• Song Liu's avatar
    perf/core: Fix ctx_event_type in ctx_resched() · bd903afe
    Song Liu authored
    In ctx_resched(), EVENT_FLEXIBLE should be sched_out when EVENT_PINNED is
    added. However, ctx_resched() calculates ctx_event_type before checking
    this condition. As a result, pinned events will NOT get higher priority
    than flexible events.
    
    The following shows this issue on an Intel CPU (where ref-cycles can
    only use one hardware counter).
    
      1. First start:
           perf stat -C 0 -e ref-cycles  -I 1000
      2. Then, in the second console, run:
           perf stat -C 0 -e ref-cycles:D -I 1000
    
    The second perf uses pinned events, which is expected to have higher
    priority. However, because it failed in ctx_resched(). It is never
    run.
    
    This patch fixes this by calculating ctx_event_type after re-evaluating
    event_type.
    Reported-by: default avatarEphraim Park <ephiepark@fb.com>
    Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: <jolsa@redhat.com>
    Cc: <kernel-team@fb.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vince Weaver <vincent.weaver@maine.edu>
    Fixes: 487f05e1 ("perf/core: Optimize event rescheduling on active contexts")
    Link: http://lkml.kernel.org/r/20180306055504.3283731-1-songliubraving@fb.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    bd903afe
core.c 267 KB