On Wed, Aug 31, 2016 at 12:05:14PM -0700, Vineet Gupta wrote:

On 08/26/2016 10:31 AM, Vineet Gupta wrote:

quoted

On 08/25/2016 04:49 AM, Alexey Brodkin wrote:

quoted

...
 	[PERF_COUNT_ARC_EDTLB] = "edtlb",	/* D-TLB Miss */
 	[PERF_COUNT_ARC_EITLB] = "eitlb",	/* I-TLB Miss */
+
+	[PERF_COUNT_HW_CACHE_REFERENCES] = "imemrdc",	/* Instr: mem read cached */
+	[PERF_COUNT_HW_CACHE_MISSES] = "dclm",		/* D-cache Load Miss */

I think this is duplicating a mistake we already have. I vaguely remember when
doing some hackbench profiling last year with range based profiling confined to
memset routine and saw that L1-dcache-misses was counting zero. This is because it
only counts LD misses while memset only does ST.

Performance counter stats for '/sbin/hackbench':

     0 L1-dcache-misses
     0 L1-dcache-load-misses
     1846082 L1-dcache-store-misses


@PeterZ do you concur that is wrong and we ought to setup 2 counters to do this
correctly ?

Hi Peter / Will,

Can you provide some guidance here. So I looked at what others do -
ARMV7_PERFCTR_L1_DCACHE_REFILL counts both load and store misses, while ARC has 2
separate conditions for load or stores. Is there an existing mechanism to "group"
/ "add" them to give a cumulative PERF_COUNT_HW_CACHE_MISSES 

Nope. So I would not try and use these generic events. In other news, it
seems like there's finally some progress on the JSON patches:

  https://lkml.kernel.org/r/20160831114254.GA9001@krava

Which would make using non-standard events easier.

- is that what perf event grouping is ?

Again, nope. Perf event groups are single counter (so no implicit
addition) that are co-scheduled on the PMU.

Quoting from perf wiki @ https://perf.wiki.kernel.org/index.php/Tutorial

"It can be interesting to try and pack events in a way that guarantees that event
A and B are always measured together. Although the perf_events kernel interface
provides support for event grouping, the current perf tool does *not*."

That seems out-dated, Jiri added grouping support to perf-tool quite a
while back.

You can do it like:

	perf stat -e '{cycles,instructions}'

Which will place the cycles event and the instructions event in a group
and thereby guarantee they're co-scheduled.