linux.git/arch/powerpc/kernel/perf_event.c, branch v3.0.14

powerpc/perf_event: Skip updating kernel counters if register value shrinks

2011-04-18T03:08:23+00:00

Because of speculative event roll back, it is possible for some event coutners
to decrease between reads on POWER7.  This causes a problem with the way that
counters are updated.  Delta calues are calculated in a 64 bit value and the
top 32 bits are masked.  If the register value has decreased, this leaves us
with a very large positive value added to the kernel counters.  This patch
protects against this by skipping the update if the delta would be negative.
This can lead to a lack of precision in the coutner values, but from my testing
the value is typcially fewer than 10 samples at a time.

Signed-off-by: Eric B Munson 
Cc: stable@kernel.org
Signed-off-by: Benjamin Herrenschmidt

Fix common misspellings

2011-03-31T14:26:23+00:00

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi

perf, powerpc: Handle events that raise an exception without overflowing

2011-03-16T13:04:13+00:00

Events on POWER7 can roll back if a speculative event doesn't
eventually complete. Unfortunately in some rare cases they will
raise a performance monitor exception. We need to catch this to
ensure we reset the PMC. In all cases the PMC will be 256 or less
cycles from overflow.

Signed-off-by: Anton Blanchard 
Signed-off-by: Peter Zijlstra 
Cc:  # as far back as it applies cleanly
LKML-Reference: <20110309143842.6c22845e@kryten>
Signed-off-by: Ingo Molnar

powerpc: perf: Fix frequency calculation for overflowing counters

2011-01-17T10:43:02+00:00

When profiling a benchmark that is almost 100% userspace, I noticed some wildly
inaccurate profiles that showed almost all time spent in the kernel.

Closer examination shows we were programming a tiny number of cycles into the
PMU after each overflow (about ~200 away from the next overflow). This gets us
stuck in a loop which we eventually break out of by throttling the PMU (there
are regular throttle/unthrottle events in the log).

It looks like we aren't setting event->hw.last_period to something same and the
frequency to period calculations in perf are going haywire.

With the following patch we find the correct period after a few interrupts and
stay there. I also see no more throttle events.

Signed-off-by: Anton Blanchard 
Acked-by: Benjamin Herrenschmidt 
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Paul Mackerras 
Cc: Peter Zijlstra 
Cc: Arnaldo Carvalho de Melo 
LKML-Reference: <20110117161742.5feb3761@kryten>
Signed-off-by: Ingo Molnar

perf: Dynamic pmu types

2010-12-16T10:36:43+00:00

Extend the perf_pmu_register() interface to allow for named and
dynamic pmu types.

Because we need to support the existing static types we cannot use
dynamic types for everything, hence provide a type argument.

If we want to enumerate the PMUs they need a name, provide one.

Signed-off-by: Peter Zijlstra 
LKML-Reference: <20101117222056.259707703@chello.nl>
Signed-off-by: Ingo Molnar

perf, powerpc: Fix power_pmu_event_init to not use event->ctx

2010-10-19T07:18:34+00:00

Commit c3f00c70 ("perf: Separate find_get_context() from event
initialization") changed the generic perf_event code to call
perf_event_alloc, which calls the arch-specific event_init code,
before looking up the context for the new event.  Unfortunately,
power_pmu_event_init uses event->ctx->task to see whether the
new event is a per-task event or a system-wide event, and thus
crashes since event->ctx is NULL at the point where
power_pmu_event_init gets called.

(The reason it needs to know whether it is a per-task event is
because there are some hardware events on Power systems which
only count when the processor is not idle, and there are some
fixed-function counters which count such events.  For example,
the "run cycles" event counts cycles when the processor is not
idle.  If the user asks to count cycles, we can use "run cycles"
if this is a per-task event, since the processor is running when
the task is running, by definition.  We can't use "run cycles"
if the user asks for "cycles" on a system-wide counter.)

Fortunately the information we need is in the
event->attach_state field, so we just use that instead.

Signed-off-by: Paul Mackerras 
Cc: Benjamin Herrenschmidt 
Cc: Peter Zijlstra 
Cc: Frederic Weisbecker 
LKML-Reference: <20101019055535.GA10398@drongo>
Signed-off-by: Ingo Molnar 
Reported-by: Alexey Kardashevskiy 
Signed-off-by: Ingo Molnar

perf: Rework the PMU methods

2010-09-09T18:46:30+00:00

Replace pmu::{enable,disable,start,stop,unthrottle} with
pmu::{add,del,start,stop}, all of which take a flags argument.

The new interface extends the capability to stop a counter while
keeping it scheduled on the PMU. We replace the throttled state with
the generic stopped state.

This also allows us to efficiently stop/start counters over certain
code paths (like IRQ handlers).

It also allows scheduling a counter without it starting, allowing for
a generic frozen state (useful for rotating stopped counters).

The stopped state is implemented in two different ways, depending on
how the architecture implemented the throttled state:

 1) We disable the counter:
    a) the pmu has per-counter enable bits, we flip that
    b) we program a NOP event, preserving the counter state

 2) We store the counter state and ignore all read/overflow events

Signed-off-by: Peter Zijlstra 
Cc: paulus 
Cc: stephane eranian 
Cc: Robert Richter 
Cc: Will Deacon 
Cc: Paul Mundt 
Cc: Frederic Weisbecker 
Cc: Cyrill Gorcunov 
Cc: Lin Ming 
Cc: Yanmin 
Cc: Deng-Cheng Zhu 
Cc: David Miller 
Cc: Michael Cree 
LKML-Reference: 
Signed-off-by: Ingo Molnar

perf: Per PMU disable

2010-09-09T18:46:29+00:00

Changes perf_disable() into perf_pmu_disable().

Signed-off-by: Peter Zijlstra 
Cc: paulus 
Cc: stephane eranian 
Cc: Robert Richter 
Cc: Will Deacon 
Cc: Paul Mundt 
Cc: Frederic Weisbecker 
Cc: Cyrill Gorcunov 
Cc: Lin Ming 
Cc: Yanmin 
Cc: Deng-Cheng Zhu 
Cc: David Miller 
Cc: Michael Cree 
LKML-Reference: 
Signed-off-by: Ingo Molnar

perf: Reduce perf_disable() usage

2010-09-09T18:46:29+00:00

Since the current perf_disable() usage is only an optimization,
remove it for now. This eases the removal of the __weak
hw_perf_enable() interface.

Signed-off-by: Peter Zijlstra 
Cc: paulus 
Cc: stephane eranian 
Cc: Robert Richter 
Cc: Will Deacon 
Cc: Paul Mundt 
Cc: Frederic Weisbecker 
Cc: Cyrill Gorcunov 
Cc: Lin Ming 
Cc: Yanmin 
Cc: Deng-Cheng Zhu 
Cc: David Miller 
Cc: Michael Cree 
LKML-Reference: 
Signed-off-by: Ingo Molnar

perf: Register PMU implementations

2010-09-09T18:46:28+00:00

Simple registration interface for struct pmu, this provides the
infrastructure for removing all the weak functions.

Signed-off-by: Peter Zijlstra 
Cc: paulus 
Cc: stephane eranian 
Cc: Robert Richter 
Cc: Will Deacon 
Cc: Paul Mundt 
Cc: Frederic Weisbecker 
Cc: Cyrill Gorcunov 
Cc: Lin Ming 
Cc: Yanmin 
Cc: Deng-Cheng Zhu 
Cc: David Miller 
Cc: Michael Cree 
LKML-Reference: 
Signed-off-by: Ingo Molnar