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Message-ID: <20140708184311.GA14707@us.ibm.com>
Date: Tue, 8 Jul 2014 11:43:11 -0700
From: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To: Andi Kleen <andi@...stfloor.org>
Cc: jolsa@...hat.com, linux-kernel@...r.kernel.org,
namhyung@...nel.org, acme@...radead.org
Subject: Re: perf: Add support for full Intel event lists v7
Andi Kleen [andi@...stfloor.org] 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| so the events in oprofile were often out of date.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://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc perf/json
|
| Example output:
|
| % perf download
| Downloading models file
| Downloading readme.txt
| 2014-03-05 10:39:33 URL:https://download.01.org/perfmon/readme.txt [10320/10320] -> "readme.txt" [1]
| 2014-03-05 10:39:34 URL:https://download.01.org/perfmon/mapfile.csv [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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