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Full Discussion: Memory Barriers for (Ubuntu) Linux (i686)
Special Forums UNIX and Linux Applications High Performance Computing Memory Barriers for (Ubuntu) Linux (i686) Post 302430730 by Corona688 on Friday 18th of June 2010 01:34:12 PM
Old 06-18-2010
The old system(usually known as linuxthreads) has been abandoned for many moons now. It was designed to operate without modifying the kernel, which made it a very strange beast -- it created pretend-thread processes with 100% shared memory, did all communication with signal traps, and had some very....unique bugs that turned out to be fundamental design flaws(zombie threads! Wow!)

So, no. It was not a high-performance threading model. There's only a very few things(like ulibc in embedded systems) that still stick with it these days.

With kernel 2.5 and later, they built enough things into the kernel to let them do threading properly. I've shown you bits of its code -- some fundamental things are almost down to the instruction level. NPTL is much, much better, and I've found it quite good.

Quote:
I wanted to avoid the pthreads syncrhonisation structures like mutexes because I sought to avoid their overhead and keep it scalable.
Yes, and the overhead you were worried about was the same atomic operations you're hellbent on using now. I've looked in its code and shown you some of it; it's not bloated.
Quote:
There are ways to distribute work such that mutexes aren't necessary as long as an ordering of instructions can be guaranteed, hence following your advice, I'll try those atomic instructions from GCC.
I remain stolidly unconvinced that spinlocking is more efficient than blocking. If your writer really can keep up with your readers, a proper queue might not block at all even in pthreads.
Quote:
But anyway, I needed something with more control than was on offer with something featuring a standard posix api.
Are you sure of that? You only discovered thread-specific data last week.
Last edited by Corona688; 06-18-2010 at 02:42 PM..
 

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LEARN ABOUT DEBIAN

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
	      Don't open the bug in a browser at the end.

       -h, --help
	      Display a help message and exit.

       -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
	      against ftp.debian.org.

       --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
       variable takes precedence over the package-wide variable.

       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-
       fanor@ubuntu.com>.

       Both are released under the terms of the GNU General Public License, version 2.

ubuntu-dev-tools						 September 21 2010					 import-bug-from-debian(1)
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