Hi, On 10.10.2018 13:45, Peter Zijlstra wrote: > Hi all, > > There have been various issues and limitations with the way perf uses > (task) contexts to track events. Most notable is the single hardware PMU > task context, which has resulted in a number of yucky things (both > proposed and merged). > > Notably: > > - HW breakpoint PMU > - ARM big.little PMU > - Intel Branch Monitoring PMU > > Since we now track the events in RB trees, we can 'simply' add a pmu > order to them and have them grouped that way, reducing to a single > context. Of course, reality never quite works out that simple, and below > ends up adding an intermediate data structure to bridge the context -> > pmu mapping. > > Something a little like: > > ,------------------------[1:n]---------------------. > V V > perf_event_context <-[1:n]-> perf_event_pmu_context <--- perf_event > ^ ^ | | > `--------[1:n]---------' `-[n:1]-> pmu <-[1:n]-' > > This patch builds (provided you disable CGROUP_PERF), boots and survives > perf-top without the machine catching fire. > > There's still a fair bit of loose ends (look for XXX), but I think this > is the direction we should be going. > > Comments? > > Not-Quite-Signed-off-by: Peter Zijlstra (Intel) <[email protected]> > --- > arch/powerpc/perf/core-book3s.c | 4 > arch/x86/events/core.c | 4 > arch/x86/events/intel/core.c | 6 > arch/x86/events/intel/ds.c | 6 > arch/x86/events/intel/lbr.c | 16 > arch/x86/events/perf_event.h | 6 > include/linux/perf_event.h | 80 +- > include/linux/sched.h | 2 > kernel/events/core.c | 1412 > ++++++++++++++++++++-------------------- > 9 files changed, 815 insertions(+), 721 deletions(-)
Rewrite is impressive however it doesn't result in code base reduction as it is. Nonetheless there is a clear demand for per pmu events groups tracking and rotation in single cpu context (HW breakpoints, ARM big.little, Intel LBRs) and there is a supply thru groups ordering on RB-tree. This might be driven into the kernel by some new Perf features that would base on that RB-tree groups ordering or by refactoring of existing code but in the way it would result in overall code base reduction thus lowering support cost. Thanks, Alexey
