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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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RUNLIM(1)						      General Commands Manual							 RUNLIM(1)

NAME
runlim - a program to run benchmarks SYNOPSIS
runlim [ options ...] command [ arguments ...] DESCRIPTION
run is a tool that can be used to run and control benchmarks. It executes a given command with (optional) arguments, samples resource usage during the run, and kills the process (and its child processes) if a certain time and/or space limit is exhausted. Every 100 milliseconds, runlim takes a sample of the program's resource utilization, and logs status information to stderr every second. Optionally, the status can be logged to a file. Multi-threaded programs can be limited by setting a wall clock timeout. runlim follows the time accumulation scheme of GNU time for multi- threaded programs and programs that spawn multiple child-processes: time spent in each thread/child is summed up, unless you are only interested in walk clock time. OPTIONS
runlim accepts the following options: -h, --help Show summary of options. --version Show version of program. -o FILE, --output-file=FILE Overwrite or create FILE for output logging. -s NUM, --space-limit=NUM Set space limit to NUM megabytes. -t NUM, --time-limit=NUM Set time limit to NUM seconds. -r NUM, --real-time-limit=NUM Set real time limit to NUM seconds. -k, --kill Propagate signals. SEE ALSO
time(1), timelimit(1), timeout(1), time(7). AUTHOR
runlim was written by Armin Biere and Toni Jussila. This manual page was written by Thomas Krennwallner <tkren@kr.tuwien.ac.at>, for the Debian project (and may be used by others). February 11, 2011 RUNLIM(1)
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