[LAD] jackd buffersize

Paul Davis paul at linuxaudiosystems.com
Mon May 11 15:29:26 UTC 2009

On Mon, May 11, 2009 at 11:21 AM, Jens M Andreasen
<jens.andreasen at comhem.se> wrote:
> On Mon, 2009-05-11 at 10:23 -0400, Paul Davis wrote:
>> 1) the question is now how to fit a single set of N samples into cache
>> memory. Its how to fit *all* the samples to be processed in a given
>> "cycle" into cache memory. Wasting 25% of cache memory for each buffer
>> isn't conducive to this.
> If 96 frames are enough for stability (and say 64 isn't), then sample 96
> - 127 in a 128 frame buffer are a waste of memory anyway and only adds
> to latency.

sometimes there is a tradeoff between latency and CPU cycles. live
recording often tilts towards less CPU cycles and more latency.

> It may even be so that a set of shorter buffers that are only partially
> aligned - but allocated as one continous area - may have a greater
> chance of fitting into available cache, without trashing other important
> data.

the point of making things cache aligned relates to SSE(2). the point
of making them fit in the cache relates to overall throughput. not
quite the same thing.

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