[v2: Review feedback addressed and some minor improvements] 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 Unfortunately oprofile usually did not keep up with these updates, so the events in oprofile were often out of date.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 ~/.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. 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 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
