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Full Discussion: semaphore access speed
Top Forums Programming semaphore access speed Post 302238477 by otheus on Saturday 20th of September 2008 08:15:24 AM
Old 09-20-2008
Quote:
Originally Posted by jim mcnamara
PS call utimes(struct tms *) to actual times, plus granularity is CLK_TCK, usually way better than time().

gettimeofday can be used to get wall time even more accurately as well. utimes() returns clock_t wall time.
Jim, utimes() doesn't do what you think it does. Gettimeofday is more correct, but then the code is a bit more complicated. Microsecond differences would not produce the disparities in performance he is seeing.
 

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UTIME(3)						   BSD Library Functions Manual 						  UTIME(3)

NAME
utime -- set file times LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <utime.h> int utime(const char *path, const struct utimbuf *times); DESCRIPTION
This interface is obsoleted by utimes(2). The utime() function sets the access and modification times of the named file, based on the actime and modtime fields of the struct utimbuf pointed at by times. If the times are specified (the times argument is non-NULL), the caller must be the owner of the file or be the super-user. If the times are not specified (the times argument is NULL), the caller must be the owner of the file, have permission to write the file, or be the super-user. ERRORS
The utime() function may fail and set errno for any of the errors specified for the library function utimes(2). SEE ALSO
stat(2), utimes(2) STANDARDS
The utime() function conforms to IEEE Std 1003.1-1988 (``POSIX.1''). HISTORY
A utime() function appeared in Version 7 AT&T UNIX. BSD
June 4, 1993 BSD
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