Re: perf: Add support for full Intel event lists v7

From: Sukadev Bhattiprolu
Date: Tue Jul 08 2014 - 14:44:10 EST

Andi Kleen [andi@xxxxxxxxxxxxxx] wrote:
| Should be ready for merge now. Please consider.

Overall I think it is a cool feature. I was able to run some simple
tests on Power8 (by explicitly specifying the JSON file). Have a couple
of questions below.

| [v2: Review feedback addressed and some minor improvements]
| [v3: More review feedback addressed and handle test failures better.
| Ported to latest tip/core.]
| [v4: Addressed Namhyung's feedback]
| [v5: Rebase to latest tree. Minor description update.]
| [v6: Rebase. Add acked by from Namhyung and address feedback. Some minor
| fixes. Should be good to go now I hope. The period patch was dropped,
| as that is already handled. I added an extra patch for a --quiet argument
| for perf list]
| [v7: Just rebase to latest tip/core. Should be ready to merge.]
| perf has high level events which are useful in many cases. However
| there are some tuning situations where low level events in the CPU
| are needed. Traditionally this required specifying the event in
| raw form (very awkward) or using non standard frontends
| like ocperf or patching in libpfm.
| Intel CPUs can have very large event files (Haswell has ~336 core events,
| much more if you add uncore or all the offcore combinations), which is too
| large to describe through the kernel interface. It would require tying up
| significant amounts of unswappable memory for this.
| oprofile always had separate event list files that were maintained by
| the CPU vendors. The oprofile events were shipped with the tool.
| The Intel events get updated regularly, for example to add references
| to the specification updates or add new events.
| Unfortunately oprofile usually did not keep up with these updates,
| so the events in oprofile were often out of date. In addition
| it ties up quite a bit of disk space, mostly for CPUs you don't have.
| This patch kit implements another mechanism that avoids these problems.
| Intel releases the event lists for CPUs in a standardized JSON format
| on a download server.
| I implemented an automatic downloader to get the event file for the
| current CPU. The events are stored in ~/.cache/pmu-events.
| Then perf adds a parser that converts the JSON format into perf event
| aliases, which then can be used directly as any other perf event.
| The parsing is done using a simple existing JSON library.
| The events are still abstracted for perf, but the abstraction mechanism is
| through the downloaded file instead of through the kernel.
| The JSON format and perf parser has some minor Intelisms, but they
| are simple and small and optional. It's easy to extend, so it would be
| possible to use it for other CPUs too, add different pmu attributes, and
| add new download sites to the downloader tool.

Is there a minimal set of JSON entries an architecture would need ?

I tried the following on Power
"EventCode": "2",
"EventName": "PM_INST_CMPL",
"BriefDescription": "Instructions completed",
"PublicDescription": "Number of PPC instructions finished",
"EventCode": "0x1E",
"EventName": "PM_CYC",
"BriefDescription": "Cycles completed",
"PublicDescription": "Number of PPC cycles finished",

/tmp/perf record --events-file=/tmp/power8.json -e PM_INST_CMPL sleep 1

works, but for some TBD reason,

/tmp/perf list --events-file=/tmp/power8.json doesn't list PM_INST_CMPL.

Another observation was that the order of --events-file and -e is significant.
Maybe worth a note in the man page.

| Currently only core events are supported, uncore may come at a later
| point. No kernel changes, all code in perf user tools only.
| Some of the parser files are partially shared with separate event parser
| library and are thus 2-clause BSD licensed.
| Patches also available from
| git:// perf/json
| Example output:
| % perf download
| Downloading models file
| Downloading readme.txt
| 2014-03-05 10:39:33 URL: [10320/10320] -> "readme.txt" [1]
| 2014-03-05 10:39:34 URL: [1207/1207] -> "mapfile.csv" [1]
| Downloading events file
| % perf list
| ...
| br_inst_exec.all_branches [Speculative and retired
| branches]
| br_inst_exec.all_conditional [Speculative and retired
| macro-conditional
| branches]
| br_inst_exec.all_direct_jmp [Speculative and retired
| macro-unconditional
| branches excluding
| calls and indirects]
| ... 333 more new events ...
| % perf stat -e br_inst_exec.all_direct_jmp true

Can you specify the qualifiers like ':k' or ':ku' with the events on Intel ?
to only monitor kernel or user ? Or do they need some additional JSON entries ?

With the above events file, I get "invalid event" for 'PM_INST_CMPL:u'

| Performance counter stats for 'true':
| 6,817 cpu/br_inst_exec.all_direct_jmp/
| 0.003503212 seconds time elapsed
| One nice feature is that a pointer to the specification update is now
| included in the description, which will hopefully clear up many problems:
| % perf list
| ...
| mem_load_uops_l3_hit_retired.xsnp_hit [Retired load uops which
| data sources were L3
| and cross-core snoop
| hits in on-pkg core
| cache. Supports address
| when precise. Spec
| update: HSM26, HSM30
| (Precise event)]
| ...
| -Andi
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