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* gprof.texi (Sampling Error): Note that call counts and basic

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block counts are only reliable for multi-threaded applications if
        the counting function itself is thread safe.
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Nick Clifton 2010-06-08 10:38:48 +00:00
parent 9fbcbd8145
commit ede501f418
2 changed files with 14 additions and 4 deletions
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gprof/ChangeLog
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@ -1,3 +1,9 @@
2010-06-08 Nick Clifton <nickc@redhat.com>
* gprof.texi (Sampling Error): Note that call counts and basic
block counts are only reliable for multi-threaded applications if
the counting function itself is thread safe.
2010-06-08 Nick Clifton <nickc@redhat.com>
* gprof.texi: Replace abbreviated 20th century year numbers with

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gprof/gprof.texi
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@ -1615,10 +1615,14 @@ only a small amount of time, so that on the average the sampling process
ought to catch that function in the act only once, there is a pretty good
chance it will actually find that function zero times, or twice.
By contrast, the number-of-calls and basic-block figures
are derived by counting, not
sampling. They are completely accurate and will not vary from run to run
if your program is deterministic.
By contrast, the number-of-calls and basic-block figures are derived
by counting, not sampling. They are completely accurate and will not
vary from run to run if your program is deterministic and single
threaded. In multi-threaded applications, or single threaded
applications that link with multi-threaded libraries, the counts are
only deterministic if the counting function is thread-safe. (Note:
beware that the mcount counting function in glibc is @emph{not}
thread-safe). @xref{Implementation, ,Implementation of Profiling}.
The @dfn{sampling period} that is printed at the beginning of the flat
profile says how often samples are taken. The rule of thumb is that a