linuxaudio.org

On Wed, Sep 9, 2009 at 11:45 PM, James Cameron  wrote:

quoted text
> Yes, the ideal is that the tracks being played are cached in RAM so that

> no disk access is required.  The recording track would be creating a

> file that would be periodically written to disk.

this is not the ideal. its how any serious recording application has

to work. Linux filesystems can stall a thread for seconds while doing

disk i/o. you cannot do disk i/o from the thread that handles incoming

audio unless you already buffered like crazy.
ardour has a buffer of about 5 seconds, per channel, per direction

(its user configurable). both playback and recording occurs via these

buffers. ardour also tries to read/write in blocks of 256kB, since at

one point we empirically determined that this maximized disk

throughput in many cases. in an ideal world, we'd probably use O_RAW

for file i/o, and thus bypass the duplicated buffering of the kernel

FS buffer cache. but for now, that extra layer of buffering serves us

quite well (especially for read-ahead), and so we don't bother with

that.

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