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authorIngo Molnar <mingo@elte.hu>2011-04-29 15:19:47 +0400
committerIngo Molnar <mingo@elte.hu>2011-04-29 16:23:58 +0400
commit8f62242246351b5a4bc0c1f00c0c7003edea128a (patch)
tree9021c99956e0f9dc64655aaa4309c0f0fdb055c9 /include/linux/perf_event.h
parentede70290046043b2638204cab55e26ea1d0c6cd9 (diff)
downloadlinux-8f62242246351b5a4bc0c1f00c0c7003edea128a.tar.xz
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.h3
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 */
};