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Optimizations to the way hwpmc gathers user callchains

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Changes to the code to gather user stacks:
* Delay setting pmc_cpumask until we actually have the stack.
* When recording user stack traces, only walk the portion of the ring
  that should have samples for us.

Sponsored by:	Juniper Networks
Approved by:	gnn (mentor)
MFC after:	1 month
This commit is contained in:
Jonathan T. Looney 2015-11-14 01:45:55 +00:00
parent f2307a2a25
commit c66ea2ee5c
1 changed files with 20 additions and 9 deletions
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29
sys/dev/hwpmc/hwpmc_mod.c
View file

@ -4096,6 +4096,7 @@ pmc_process_interrupt(int cpu, int ring, struct pmc *pm, struct trapframe *tf,
cpu, pm, (void *) tf, inuserspace,
(int) (psb->ps_write - psb->ps_samples),
(int) (psb->ps_read - psb->ps_samples));
callchaindepth = 1;
error = ENOMEM;
goto done;
}
@ -4153,7 +4154,8 @@ pmc_process_interrupt(int cpu, int ring, struct pmc *pm, struct trapframe *tf,
done:
/* mark CPU as needing processing */
CPU_SET_ATOMIC(cpu, &pmc_cpumask);
if (callchaindepth != PMC_SAMPLE_INUSE)
CPU_SET_ATOMIC(cpu, &pmc_cpumask);
return (error);
}
@ -4167,10 +4169,9 @@ pmc_process_interrupt(int cpu, int ring, struct pmc *pm, struct trapframe *tf,
static void
pmc_capture_user_callchain(int cpu, int ring, struct trapframe *tf)
{
int i;
struct pmc *pm;
struct thread *td;
struct pmc_sample *ps;
struct pmc_sample *ps, *ps_end;
struct pmc_samplebuffer *psb;
#ifdef INVARIANTS
int ncallchains;
@ -4189,15 +4190,17 @@ pmc_capture_user_callchain(int cpu, int ring, struct trapframe *tf)
/*
* Iterate through all deferred callchain requests.
* Walk from the current read pointer to the current
* write pointer.
*/
ps = psb->ps_samples;
for (i = 0; i < pmc_nsamples; i++, ps++) {
ps = psb->ps_read;
ps_end = psb->ps_write;
do {
if (ps->ps_nsamples != PMC_SAMPLE_INUSE)
continue;
goto next;
if (ps->ps_td != td)
continue;
goto next;
KASSERT(ps->ps_cpu == cpu,
("[pmc,%d] cpu mismatch ps_cpu=%d pcpu=%d", __LINE__,
@ -4222,7 +4225,12 @@ pmc_capture_user_callchain(int cpu, int ring, struct trapframe *tf)
#ifdef INVARIANTS
ncallchains++;
#endif
}
next:
/* increment the pointer, modulo sample ring size */
if (++ps == psb->ps_fence)
ps = psb->ps_samples;
} while (ps != ps_end);
KASSERT(ncallchains > 0,
("[pmc,%d] cpu %d didn't find a sample to collect", __LINE__,
@ -4232,6 +4240,9 @@ pmc_capture_user_callchain(int cpu, int ring, struct trapframe *tf)
("[pmc,%d] invalid td_pinned value", __LINE__));
sched_unpin(); /* Can migrate safely now. */
/* mark CPU as needing processing */
CPU_SET_ATOMIC(cpu, &pmc_cpumask);
return;
}