[PATCH v3 04/15] perf/x86/amd: Support PERF_SAMPLE_{WEIGHT|WEIGHT_STRUCT}

Ravi Bangoria
2022-09-28T10:00:04Z

IbsDcMissLat indicates the number of clock cycles from when a miss is
detected in the data cache to when the data was delivered to the core.
Similarly, IbsTagToRetCtr provides number of cycles from when the op
was tagged to when the op was retired. Consider these fields for
sample->weight.

Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
---
Note:
While opening a new event, perf tool starts with a set of attributes
and goes on reverting some attributes in a predefined order until it
succeeds or run out or all attempts. Here, 1st attempt includes both
WEIGHT_STRUCT and exclude_guest which always fails because IBS does
not support guest filtering. The problem however is, perf reverts
WEIGHT_STRUCT but keeps trying with exclude_guest. Thus, although,
this patch enables WEIGHT_STRUCT support from kernel, using it from
the perf tool needs more changes(not included in this series).

arch/x86/events/amd/ibs.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index e20caa5cf02f..d883694e0fd4 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -955,6 +955,7 @@ static void perf_ibs_parse_ld_st_data(__u64 sample_type,
{
union ibs_op_data3 op_data3;
union ibs_op_data2 op_data2;
+ union ibs_op_data op_data;

data->data_src.val = PERF_MEM_NA;
op_data3.val = ibs_data->regs[ibs_op_msr_idx(MSR_AMD64_IBSOPDATA3)];
@@ -970,6 +971,19 @@ static void perf_ibs_parse_ld_st_data(__u64 sample_type,
perf_ibs_get_data_src(ibs_data, data, &op_data2, &op_data3);
data->sample_flags |= PERF_SAMPLE_DATA_SRC;
}
+
+ if (sample_type & PERF_SAMPLE_WEIGHT_TYPE && op_data3.dc_miss &&
+ data->data_src.mem_op == PERF_MEM_OP_LOAD) {
+ op_data.val = ibs_data->regs[ibs_op_msr_idx(MSR_AMD64_IBSOPDATA)];
+
+ if (sample_type & PERF_SAMPLE_WEIGHT_STRUCT) {
+ data->weight.var1_dw = op_data3.dc_miss_lat;
+ data->weight.var2_w = op_data.tag_to_ret_ctr;
+ } else if (sample_type & PERF_SAMPLE_WEIGHT) {
+ data->weight.full = op_data3.dc_miss_lat;
+ }
+ data->sample_flags |= PERF_SAMPLE_WEIGHT_TYPE;
+ }
}

static int perf_ibs_get_offset_max(struct perf_ibs *perf_ibs, u64 sample_type,
@@ -977,7 +991,8 @@ static int perf_ibs_get_offset_max(struct perf_ibs *perf_ibs, u64 sample_type,
{
if (sample_type & PERF_SAMPLE_RAW ||
(perf_ibs == &perf_ibs_op &&
- sample_type & PERF_SAMPLE_DATA_SRC))
+ (sample_type & PERF_SAMPLE_DATA_SRC ||
+ sample_type & PERF_SAMPLE_WEIGHT_TYPE)))
return perf_ibs->offset_max;
else if (check_rip)
return 3;
--
2.31.1