Ben
Will these two patches be pushed upstream or are they waiting for
review/test ?
They fix a hang that we get with some perf events.
Thanks,
Sukadev
Michael Neuling [mi...@neuling.org] wrote:
| If a PMC is about to overflow on a counter that's on an active perf event
| (ie. less than 256 from the end) and a _different_ PMC overflows just at this
| time (a PMC that's not on an active perf event), we currently mark the event
as
| found, but in reality it's not as it's likely the other PMC that caused the
| IRQ. Since we mark it as found the second catch all for overflows doesn't
run,
| and we don't reset the overflowing PMC ever. Hence we keep hitting that same
| PMC IRQ over and over and don't reset the actual overflowing counter.
|
| This is a rewrite of the perf interrupt handler for book3s to get around this.
| We now check to see if any of the PMCs have actually overflowed (ie >=
| 0x80000000). If yes, record it for active counters and just reset it for
| inactive counters. If it's not overflowed, then we check to see if it's one
of
| the buggy power7 counters and if it is, record it and continue. If none of
the
| PMCs match this, then we make note that we couldn't find the PMC that caused
| the IRQ.
|
| Signed-off-by: Michael Neuling <mi...@neuling.org>
| Reviewed-by: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com>
| cc: Paul Mackerras <pau...@samba.org>
| cc: Anton Blanchard <an...@samba.org>
| cc: Linux PPC dev <linuxppc-...@ozlabs.org>
| ---
| arch/powerpc/perf/core-book3s.c | 83
+++++++++++++++++++++++++--------------
| 1 file changed, 54 insertions(+), 29 deletions(-)
|
| diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
| index aa2465e..3575def 100644
| --- a/arch/powerpc/perf/core-book3s.c
| +++ b/arch/powerpc/perf/core-book3s.c
| @@ -1412,11 +1412,8 @@ unsigned long perf_instruction_pointer(struct pt_regs
*regs)
| return regs->nip;
| }
|
| -static bool pmc_overflow(unsigned long val)
| +static bool pmc_overflow_power7(unsigned long val)
| {
| - if ((int)val < 0)
| - return true;
| -
| /*
| * Events on POWER7 can roll back if a speculative event doesn't
| * eventually complete. Unfortunately in some rare cases they will
| @@ -1428,7 +1425,15 @@ static bool pmc_overflow(unsigned long val)
| * PMCs because a user might set a period of less than 256 and we
| * don't want to mistakenly reset them.
| */
| - if (pvr_version_is(PVR_POWER7) && ((0x80000000 - val) <= 256))
| + if ((0x80000000 - val) <= 256)
| + return true;
| +
| + return false;
| +}
| +
| +static bool pmc_overflow(unsigned long val)
| +{
| + if ((int)val < 0)
| return true;
|
| return false;
| @@ -1439,11 +1444,11 @@ static bool pmc_overflow(unsigned long val)
| */
| static void perf_event_interrupt(struct pt_regs *regs)
| {
| - int i;
| + int i, j;
| struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
| struct perf_event *event;
| - unsigned long val;
| - int found = 0;
| + unsigned long val[8];
| + int found, active;
| int nmi;
|
| if (cpuhw->n_limited)
| @@ -1458,33 +1463,53 @@ static void perf_event_interrupt(struct pt_regs *regs)
| else
| irq_enter();
|
| - for (i = 0; i < cpuhw->n_events; ++i) {
| - event = cpuhw->event[i];
| - if (!event->hw.idx || is_limited_pmc(event->hw.idx))
| + /* Read all the PMCs since we'll need them a bunch of times */
| + for (i = 0; i < ppmu->n_counter; ++i)
| + val[i] = read_pmc(i + 1);
| +
| + /* Try to find what caused the IRQ */
| + found = 0;
| + for (i = 0; i < ppmu->n_counter; ++i) {
| + if (!pmc_overflow(val[i]))
| continue;
| - val = read_pmc(event->hw.idx);
| - if ((int)val < 0) {
| - /* event has overflowed */
| - found = 1;
| - record_and_restart(event, val, regs);
| + if (is_limited_pmc(i + 1))
| + continue; /* these won't generate IRQs */
| + /*
| + * We've found one that's overflowed. For active
| + * counters we need to log this. For inactive
| + * counters, we need to reset it anyway
| + */
| + found = 1;
| + active = 0;
| + for (j = 0; j < cpuhw->n_events; ++j) {
| + event = cpuhw->event[j];
| + if (event->hw.idx == (i + 1)) {
| + active = 1;
| + record_and_restart(event, val[i], regs);
| + break;
| + }
| }
| + if (!active)
| + /* reset non active counters that have overflowed */
| + write_pmc(i + 1, 0);
| }
| -
| - /*
| - * In case we didn't find and reset the event that caused
| - * the interrupt, scan all events and reset any that are
| - * negative, to avoid getting continual interrupts.
| - * Any that we processed in the previous loop will not be negative.
| - */
| - if (!found) {
| - for (i = 0; i < ppmu->n_counter; ++i) {
| - if (is_limited_pmc(i + 1))
| + if (!found && pvr_version_is(PVR_POWER7)) {
| + /* check active counters for special buggy p7 overflow */
| + for (i = 0; i < cpuhw->n_events; ++i) {
| + event = cpuhw->event[i];
| + if (!event->hw.idx || is_limited_pmc(event->hw.idx))
| continue;
| - val = read_pmc(i + 1);
| - if (pmc_overflow(val))
| - write_pmc(i + 1, 0);
| + if (pmc_overflow_power7(val[event->hw.idx - 1])) {
| + /* event has overflowed in a buggy way*/
| + found = 1;
| + record_and_restart(event,
| + val[event->hw.idx - 1],
| + regs);
| + }
| }
| }
| + if (!found)
| + printk(KERN_WARNING "Can't find PMC that caused IRQ\n");
|
| /*
| * Reset MMCR0 to its normal value. This will set PMXE and
| --
| 1.7.9.5
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