mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-10-05 16:37:50 +00:00
Code Issues Releases Wiki Activity

perf tools: Update topdown documentation for Sapphire Rapids

Browse source 
Update Topdown extension on Sapphire Rapids and how to collect the L2
events.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/1612296553-21962-10-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Kan Liang 2021-02-02 12:09:13 -08:00 committed by Arnaldo Carvalho de Melo
parent 63e39aa6ae
commit 7d91e8181d
1 changed files with 74 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

78
tools/perf/Documentation/topdown.txt
View file

@ -121,7 +121,7 @@ to read slots and the topdown metrics at different points of the program:
#define RDPMC_METRIC (1 << 29) /* return metric counters */
#define FIXED_COUNTER_SLOTS 3
#define METRIC_COUNTER_TOPDOWN_L1 0
#define METRIC_COUNTER_TOPDOWN_L1_L2 0
static inline uint64_t read_slots(void)
{
@ -130,7 +130,7 @@ static inline uint64_t read_slots(void)
static inline uint64_t read_metrics(void)
{
return _rdpmc(RDPMC_METRIC | METRIC_COUNTER_TOPDOWN_L1);
return _rdpmc(RDPMC_METRIC | METRIC_COUNTER_TOPDOWN_L1_L2);
}
Then the program can be instrumented to read these metrics at different
@ -152,11 +152,21 @@ The binary ratios in the metric value can be converted to float ratios:
#define GET_METRIC(m, i) (((m) >> (i*8)) & 0xff)
/* L1 Topdown metric events */
#define TOPDOWN_RETIRING(val) ((float)GET_METRIC(val, 0) / 0xff)
#define TOPDOWN_BAD_SPEC(val) ((float)GET_METRIC(val, 1) / 0xff)
#define TOPDOWN_FE_BOUND(val) ((float)GET_METRIC(val, 2) / 0xff)
#define TOPDOWN_BE_BOUND(val) ((float)GET_METRIC(val, 3) / 0xff)
/*
* L2 Topdown metric events.
* Available on Sapphire Rapids and later platforms.
*/
#define TOPDOWN_HEAVY_OPS(val) ((float)GET_METRIC(val, 4) / 0xff)
#define TOPDOWN_BR_MISPREDICT(val) ((float)GET_METRIC(val, 5) / 0xff)
#define TOPDOWN_FETCH_LAT(val) ((float)GET_METRIC(val, 6) / 0xff)
#define TOPDOWN_MEM_BOUND(val) ((float)GET_METRIC(val, 7) / 0xff)
and then converted to percent for printing.
The ratios in the metric accumulate for the time when the counter
@ -190,8 +200,8 @@ for that time period.
fe_bound_slots = GET_METRIC(metric_b, 2) * slots_b - fe_bound_slots_a
be_bound_slots = GET_METRIC(metric_b, 3) * slots_b - be_bound_slots_a
Later the individual ratios for the measurement period can be recreated
from these counts.
Later the individual ratios of L1 metric events for the measurement period can
be recreated from these counts.
slots_delta = slots_b - slots_a
retiring_ratio = (float)retiring_slots / slots_delta
@ -205,6 +215,48 @@ from these counts.
fe_bound_ratio * 100.,
be_bound_ratio * 100.);
The individual ratios of L2 metric events for the measurement period can be
recreated from L1 and L2 metric counters. (Available on Sapphire Rapids and
later platforms)
# compute scaled metrics for measurement a
heavy_ops_slots_a = GET_METRIC(metric_a, 4) * slots_a
br_mispredict_slots_a = GET_METRIC(metric_a, 5) * slots_a
fetch_lat_slots_a = GET_METRIC(metric_a, 6) * slots_a
mem_bound_slots_a = GET_METRIC(metric_a, 7) * slots_a
# compute delta scaled metrics between b and a
heavy_ops_slots = GET_METRIC(metric_b, 4) * slots_b - heavy_ops_slots_a
br_mispredict_slots = GET_METRIC(metric_b, 5) * slots_b - br_mispredict_slots_a
fetch_lat_slots = GET_METRIC(metric_b, 6) * slots_b - fetch_lat_slots_a
mem_bound_slots = GET_METRIC(metric_b, 7) * slots_b - mem_bound_slots_a
slots_delta = slots_b - slots_a
heavy_ops_ratio = (float)heavy_ops_slots / slots_delta
light_ops_ratio = retiring_ratio - heavy_ops_ratio;
br_mispredict_ratio = (float)br_mispredict_slots / slots_delta
machine_clears_ratio = bad_spec_ratio - br_mispredict_ratio;
fetch_lat_ratio = (float)fetch_lat_slots / slots_delta
fetch_bw_ratio = fe_bound_ratio - fetch_lat_ratio;
mem_bound_ratio = (float)mem_bound_slots / slota_delta
core_bound_ratio = be_bound_ratio - mem_bound_ratio;
printf("Heavy Operations %.2f%% Light Operations %.2f%% "
"Branch Mispredict %.2f%% Machine Clears %.2f%% "
"Fetch Latency %.2f%% Fetch Bandwidth %.2f%% "
"Mem Bound %.2f%% Core Bound %.2f%%\n",
heavy_ops_ratio * 100.,
light_ops_ratio * 100.,
br_mispredict_ratio * 100.,
machine_clears_ratio * 100.,
fetch_lat_ratio * 100.,
fetch_bw_ratio * 100.,
mem_bound_ratio * 100.,
core_bound_ratio * 100.);
Resetting metrics counters
==========================
@ -248,6 +300,24 @@ a sampling read group. Since the SLOTS event must be the leader of a TopDown
group, the second event of the group is the sampling event.
For example, perf record -e '{slots, $sampling_event, topdown-retiring}:S'
Extension on Sapphire Rapids Server
===================================
The metrics counter is extended to support TMA method level 2 metrics.
The lower half of the register is the TMA level 1 metrics (legacy).
The upper half is also divided into four 8-bit fields for the new level 2
metrics. Four more TopDown metric events are exposed for the end-users,
topdown-heavy-ops, topdown-br-mispredict, topdown-fetch-lat and
topdown-mem-bound.
Each of the new level 2 metrics in the upper half is a subset of the
corresponding level 1 metric in the lower half. Software can deduce the
other four level 2 metrics by subtracting corresponding metrics as below.
Light_Operations = Retiring - Heavy_Operations
Machine_Clears = Bad_Speculation - Branch_Mispredicts
Fetch_Bandwidth = Frontend_Bound - Fetch_Latency
Core_Bound = Backend_Bound - Memory_Bound
[1] https://software.intel.com/en-us/top-down-microarchitecture-analysis-method-win
[2] https://github.com/andikleen/pmu-tools/wiki/toplev-manual