[DUG] Memory allocation speed

[Ross Levis]

Your probably right.  That makes sense.

 

It's certainly easier to code than using static blocks and reusing them.

 

From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz] On
Behalf Of Rohit Gupta
Sent: Friday, 24 September 2010 12:48 PM
To: NZ Borland Developers Group - Delphi List
Subject: Re: [DUG] Memory allocation speed

 

I think that because your chunk size is constant, the memory manager just
returns previous blocks to you.  So fragmentation does not occur.

On 24/09/2010 01:52, Ross Levis wrote: 

Just wanted some opinions on how bad a practice this is!

 

I have written a media player which uses a DLL to decode audio files.

 

The DLL opens an MP3 file for example, and sends back decoded raw audio,
usually in chunks of 4608 bytes (~20ms), but could be a different size.

 

I need to buffer this audio data for around 5 seconds (1 MB).

 

Rather than writing a complicated circular buffer which feeds in one end and
is taken from the other, I decided to simply allocate memory for each new
chunk and store a link from one memory location to the next.  The oldest
buffer is read and memory released.

 

So there is roughly 1 new memory space being allocated and 1 being destroyed
every 20ms or so, with around 200 chunks being stored at any one time.

 

I'm using D7 with the FastMM4 memory manager.

 

It is working very well with very little CPU usage at all, which I was
surprised at.  I've always been under the impression that allocating memory
is a slow process.

 

Thoughts?



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Regards

Rohit Gupta
B.E. Elec., M.E., Mem IEEE, Member IET
Technical Manager
Computer Fanatics Ltd

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