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perf/x86-ibs: Precise event sampling with IBS for AMD CPUs

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This patch adds support for precise event sampling with IBS. There are
two counting modes to count either cycles or micro-ops. If the
corresponding performance counter events (hw events) are setup with
the precise flag set, the request is redirected to the ibs pmu:

 perf record -a -e cpu-cycles:p ...    # use ibs op counting cycle count
 perf record -a -e r076:p ...          # same as -e cpu-cycles:p
 perf record -a -e r0C1:p ...          # use ibs op counting micro-ops

Each ibs sample contains a linear address that points to the
instruction that was causing the sample to trigger. With ibs we have
skid 0. Thus, ibs supports precise levels 1 and 2. Samples are marked
with the PERF_EFLAGS_EXACT flag set. In rare cases the rip is invalid
when IBS was not able to record the rip correctly. Then the
PERF_EFLAGS_EXACT flag is cleared and the rip is taken from pt_regs.

V2:
* don't drop samples in precise level 2 if rip is invalid, instead
  support the PERF_EFLAGS_EXACT flag

Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120502103309.GP18810@erda.amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Robert Richter 2012-03-12 12:54:32 +01:00 committed by Ingo Molnar
parent d47e8238cd
commit 450bbd493d
2 changed files with 76 additions and 4 deletions
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7
arch/x86/kernel/cpu/perf_event_amd.c
View file

@ -134,8 +134,13 @@ static u64 amd_pmu_event_map(int hw_event)
static int amd_pmu_hw_config(struct perf_event *event)
{
int ret = x86_pmu_hw_config(event);
int ret;
/* pass precise event sampling to ibs: */
if (event->attr.precise_ip && get_ibs_caps())
return -ENOENT;
ret = x86_pmu_hw_config(event);
if (ret)
return ret;

73
arch/x86/kernel/cpu/perf_event_amd_ibs.c
View file

@ -145,17 +145,80 @@ static struct perf_ibs *get_ibs_pmu(int type)
return NULL;
}
/*
* Use IBS for precise event sampling:
*
* perf record -a -e cpu-cycles:p ... # use ibs op counting cycle count
* perf record -a -e r076:p ... # same as -e cpu-cycles:p
* perf record -a -e r0C1:p ... # use ibs op counting micro-ops
*
* IbsOpCntCtl (bit 19) of IBS Execution Control Register (IbsOpCtl,
* MSRC001_1033) is used to select either cycle or micro-ops counting
* mode.
*
* The rip of IBS samples has skid 0. Thus, IBS supports precise
* levels 1 and 2 and the PERF_EFLAGS_EXACT is set. In rare cases the
* rip is invalid when IBS was not able to record the rip correctly.
* We clear PERF_EFLAGS_EXACT and take the rip from pt_regs then.
*
*/
static int perf_ibs_precise_event(struct perf_event *event, u64 *config)
{
switch (event->attr.precise_ip) {
case 0:
return -ENOENT;
case 1:
case 2:
break;
default:
return -EOPNOTSUPP;
}
switch (event->attr.type) {
case PERF_TYPE_HARDWARE:
switch (event->attr.config) {
case PERF_COUNT_HW_CPU_CYCLES:
*config = 0;
return 0;
}
break;
case PERF_TYPE_RAW:
switch (event->attr.config) {
case 0x0076:
*config = 0;
return 0;
case 0x00C1:
*config = IBS_OP_CNT_CTL;
return 0;
}
break;
default:
return -ENOENT;
}
return -EOPNOTSUPP;
}
static int perf_ibs_init(struct perf_event *event)
{
struct hw_perf_event *hwc = &event->hw;
struct perf_ibs *perf_ibs;
u64 max_cnt, config;
int ret;
perf_ibs = get_ibs_pmu(event->attr.type);
if (!perf_ibs)
if (perf_ibs) {
config = event->attr.config;
} else {
perf_ibs = &perf_ibs_op;
ret = perf_ibs_precise_event(event, &config);
if (ret)
return ret;
}
if (event->pmu != &perf_ibs->pmu)
return -ENOENT;
config = event->attr.config;
if (config & ~perf_ibs->config_mask)
return -EINVAL;
@ -437,8 +500,12 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
ibs_data.size = sizeof(u64) * size;
regs = *iregs;
if (!check_rip || !(ibs_data.regs[2] & IBS_RIP_INVALID))
if (check_rip && (ibs_data.regs[2] & IBS_RIP_INVALID)) {
regs.flags &= ~PERF_EFLAGS_EXACT;
} else {
instruction_pointer_set(&regs, ibs_data.regs[1]);
regs.flags |= PERF_EFLAGS_EXACT;
}
if (event->attr.sample_type & PERF_SAMPLE_RAW) {
raw.size = sizeof(u32) + ibs_data.size;