test for event exclusion flags
  perf/core: add PERF_PMU_CAP_NO_EXCLUDE for exclusion incapable PMUs
  alpha: perf/core: use PERF_PMU_CAP_NO_EXCLUDE
  arm: perf: conditionally use PERF_PMU_CAP_NO_EXCLUDE
  arm: perf/core: use PERF_PMU_CAP_NO_EXCLUDE for exclude incapable PMUs
  drivers/perf: perf/core: use PERF_PMU_CAP_NO_EXCLUDE for exclude
    incapable PMUs
  drivers/perf: perf/core: use PERF_PMU_CAP_NO_EXCLUDE for exclude
    incapable PMUs
  powerpc: perf/core: use PERF_PMU_CAP_NO_EXCLUDE for exclude incapable
    PMUs
  x86: perf/core: use PERF_PMU_CAP_NO_EXCLUDE for exclude incapable PMUs
  x86: perf/core: use PERF_PMU_CAP_NO_EXCLUDE for exclude incapable PMUs
  perf/core: remove unused perf_flags

 arch/alpha/kernel/perf_event.c                |  7 +------
 arch/arm/mach-imx/mmdc.c                      |  9 ++-------
 arch/arm/mm/cache-l2x0-pmu.c                  |  9 +--------
 arch/powerpc/perf/hv-24x7.c                   | 10 +---------
 arch/powerpc/perf/hv-gpci.c                   | 10 +---------
 arch/powerpc/perf/imc-pmu.c                   | 19 +------------------
 arch/x86/events/amd/ibs.c                     | 13 +------------
 arch/x86/events/amd/iommu.c                   |  6 +-----
 arch/x86/events/amd/power.c                   | 10 ++--------
 arch/x86/events/amd/uncore.c                  |  7 ++-----
 arch/x86/events/intel/cstate.c                | 12 +++---------
 arch/x86/events/intel/rapl.c                  |  9 ++-------
 arch/x86/events/intel/uncore.c                |  9 +--------
 arch/x86/events/intel/uncore_snb.c            |  9 ++-------
 arch/x86/events/msr.c                         | 10 ++--------
 drivers/perf/arm-cci.c                        | 10 +---------
 drivers/perf/arm-ccn.c                        |  6 ++----
 drivers/perf/arm_dsu_pmu.c                    |  9 ++-------
 drivers/perf/arm_pmu.c                        | 15 +++++----------
 drivers/perf/hisilicon/hisi_uncore_ddrc_pmu.c |  1 +
 drivers/perf/hisilicon/hisi_uncore_hha_pmu.c  |  1 +
 drivers/perf/hisilicon/hisi_uncore_l3c_pmu.c  |  1 +
 drivers/perf/hisilicon/hisi_uncore_pmu.c      |  9 ---------
 drivers/perf/qcom_l2_pmu.c                    |  9 +--------
 drivers/perf/qcom_l3_pmu.c                    |  8 +-------
 drivers/perf/xgene_pmu.c                      |  6 +-----
 include/linux/perf_event.h                    | 10 ++++++++++
 include/uapi/linux/perf_event.h               |  2 --
 kernel/events/core.c                          |  9 +++++++++
 tools/include/uapi/linux/perf_event.h         |  2 --
 tools/perf/design.txt                         |  4 ++++
 31 files changed, 62 insertions(+), 189 deletions(-)

Comments

Will Deacon Dec. 7, 2018, 5:25 p.m. UTC | #1
On Thu, Dec 06, 2018 at 04:47:17PM +0000, Andrew Murray wrote:
> Many PMU drivers do not have the capability to exclude counting events
> that occur in specific contexts such as idle, kernel, guest, etc. These
> drivers indicate this by returning an error in their event_init upon
> testing the events attribute flags.
> 
> However this approach requires that each time a new event modifier is
> added to perf, all the perf drivers need to be modified to indicate that
> they don't support the attribute. This results in additional boiler-plate
> code common to many drivers that needs to be maintained. Furthermore the
> drivers are not consistent with regards to the error value they return
> when reporting unsupported attributes.
> 
> This patchset allow PMU drivers to advertise their inability to exclude
> based on context via a new capability: PERF_PMU_CAP_NO_EXCLUDE. This
> allows the perf core to reject requests for exclusion events where there
> is no support in the PMU.
> 
> This is a functional change, in particular:
> 
>  - Some drivers will now additionally (but correctly) report unsupported
>    exclusion flags. It's typical for existing userspace tools such as
>    perf to handle such errors by retrying the system call without the
>    unsupported flags.
> 
>  - Drivers that do not support any exclusion that previously reported
>    -EPERM or -EOPNOTSUPP will now report -EINVAL - this is consistent
>    with the majority and results in userspace perf retrying without
>    exclusion.
> 
> All drivers touched by this patchset have been compile tested.

For the bits under arch/arm/ and drivers/perf:

Acked-by: Will Deacon <will.deacon@arm.com>

Note that I've queued the TX2 uncore PMU for 4.21 [1], which could also
benefit from your new flag.

Will

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/commit/?h=for-next/perf&id=69c32972d59388c041268e8206e8eb1acff29b9a
Andrew Murray Dec. 10, 2018, 11:51 p.m. UTC | #2
On Fri, Dec 07, 2018 at 05:25:17PM +0000, Will Deacon wrote:
> On Thu, Dec 06, 2018 at 04:47:17PM +0000, Andrew Murray wrote:
> > Many PMU drivers do not have the capability to exclude counting events
> > that occur in specific contexts such as idle, kernel, guest, etc. These
> > drivers indicate this by returning an error in their event_init upon
> > testing the events attribute flags.
> > 
> > However this approach requires that each time a new event modifier is
> > added to perf, all the perf drivers need to be modified to indicate that
> > they don't support the attribute. This results in additional boiler-plate
> > code common to many drivers that needs to be maintained. Furthermore the
> > drivers are not consistent with regards to the error value they return
> > when reporting unsupported attributes.
> > 
> > This patchset allow PMU drivers to advertise their inability to exclude
> > based on context via a new capability: PERF_PMU_CAP_NO_EXCLUDE. This
> > allows the perf core to reject requests for exclusion events where there
> > is no support in the PMU.
> > 
> > This is a functional change, in particular:
> > 
> >  - Some drivers will now additionally (but correctly) report unsupported
> >    exclusion flags. It's typical for existing userspace tools such as
> >    perf to handle such errors by retrying the system call without the
> >    unsupported flags.
> > 
> >  - Drivers that do not support any exclusion that previously reported
> >    -EPERM or -EOPNOTSUPP will now report -EINVAL - this is consistent
> >    with the majority and results in userspace perf retrying without
> >    exclusion.
> > 
> > All drivers touched by this patchset have been compile tested.
> 
> For the bits under arch/arm/ and drivers/perf:
> 
> Acked-by: Will Deacon <will.deacon@arm.com>
> 
> Note that I've queued the TX2 uncore PMU for 4.21 [1], which could also
> benefit from your new flag.

Ah thanks for pointing this out, I'll send a patch in due course.

Thanks,

Andrwe Murray

> 
> Will
> 
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/commit/?h=for-next/perf&id=69c32972d59388c041268e8206e8eb1acff29b9a