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Full Discussion: semaphore access speed
Top Forums Programming semaphore access speed Post 302245538 by otheus on Friday 10th of October 2008 10:07:07 AM
Old 10-10-2008
SemOp Benchmarks on various Linux servers
I have run benchmarks on the following hardware:
  • Xeon 3600, 1024k Cache, no SEP, no model #
  • Xeon 2800, 512k Cache, no SEP, no model #
  • Xeon 2333, 4095k Cache, no SEP, E5E45
  • Opteron 1000, 1024k Cache, no SEP, 270
  • Opteron 2000, 1024k Cache, SEP, 270
  • Opteron 2600, 1024k Cache, no SEP, 285
  • Opteron 2600, 1024k Cache, SEP, 285
These systems were under various amounts of load, so averages were taken, and they cannot be deemed 100% reliable. The benchmarks used a gettimeofday() call which looped for at least 3 seconds. The attached PDFs shows the results in terms of "Tics per SemOp". and "SemOps per Second".

Observations:
The Opteron 270 running at 1GHz and using int 80 for system calls was the fastest per clock tic. The fastest processors (the Xeons) were the slowest. This suggests the problem is the memory access.

The raw numbers show that the sysent call on the Opteron makes the semop about 14% faster. Static compilation generally improved speeds, though because of system load, I would not put much significance on these numbers. The only dynamic linking, really, is the library call to invoke a system call.

Analysis:
I'm going to leave it to others to explain this data.
Semops Benchmark.pdf (123.7 KB) 
Semops Benchmark2.pdf (124.8 KB) 
 

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LEARN ABOUT OPENSOLARIS

semaphore.h

semaphore.h(3HEAD)						      Headers							semaphore.h(3HEAD)

NAME

       semaphore.h, semaphore - semaphores

SYNOPSIS

       #include <semaphore.h>

DESCRIPTION

       The  <semaphore.h>  header  defines  the sem_t type, used in performing semaphore operations. The semaphore can be implemented using a file
       descriptor, in which case applications are able to open up at least a total of {OPEN_MAX} files and semaphores. The  symbol  SEM_FAILED	is
       defined (see sem_open(3C)).

       Inclusion  of  the <semaphore.h> header can make visible symbols defined in the headers <fcntl.h> and <sys/types.h>. See fcntl.h(3HEAD) and
       types.h(3HEAD).

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |Standard		     |See standards(5). 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       fcntl.h(3HEAD),	types.h(3HEAD),  sem_destroy(3C),   sem_getvalue(3C),	sem_init(3C),	sem_open(3C),	sem_post(3C),	sem_timedwait(3C),
       sem_unlink(3C), sem_wait(3C), attributes(5), standards(5)

SunOS 5.11							    5 Feb 2008							semaphore.h(3HEAD)
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