3 Oct
2007
3 Oct
'07
6:46 p.m.
On Wednesday 03 October 2007, Frank Barknecht wrote:
Generally we have two kinds of kernels: The
"vanilla" kernel as
downloadable on kernel.org and the same kernel, but patched with Ingo
Molnars RT-patches. The vanilla kernel, if configured properly with
CONFIG_PREEMPT etc., already gives very good performance in the low
latency department, enough for many users, even audio users. I run one
of these.
Well, the vanilla kernel also has a CONFIG_HZ setting of i think 200hz per
default. This is too little timing resolution for processes that rely on the
system timer frequency being higher [some sequencers come to mind]..
The "lowlatency" kernel in ubuntu thus has CONFIG_HZ set to 1000 and
CONFIG_PREEMPT enabled.
This might be good enough for some people..
For a truly reliable system (where you can count on no audio period being
missed because you forgot to disable the damn updatedb cronjob) you need a
system patched with ingo's realtime preemption patches and have it properly
configured. E.g. situations where you record performances that are not
repeatable.. Or you cannot afford to have a click because your signal goes
over a 100000 Watt P.A. [Though i guess with vanilla jack you must not change
any connections during the task because this might cause lost buffers [due to
vanilla jackd doing some coarse grained locking], too - jackdmp might help]..
Regards,
Flo
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