[MAPREDUCE-6391] util/Timer.cc completely misunderstands _POSIX_CPUTIME

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.0-alpha1
• Fix Version/s: 3.0.0-alpha1
• Component/s: build
• Assignee: Alan Burlison
• Reporter: Alan Burlison
• Created: 08/Jun/15 12:54
• Updated: 12/May/16 18:24
• Resolved: 27/Oct/15 19:08

Description

util/Timer.cc contains the following code:

clock_gettime(_POSIX_CPUTIME, &ts);

I'm not exactly sure what sort of time value this code is attempting to obtain (the process's on-CPU time perhaps?) but it is completely wrong, even on Linux. _POSIX_CPUTIME is a feature test macro and is not a valid parameter to clock_gettime. From the clock_gettime manpage:

The symbols _POSIX_MONOTONIC_CLOCK, _POSIX_CPUTIME, _POSIX_THREAD_CPUTIME indicate that CLOCK_MONOTONIC, CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID are available

On my Linux distro the value of _POSIX_CPUTIME is defined as 0. That corresponds to

#define __CLOCK_REALTIME0 0 /* obsolete; same as CLOCK_REALTIME */

And CLOCK_REALTIME is

#define CLOCK_REALTIME 3 /* wall clock */

Which I suspect is not what is required here.

Getting cross-platform CPU time is fiddly, the following blog post has a good summary: http://nadeausoftware.com/articles/2012/03/c_c_tip_how_measure_cpu_time_benchmarking (code examples are CC licensed so should be no taint issues)

Issue Links

• relates to: YARN-3719 Improve Solaris support in YARN