diff options
| author | Ingo Molnar <mingo@elte.hu> | 2011-04-29 13:19:47 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-04-29 14:23:58 +0200 |
| commit | 8f62242246351b5a4bc0c1f00c0c7003edea128a (patch) | |
| tree | 9021c99956e0f9dc64655aaa4309c0f0fdb055c9 /include/linux/perf_event.h | |
| parent | ede70290046043b2638204cab55e26ea1d0c6cd9 (diff) | |
perf events: Add generic front-end and back-end stalled cycle event definitions
Add two generic hardware events: front-end and back-end stalled cycles.
These events measure conditions when the CPU is executing code but its
capabilities are not fully utilized. Understanding such situations and
analyzing them is an important sub-task of code optimization workflows.
Both events limit performance: most front end stalls tend to be caused
by branch misprediction or instruction fetch cachemisses, backend
stalls can be caused by various resource shortages or inefficient
instruction scheduling.
Front-end stalls are the more important ones: code cannot run fast
if the instruction stream is not being kept up.
An over-utilized back-end can cause front-end stalls and thus
has to be kept an eye on as well.
The exact composition is very program logic and instruction mix
dependent.
We use the terms 'stall', 'front-end' and 'back-end' loosely and
try to use the best available events from specific CPUs that
approximate these concepts.
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/n/tip-7y40wib8n000io7hjpn1dsrm@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/linux/perf_event.h')
| -rw-r--r-- | include/linux/perf_event.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index ac636dd20a0c..4e2d7ae71499 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -52,7 +52,8 @@ enum perf_hw_id { PERF_COUNT_HW_BRANCH_INSTRUCTIONS = 4, PERF_COUNT_HW_BRANCH_MISSES = 5, PERF_COUNT_HW_BUS_CYCLES = 6, - PERF_COUNT_HW_STALLED_CYCLES = 7, + PERF_COUNT_HW_STALLED_CYCLES_FRONTEND = 7, + PERF_COUNT_HW_STALLED_CYCLES_BACKEND = 8, PERF_COUNT_HW_MAX, /* non-ABI */ }; |