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PERL script slows down, strace shows FUTEX_WAIT

by ISAI student (Scribe)
on May 29, 2013 at 13:41 UTC ( #1035844=perlquestion: print w/ replies, xml ) Need Help??
ISAI student has asked for the wisdom of the Perl Monks concerning the following question:

Hello all.

I am running a PERL script, and it slowed down consderably. I have tried strace and found out that it outputs:

cs058:~$ strace -p 10067 Process 10067 attached - interrupt to quit futex(0x42e439d0, FUTEX_WAIT, 10089, NULL

Eventually it DOES complete. Looking at piped output shows slow progress. I have had some locking statements, now removed, but 0 effect. Any ideas?

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Re: PERL script slows down, strace shows FUTEX_WAIT
by BrowserUk (Pope) on May 29, 2013 at 14:00 UTC
    I have had some locking statements, now removed, but 0 effect.

    What type of locking statements? File locks? Shared data locks?

    If the latter, you'll be using a threaded perl; which also uses locks internally. The fact that strace shows the use of a futex does not indicate an error.

    Any ideas?

    Yes. Show us the code.

    Your post is like ringing your garage and telling them: I have a car; and when I listen to the engine it makes a clicking sound.

    Without you telling them the type of car; which engine it has; whether the clicking is fast or slow, low or high frequency, quiet or loud; whether the engine is running or not; you simply aren't even going to get a diagnosis of whether there is anything wrong, much less what.


    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
      I know, I know, but the workplace won't let me show it... I was shooting in the dark, and needed some sort of direction. I am locking shared variables. I am reading from a file line by line & doing work on it. I will see what I can do...
        but the workplace won't let me show it.

        Then recreate it. Remove any tell-tale comments. Change the variable and subroutine names to innocuous generic ones. If sample data is required to run it, create some that will work that has random string and numbers rather than actual data. Don't forget to remove anything that isn't required to demonstrate the problem.


        With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.

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