Memory Barriers for (Ubuntu) Linux (i686) Post: 302430462

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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

06-17-2010

Registered User

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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import-bug-from-debian

import-bug-from-debian(1)				      General Commands Manual					 import-bug-from-debian(1)

NAME

       import-bug-from-debian - Import bugs from Debian's BTS, and file them against Ubuntu in LP.

SYNOPSIS

       import-bug-from-debian [options] bug...
       import-bug-from-debian -h

DESCRIPTION

       import-bug-from-debian  clones  bugs  from Debian's BTS into Launchpad. Each bug listed on the command line has its initial report re-filed
       against the same source package in Ubuntu.  The Ubuntu bug is linked back to its Debian counterpart.

       Each bug may be provided either as a bug number or URL.

OPTIONS

       -b, --browserless
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       -h, --help
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       -l INSTANCE, --lpinstance=INSTANCE
	      Use the specified instance of Launchpad (e.g. "staging"), instead of the default of "production".

       -p PACKAGE, --package=PACKAGE
	      Launchpad package to file bug against, if not the same source package name as Debian.   Useful  for  importing  removal  bugs  filed
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       --no-conf
	      Do not read any configuration files, or configuration from environment variables.

ENVIRONMENT

       All  of	the  CONFIGURATION  VARIABLES  below are also supported as environment variables.  Variables in the environment take precedence to
       those in configuration files.

CONFIGURATION VARIABLES

       The following variables can be set in the environment or in ubuntu-dev-tools(5) configuration files.  In  each  case,  the  script-specific
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       IMPORT_BUG_FROM_DEBIAN_LPINSTANCE, UBUNTUTOOLS_LPINSTANCE
	      The default value for --lpinstance.

SEE ALSO

       ubuntu-dev-tools(5)

AUTHORS

       import-bug-from-debian  was  written  by  James	Westby <james.westby@ubuntu.com>, and this manual page was written by Stefano Rivera <ste-
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ubuntu-dev-tools						 September 21 2010					 import-bug-from-debian(1)