Getrusage(2) weirdness.

[Frank Mayhar]

I recently had occasion to need the ru_maxrss field returned from
getrusage(2) in Linux 2.6, which as it happens was not implemented.  So
I implemented it.  In the process I wrote a test program to validate my
implementation.  I also tried running the test under various other
operating systems, including FreeBSD 6-stable.  Most systems don't
implement the field (including Solaris and MacOSX), FreeBSD is one of
the few that does.

Only, it does so weirdly.

You can find the test program at
    http://www.exit.com/Archives/Linux/getrusage-test.c
The output should be pretty self-explanatory.  If you run it under
FreeBSD 6.2 (at least), you will find that it give inconsistent results.
Something like the following:

jill ~>./getrusage-test
before 0 after: 0
1:  rusage_self:  FAIL
flag 6 granddad 0, kid1 0, kid2 0, kid3 0 kid4 0 kid5 2372 sz 1365
2:  rusage_grandchildren:  PASS
flag 3 dad 0, kid1 2372, kid2 2372, kid3 2372 kid4 2372 sz 2048
3:  rusage_children:  FAIL
flag 3 dad 0, kid1 2372, kid2 2372, kid3 2372 kid4 2372 sz 4096
4:  rusage_ignorechildren:  PASS
jill ~>./getrusage-test
before 0 after: 968
1:  rusage_self:  FAIL
flag 6 granddad 968, kid1 0, kid2 0, kid3 0 kid4 0 kid5 0 sz 1365
2:  rusage_grandchildren:  FAIL
flag 3 dad 968, kid1 0, kid2 0, kid3 0 kid4 3572 sz 2048
3:  rusage_children:  PASS
flag 3 dad 1820, kid1 3572, kid2 3572, kid3 3572 kid4 3572 sz 4096
4:  rusage_ignorechildren:  PASS
jill ~>./getrusage-test
before 0 after: 0
1:  rusage_self:  FAIL
flag 6 granddad 0, kid1 0, kid2 0, kid3 0 kid4 0 kid5 2336 sz 1365
2:  rusage_grandchildren:  PASS
flag 3 dad 1760, kid1 2336, kid2 2336, kid3 2336 kid4 2336 sz 2048
3:  rusage_children:  FAIL
flag 3 dad 1760, kid1 2336, kid2 2336, kid3 2336 kid4 2336 sz 4096
4:  rusage_ignorechildren:  PASS
jill ~>./getrusage-test
before 0 after: 1144
1:  rusage_self:  PASS
flag 6 granddad 1144, kid1 0, kid2 0, kid3 0 kid4 0 kid5 0 sz 1365
2:  rusage_grandchildren:  FAIL
flag 3 dad 1144, kid1 0, kid2 0, kid3 0 kid4 0 sz 2048
3:  rusage_children:  FAIL
flag 3 dad 1144, kid1 0, kid2 0, kid3 0 kid4 0 sz 4096
4:  rusage_ignorechildren:  PASS
jill ~>./getrusage-test
before 0 after: 0
1:  rusage_self:  FAIL
flag 6 granddad 0, kid1 0, kid2 0, kid3 0 kid4 0 kid5 1936 sz 1365
2:  rusage_grandchildren:  PASS
flag 3 dad 1760, kid1 1936, kid2 1936, kid3 1936 kid4 1936 sz 2048
3:  rusage_children:  FAIL
flag 3 dad 1760, kid1 1936, kid2 1936, kid3 1936 kid4 1936 sz 4096
4:  rusage_ignorechildren:  PASS
jill ~>./getrusage-test
before 0 after: 0
1:  rusage_self:  FAIL
flag 6 granddad 0, kid1 0, kid2 0, kid3 0 kid4 0 kid5 0 sz 1365
2:  rusage_grandchildren:  FAIL
flag 3 dad 0, kid1 0, kid2 0, kid3 0 kid4 3052 sz 2048
3:  rusage_children:  PASS
flag 3 dad 0, kid1 3052, kid2 3052, kid3 3052 kid4 3052 sz 4096
4:  rusage_ignorechildren:  PASS
jill ~>./getrusage-test
before 0 after: 0
1:  rusage_self:  FAIL
flag 6 granddad 0, kid1 0, kid2 0, kid3 0 kid4 0 kid5 0 sz 1365
2:  rusage_grandchildren:  FAIL
flag 3 dad 0, kid1 0, kid2 0, kid3 0 kid4 3208 sz 2048
3:  rusage_children:  PASS
flag 3 dad 0, kid1 3208, kid2 3208, kid3 3208 kid4 3208 sz 4096
4:  rusage_ignorechildren:  PASS
jill ~>./getrusage-test
before 492 after: 492
1:  rusage_self:  FAIL
flag 6 granddad 492, kid1 0, kid2 0, kid3 0 kid4 0 kid5 0 sz 1365
2:  rusage_grandchildren:  FAIL
flag 3 dad 492, kid1 0, kid2 0, kid3 0 kid4 0 sz 2048
3:  rusage_children:  FAIL
flag 3 dad 492, kid1 0, kid2 0, kid3 0 kid4 0 sz 4096
4:  rusage_ignorechildren:  PASS
jill ~>./getrusage-test
before 444 after: 444
1:  rusage_self:  FAIL
flag 6 granddad 444, kid1 0, kid2 0, kid3 0 kid4 0 kid5 0 sz 1365
2:  rusage_grandchildren:  FAIL
flag 3 dad 444, kid1 0, kid2 0, kid3 0 kid4 0 sz 2048
3:  rusage_children:  FAIL
flag 3 dad 444, kid1 0, kid2 0, kid3 0 kid4 0 sz 4096
4:  rusage_ignorechildren:  PASS

-- 
Frank Mayhar frank at exit.com     http://www.exit.com/
Exit Consulting                 http://www.gpsclock.com/
                                http://www.exit.com/blog/frank/
                                http://www.zazzle.com/fmayhar*