On Wed, Sep 08, 2021 at 05:17:53PM +1000, Michael Ellerman wrote: > Kajol Jain <kj...@linux.ibm.com> writes:
> > diff --git a/include/uapi/linux/perf_event.h > > b/include/uapi/linux/perf_event.h > > index f92880a15645..030b3e990ac3 100644 > > --- a/include/uapi/linux/perf_event.h > > +++ b/include/uapi/linux/perf_event.h > > @@ -1265,7 +1265,9 @@ union perf_mem_data_src { > > #define PERF_MEM_LVLNUM_L2 0x02 /* L2 */ > > #define PERF_MEM_LVLNUM_L3 0x03 /* L3 */ > > #define PERF_MEM_LVLNUM_L4 0x04 /* L4 */ > > -/* 5-0xa available */ > > +#define PERF_MEM_LVLNUM_OC_L2 0x05 /* On Chip L2 */ > > +#define PERF_MEM_LVLNUM_OC_L3 0x06 /* On Chip L3 */ > > The obvious use for 5 is for "L5" and so on. > > I'm not sure adding new levels is the best idea, because these don't fit > neatly into the hierarchy, they are off to the side. > > > I wonder if we should use the remote field. > > ie. for another core's L2 we set: > > mem_lvl = PERF_MEM_LVL_L2 > mem_remote = 1 This mixes APIs (see below), IIUC the correct usage would be something like: lvl_num=L2 remote=1 > Which would mean "remote L2", but not remote enough to be > lvl = PERF_MEM_LVL_REM_CCE1. > > It would be printed by the existing tools/perf code as "Remote L2", vs > "Remote cache (1 hop)", which seems OK. > > > ie. we'd be able to express: > > Current core's L2: LVL_L2 > Other core's L2: LVL_L2 | REMOTE > Other chip's L2: LVL_REM_CCE1 | REMOTE > > And similarly for L3. > > I think that makes sense? Unless people think remote should be reserved > to mean on another chip, though we already have REM_CCE1 for that. IIRC the PERF_MEM_LVL_* namespace is somewhat depricated in favour of the newer composite PERF_MEM_{LVLNUM_,REMOTE_,SNOOPX_} fields. Of course, ABIs being what they are, we get to support both :/ But I'm not sure mixing them is a great idea. Also, clearly this could use a comment... The 'new' composite doesnt have a hops field because the hardware that nessecitated that change doesn't report it, but we could easily add a field there. Suppose we add, mem_hops:3 (would 6 hops be too small?) and the corresponding PERF_MEM_HOPS_{NA, 0..6} Then I suppose you can encode things like: L2 - local L2 L2 | REMOTE - remote L2 at an unspecified distance (NA) L2 | REMOTE | HOPS_0 - remote L2 on the same node L2 | REMOTE | HOPS_1 - remote L2 on a node 1 removed Would that work?