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Special Forums UNIX and Linux Applications High Performance Computing Memory Barriers for (Ubuntu) Linux (i686) Post 302430462 by Corona688 on Thursday 17th of June 2010 05:25:35 PM
Old 06-17-2010
P.S. On a two-core single-CPU system, the overhead of XCHG vs LOCK XCHG with five seperate processes:

Code:
$ ./a.out & ./a.out & ./a.out & ./a.out & ./a.out &
12225 !Lock     time = 0 M 8 S 657 ms 205 us = 0.116 Mops/s
12229 !Lock     time = 0 M 8 S 801 ms 676 us = 0.114 Mops/s
12227 !Lock     time = 0 M 8 S 896 ms 459 us = 0.112 Mops/s
12228 !Lock     time = 0 M 8 S 958 ms 739 us = 0.112 Mops/s
12226 !Lock     time = 0 M 9 S 157 ms 723 us = 0.109 Mops/s
12228 Lock      time = 0 M 8 S 610 ms 749 us = 0.116 Mops/s
12227 Lock      time = 0 M 8 S 719 ms 860 us = 0.115 Mops/s
12225 Lock      time = 0 M 9 S 49 ms 622 us = 0.111 Mops/s
12226 Lock      time = 0 M 8 S 608 ms 304 us = 0.116 Mops/s
12229 Lock      time = 0 M 9 S 48 ms 352 us = 0.111 Mops/s

The code is a million loops of this:
Code:
                        "LOOP1:                 \n"
                        "       xchg    %ebx, a \n"
                        "       xchg    %ebx, a \n"
                        "       xchg    %ebx, a \n"
                        "       xchg    %ebx, a \n"
                        "       xchg    %ebx, a \n"
                        "       loop    LOOP1   \n"

except once with LOCK XCHG, one with just XCHG. No significant difference.

---------- Post updated at 03:25 PM ---------- Previous update was at 03:14 PM ----------

Quote:
Originally Posted by gorga
I originally used it with existing thread-pools, but found I needed more control over the allocation of "tasks" to "cores"
How so?
Quote:
hence I'm making my own.
I don't see how using a different structure excludes pthreads. You wanted to avoid pthreads since it used atomic ops, and are prepared to use atomic ops instead? It's best to write portably if possible anyway.

Last edited by Corona688; 06-17-2010 at 06:42 PM..
 

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libmlib_mt(3LIB)														  libmlib_mt(3LIB)

NAME
libmlib_mt - multi-threaded mediaLib SYNOPSIS
cc [ flag... ] file... -lmlib_mt -lmlib [ library... ] #include <mlib.h> Interfaces in this library provide functions for multimedia processing. Multi-threaded (MT) mediaLib is a software layer developed on top of mediaLib using OpenMP. When it is used with a large data set on a multi-processor system, MT mediaLib will partition data into subsets and process the subsets in parallel, thus greatly improving performance of applications that use mediaLib. INTERFACES
The shared object libmlib_mt.so.2 provides the same public interfaces as those defined in libmlib(3lib). See intro(3) for additional infor- mation on shared object interfaces. There are two ways to use MT mediaLib. 1. Pre-load a multi-threaded mediaLib library during runtime by setting the LD_PRELOAD environment variable as follows before starting your application, in Bourne/Korn shell: LD_PRELOAD=libmlib_mt.so export LD_PRELOAD or in C shell: setenv LD_PRELOAD libmlib_mt.so In this way, you can take advantage of MT mediaLib without rebuilding your application. 2. Link your application with a multi-threaded mediaLib library directly as shown under . In this way, an MT mediaLib library is always used whenever your application is started. The parallelization of MT mediaLib is controlled, in part, by the PARALLEL environment variable. You can change its setting to adjust the degree of parallelization before starting your application, in Bourne/Korn shell: PARALLEL=n export PARALLEL or in C shell: setenv PARALLEL n where n is a positive integer for number of threads. Note that other factors also affect the degree of parallelization in MT mediaLib. /usr/lib/libmlib_mt.so.2 shared object /usr/lib/64/libmlib_mt.so.2 64-bit shared object See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWmlibt | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ Intro(3), libmlib(3lib), attributes(5) 30 Sep 2005 libmlib_mt(3LIB)
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