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Full Discussion: semaphore access speed
Top Forums Programming semaphore access speed Post 302239428 by migurus on Tuesday 23rd of September 2008 03:46:38 PM
Old 09-23-2008
to Otheus:
gprof -l complains about missing call-graph data, which I don't quite understand, but that is beyond the point in this thread.

to Jim:

On SCO
$ truss ./tstloop
semsys(1, 2819742, 2, 0, 0, 0) = 18827
semsys(0, 18827, 2, 6, 2147483024, 0) = 0
.
.
.
repeats on and on for 5,000,000 times, as coded.
I don't see any brk here.

On Linux
$ strace -Tc ./tstloop
time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
50.85 62.145774 29 2134526 semctl
49.15 60.059067 28 2134527 semget
0.00 0.000088 18 5 old_mmap
0.00 0.000054 18 3 mprotect
0.00 0.000039 20 2 open
0.00 0.000028 14 2 fstat64
0.00 0.000025 13 2 close
0.00 0.000020 20 1 munmap
0.00 0.000018 18 1 read
0.00 0.000018 18 1 uname
0.00 0.000018 18 1 stat64
0.00 0.000014 14 1 1 access
0.00 0.000014 14 1 set_thread_area
0.00 0.000012 12 1 time
0.00 0.000008 8 1 brk
------ ----------- ----------- --------- --------- ----------------
100.00 122.205197 4269075 1 total

when I try
$ strace ./tstloop
semget(1660977153, 2, IPC_CREAT|0777) = 32769 <0.000028>
semctl(32769, 2, IPC_64|GETALL, 0xfeead064) = 0 <0.000029>
.
.
.

Does this output clarifies anything?
 

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IPC(2)							     Linux Programmer's Manual							    IPC(2)

NAME
ipc - System V IPC system calls SYNOPSIS
int ipc(unsigned int call, int first, int second, int third, void *ptr, long fifth); DESCRIPTION
ipc() is a common kernel entry point for the System V IPC calls for messages, semaphores, and shared memory. call determines which IPC function to invoke; the other arguments are passed through to the appropriate call. User programs should call the appropriate functions by their usual names. Only standard library implementors and kernel hackers need to know about ipc(). CONFORMING TO
ipc() is Linux-specific, and should not be used in programs intended to be portable. NOTES
On a few architectures, for example ia64, there is no ipc() system call; instead msgctl(2), semctl(2), shmctl(2), and so on really are implemented as separate system calls. SEE ALSO
msgctl(2), msgget(2), msgrcv(2), msgsnd(2), semctl(2), semget(2), semop(2), semtimedop(2), shmat(2), shmctl(2), shmdt(2), shmget(2) COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2007-06-28 IPC(2)
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