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MDEV-8692 prefschema test failures on ARM (on Debian build system)

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A few tests assumes that the CYCLE timer is always available,
which is not true on some platforms (e.g. ARM).
Fixing the tests not to reply on the CYCLE availability.
This commit is contained in:
Alexander Barkov
2015-10-30 10:10:43 +04:00
parent 56f04e0dfd
commit 59dd58b17e
6 changed files with 41 additions and 6 deletions
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25
mysys/my_rdtsc.c
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@@ -129,6 +129,31 @@ ulonglong my_timer_cycles_il_x86_64();
clock_gettime(CLOCK_SGI_CYCLE) for Irix platforms,
or on read_real_time for aix platforms. There is
nothing for Alpha platforms, they would be tricky.
On the platforms that do not have a CYCLE timer,
"wait" events are initialized to use NANOSECOND instead of CYCLE
during performance_schema initialization (at the server startup).
Linux performance monitor (see "man perf_event_open") can
provide cycle counter on the platforms that do not have
other kinds of cycle counters. But we don't use it so far.
ARM notes
---------
During tests on ARMv7 Debian, perf_even_open() based cycle counter provided
too low frequency with too high overhead:
MariaDB [performance_schema]> SELECT * FROM performance_timers;
+-------------+-----------------+------------------+----------------+
| TIMER_NAME | TIMER_FREQUENCY | TIMER_RESOLUTION | TIMER_OVERHEAD |
+-------------+-----------------+------------------+----------------+
| CYCLE | 689368159 | 1 | 970 |
| NANOSECOND | 1000000000 | 1 | 308 |
| MICROSECOND | 1000000 | 1 | 417 |
| MILLISECOND | 1000 | 1000 | 407 |
| TICK | 127 | 1 | 612 |
+-------------+-----------------+------------------+----------------+
Therefore, it was decided not to use perf_even_open() on ARM
(i.e. go without CYCLE and have "wait" events use NANOSECOND by default).
*/
ulonglong my_timer_cycles(void)