On Wed, Jan 29, 2025 at 05:16:58PM -0800, Ian Rogers wrote: > On Wed, Jan 29, 2025 at 1:55 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote: > > On Wed, Jan 15, 2025 at 01:20:32PM -0800, Ian Rogers wrote: > > > On Wed, Jan 15, 2025 at 9:59 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote: > > > > I think the behavior should be: > > > > > > > > cycles -> PERF_COUNT_HW_CPU_CYCLES > > > > cpu-cycles -> PERF_COUNT_HW_CPU_CYCLES > > > > cpu_cycles -> no legacy -> sysfs or json > > > > cpu/cycles/ -> sysfs or json > > > > cpu/cpu-cycles/ -> sysfs or json > > > > > > So I disagree as if you add a PMU to an event name the encoding > > > shouldn't change: > > > 1) This historically was perf's behavior. > > > > Well.. I'm not sure about the history. I believe the logic I said above > > is the historic and (I think) right behavior. > > You're wrong as you are describing the behavior post: > https://lore.kernel.org/r/20231123042922.834425-1-irogers@xxxxxxxxxx > commit a24d9d9dc096fc0d0bd85302c9a4fe4fe3b1107b from Nov 2022, but > somehow without legacy event fall backs which Intel added with a PMU > for hybrid. > > The behavior in this patch series is best for RISC-V, presumably ARM > (particularly for Apple M? CPUs), carries ARM and Intel's tags, > implements the behavior Arnaldo asked for, and solves the > inconsistency that I think is fundamentally wrong in the tool that PMU > names shouldn't matter on an event name (an inconsistency my past > fixes introduced). It is also part of solving other problems: > https://lore.kernel.org/linux-perf-users/20250127-counter_delegation-v3-0-64894d7e16d5@xxxxxxxxxxxx/ So you think the below behavior is preferred, right? cycles -> cpu/cycles/ (or whatever PMU name) -> sysfs or json And there's no way to use legacy event encodings anymore? > > You've not pointed at anything wrong in the scheme that these patches > introduce, and are supported by vendors, except that it is a behavior > change. I can, and have, pointed at many issues with your proposal > above and the current behavior. The behavior change came about to work > around PMU bugs over 2 years ago but only partially did so. It makes > sense to remedy this and for the clean, consistent behavior this > series achieves. It is unfortunate that it is a behavior change, but > the first step for that was made 2 years ago. I think it also makes > sense that something self described as legacy is a lower priority and > of the past (wrt event naming moving forward). I want to clarify the event parsing behavior and to find the right way to deal with various cases. I haven't followed the activities in this area closely so I missed some changes in the past. Maybe the problem is that the behavior is complex and not clarified. Hopefully we can write it down in a doc. Thanks, Namhyung
