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https://github.com/openvswitch/ovs
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e81541398a
Commit 0eee08dbddea520536197657da7a0b (perf-counter: simplify the
performance macro) introduces the PERF macro, which is empty for non-linux
platforms.
Added to commit bc487aeff2 (ovsdb: Add per
transaction commit instruction counter), that uses such macro, it causes
segfaults, since it makes ovsdb_txn_commit return an uninitialized pointer as
error.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@redhat.com>
[blp@nicira.com added {} around the macro expansion]
Signed-off-by: Ben Pfaff <blp@nicira.com>
130 lines
4.0 KiB
C
130 lines
4.0 KiB
C
/*
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* Copyright (c) 2015 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef __PERF_COUNTER_H
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#define __PERF_COUNTER_H 1
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/* Motivation
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* ==========
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*
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* It is sometimes desirable to gain performance insights of a program
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* by using hardware counters. Recent Linux kernels started to support
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* a set of portable API for configuring and access those counter across
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* multiple platforms.
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*
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* APIs provided by perf-counter.h provides a set of APIs that are
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* semi-integrated into OVS user spaces. The infrastructure that initializes,
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* cleanup, display and clear them at run time is provided. However the
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* sample points are not. A programmer needs insert sample points when needed.
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*
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* Since there is no pre configured sample points, there is no run time
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* over head for the released product.
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*
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* Limitations
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* ===========
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* - Hard coded to sample CPU cycle count in user space only.
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* - Only one counter is sampled.
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* - Useful macros are only provided for function profiling.
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* - show and clear command applies to all counters, there is no way
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* to select a sub-set of counter.
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*
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* Those are not fundamental limits, but only limited by current
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* implementation.
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*
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* Usage:
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* =======
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*
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* Adding performance counter is easy. Simply use the following macro to
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* wrap around the expression you are interested in measuring.
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*
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* PERF(name, expr).
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*
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* The 'expr' is a set of C expressions you are interested in measuring.
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* 'name' is the counter name.
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*
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* For example, if we are interested in performance of perf_func():
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*
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* int perf_func() {
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* <implemenation>
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* }
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*
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* void func() {
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* int rt;
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*
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* ...
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* PERF("perf_func", rt = perf_func());
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*
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* return rt;
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* }
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*
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*
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* This will maintain the number of times 'perf_func()' is called, total
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* number of instructions '<implementation>' plus function call overhead
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* executed.
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*
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*/
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#if defined(__linux__) && defined(HAVE_LINUX_PERF_EVENT_H)
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struct perf_counter {
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const char *name;
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bool once;
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uint64_t n_events;
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uint64_t total_count;
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};
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#define PERF_COUNTER_ONCE_INITIALIZER(name) \
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{ \
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name, \
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false, \
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0, \
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0, \
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}
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void perf_counters_init(void);
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void perf_counters_destroy(void);
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void perf_counters_clear(void);
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uint64_t perf_counter_read(uint64_t *counter);
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void perf_counter_accumulate(struct perf_counter *counter,
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uint64_t start_count);
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char *perf_counters_to_string(void);
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/* User access macros. */
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#define PERF(name, expr) \
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{ \
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static struct perf_counter c = PERF_COUNTER_ONCE_INITIALIZER(name);\
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uint64_t start_count = perf_counter_read(&start_count); \
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\
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expr; \
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\
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perf_counter_accumulate(&c, start_count); \
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}
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#else
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#define PERF(name, expr) { expr; }
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static inline void perf_counters_init(void) {}
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static inline void perf_counters_destroy(void) {}
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static inline void perf_counters_clear(void) {}
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static inline char *
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perf_counters_to_string(void)
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{
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return xstrdup("Not Supported on this platform. Only available on Linux (version >= 2.6.32)");
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}
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#endif
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#endif
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