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Re^7: Use more threads.

by password (Sexton)
on Apr 30, 2013 at 11:00 UTC ( #1031381=note: print w/ replies, xml ) Need Help??


in reply to Re^6: Use more threads.
in thread Use more threads.

I just used your code, it took 1.37 seconds. Then I added 9 lines of "use Modules" after "use strict" and now it takes 12.3 seconds:

use Socket; use IO::Socket; use DBI; use DBD::mysql; use Tk; use Tk::JPEG; use Tk::Table; use Tk::ProgressBarPlus; use LWP::UserAgent;

Adding "use LWP::UserAgent;" alone makes it run for over 5 seconds.

The complete code:

#! perl -slw use strict; use Socket; use IO::Socket; use DBI; use DBD::mysql; use Tk; use Tk::JPEG; use Tk::Table; use Tk::ProgressBarPlus; use LWP::UserAgent; use Time::HiRes qw[ time ]; use threads stack_size => 4096; my $start = time; async { #printf "%u starting\n", threads->tid; sleep 1e3 } ->detach for 1 .. 100; printf "Took %f seconds\n", time() - $start;


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Re^8: Use more threads.
by BrowserUk (Pope) on Apr 30, 2013 at 11:27 UTC

    Simple. Don't load everything into every thread.

    1. Tk isn't threadsafe so it has no business being loaded by more than 1 thread -- preferably the main thread -- so don't use it at the top of the code, require your TK::* modules after you've created your pool of threads.
    2. Likewise, it doesn't make much sense to have DBI/DBD modules in multiple threads. The DB server will serialise the accesses from the multiple threads anyway, with the result that queries and stores will be conflicting within the server and slowing each other down. So serialise it at your end. Start a dedicated DBI thread and queue your accesses to it.

    Those two steps alone cut the load time by half on my machine:

    C:\test>junk rem As your posted it. Took 4.529284 seconds C:\test>junk rem Tk required after threads started. Took 3.111319 seconds C:\test>junk rem DBI/DBD moved to separate thread. Took 2.166010 seconds

    And that is (probably) only the tip of the iceberg. With proper sight of your real code, there are probably lots more simple steps that could be done to improve things no end.


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