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Re^2: Perl threading stability?

by guice (Scribe)
on Jul 25, 2005 at 17:59 UTC ( #477927=note: print w/ replies, xml ) Need Help??


in reply to Re: Perl threading stability?
in thread Perl threading stability?

Now this part surpises me:

Shared data in perl's ithreads is very expensive, both in terms of speed and memory usage. A shared scalar variable usually has a copy in every thread that uses it, plus a separate shared copy. When you assign to a scalar, the thread's copy is updated, then that data is also copied to the hidden shared copy. When you read from a shared scalar, the data from the hidden shared copy is copied to the thread's one. Thus if you have N threads all accessing a long string variable, your memory usage will tend towards (N+1) times the length of the string.

I would have thought Perl use references for everything, not complete copies, making things much less memory and resource intensive...

Try to avoid having complex, deeply-nested shared data structures

Doh! One of the ideas was to use an XML::Simple object to store server data and each thread would update that object based on possible changes ... looks like I might have to keep with fork() with a slight restructure in how i would modify that main hash.

-- philip
We put the 'K' in kwality!


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