summaryrefslogtreecommitdiff
path: root/trace.h
diff options
context:
space:
mode:
authorKarsten Blees <karsten.blees@gmail.com>2014-07-12 02:05:42 +0200
committerJunio C Hamano <gitster@pobox.com>2014-07-13 21:25:20 -0700
commit148d6771bf5e00aa1d7fa2221507a3dfe4c1e37f (patch)
treecd30a7457601f286b0238d8b69d2528abfcaaa76 /trace.h
parente05bed960d3bf3bcfd0f27ab882df3da93e118ed (diff)
downloadgit-148d6771bf5e00aa1d7fa2221507a3dfe4c1e37f.tar.gz
trace: add high resolution timer function to debug performance issues
Add a getnanotime() function that returns nanoseconds since 01/01/1970 as unsigned 64-bit integer (i.e. overflows in july 2554). This is easier to work with than e.g. struct timeval or struct timespec. Basing the timer on the epoch allows using the results with other time-related APIs. To simplify adaption to different platforms, split the implementation into a common getnanotime() and a platform-specific highres_nanos() function. The common getnanotime() function handles errors, falling back to gettimeofday() if highres_nanos() isn't implemented or doesn't work. getnanotime() is also responsible for normalizing to the epoch. The offset to the system clock is calculated only once on initialization, i.e. manually setting the system clock has no impact on the timer (except if the fallback gettimeofday() is in use). Git processes are typically short lived, so we don't need to handle clock drift. The highres_nanos() function returns monotonically increasing nanoseconds relative to some arbitrary point in time (e.g. system boot), or 0 on failure. Providing platform-specific implementations should be relatively easy, e.g. adapting to clock_gettime() as defined by the POSIX realtime extensions is seven lines of code. This version includes highres_nanos() implementations for: * Linux: using clock_gettime(CLOCK_MONOTONIC) * Windows: using QueryPerformanceCounter() Todo: * enable clock_gettime() on more platforms * add Mac OSX version, e.g. using mach_absolute_time + mach_timebase_info Signed-off-by: Karsten Blees <blees@dcon.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'trace.h')
-rw-r--r--trace.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/trace.h b/trace.h
index 7a5ba2e61c..4b893a55cf 100644
--- a/trace.h
+++ b/trace.h
@@ -16,6 +16,7 @@ struct trace_key {
extern void trace_repo_setup(const char *prefix);
extern int trace_want(struct trace_key *key);
extern void trace_disable(struct trace_key *key);
+extern uint64_t getnanotime(void);
#ifndef HAVE_VARIADIC_MACROS