Re^5: Threaded Code Not Faster Than Non-Threaded -- Why?

It seems like it will take a bit of experimentation to figure out how long to sleep and how deep to keep the queue.

These are not as critical as you might first think.

sleep: A thread that calls $Q->pending once every millisecond will consume so few cycles that it barely registers on taskmanager/top.
Try this:
```
perl -MThread::Queue -E"$Q=new Thread::Queue; $Q->pending while Win32:
+:Sleep( 1 )"
[download]
```
On my system, that shows up in Process Manager as 0.0%.
So, running it at a frequency of once every timeslice -- ~10 milliseconds -- will consume negligible cpu whilst ensuring that the queue is (re)populated in a timely manner.
Queue Length: A queue, shared between 16 threads, populated with a million longish paths, will consume less than 200MB.
Try:
```
perl -Mthreads -MThread::Queue -E"async{ sleep }->detach for 1 .. 16; 
+$Q=new Thread::Queue; $Q->enqueue( qq[/a/longish/path/and/filename$_]
+ ) for 1 .. 1e6; sleep;"
[download]
```
Which given a typical modern system with 4-16 GB is nothing to concern ourselves with; and is at least 3 order of magnitude greater than I'd recommend as a starting point (100 for 16 threads).

For IO-bound process like this, tuning either or both variables over quiet a large range of values will have little or no effect on overall throughput.

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Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

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In the absence of evidence, opinion is indistinguishable from prejudice.

Comment on Re^5: Threaded Code Not Faster Than Non-Threaded -- Why? Select or Download Code

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Re^6: Threaded Code Not Faster Than Non-Threaded -- Why? by Tommy (Chaplain) on Jan 06, 2014 at 03:15 UTC
The results are in. I forked and refactored the code to follow the pattern you laid out (BrowserUk). The threaded part of the code is over 2X faster now! Thanks again! Tommy A mistake can be valuable or costly, depending on how faithfully you pursue correction	[reply]
Re^7: Threaded Code Not Faster Than Non-Threaded -- Why? by BrowserUk (Patriarch) on Jan 06, 2014 at 03:25 UTC
Could you post (a link to) your latest code? 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.	[reply]
Re^8: Threaded Code Not Faster Than Non-Threaded -- Why? by Tommy (Chaplain) on Jan 06, 2014 at 04:55 UTC
It isn't nearly finished and is undergoing a transformation since I typed my response, but at the time of this writing you can find the threading code here One of the first things you'll notice is that I didn't implement a "guard" or "doorman". I'm just stuffing everything in the queue for now. Even on directory trees larger than 200GB it barely takes more than 200MB RAM. Tommy A mistake can be valuable or costly, depending on how faithfully you pursue correction	[reply]
Re^9: Threaded Code Not Faster Than Non-Threaded -- Why? by BrowserUk (Patriarch) on Jan 06, 2014 at 07:06 UTC
Re^10: Threaded Code Not Faster Than Non-Threaded -- Why? by Tommy (Chaplain) on Jan 06, 2014 at 18:27 UTC
Some notes below your chosen depth have not been shown here
Re^8: Threaded Code Not Faster Than Non-Threaded -- Why? by Tommy (Chaplain) on Jan 06, 2014 at 04:55 UTC
It isn't nearly finished and is undergoing a transformation since I typed my response, but at the time of this writing you can find the threading code here One of the first things you'll notice is that I didn't implement a "guard" or "doorman". I'm just stuffing everything in the queue for now. Even on directory trees larger than 200GB it barely takes more than 200MB RAM. Tommy A mistake can be valuable or costly, depending on how faithfully you pursue correction	[reply]


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