Subject: [linux-audio-dev] low latency 2.2.17 RPMs available (parport causing high latencies ?)
From: Benno Senoner (sbenno_AT_gardena.net)
Date: Tue Sep 19 2000 - 19:38:03 EEST
Hi all ,
(Andrea & Tim, please read the stuff about the parport.
(parport perhaps causing high latencies, what do you think ?))
new 2.2.17-low-latency kernel RPMs are available:
(basically a 2.2.17 patched with Ingo's 2.2.16-LL patch).
http://www.gardena.net/benno/linux/lowlatency-rpm.html
Notice that I was wrong with the performance of 2.2.15:
it shows just up the same peaks as in 2.2.16 and 2.2.17
so I would not use buffersizes below 3x256 (4.5msec latencies)
That means the winner is still 2.2.10+lowlatency (reliable 2.1msec latency)
But 2.4.0-test7-LL seems to work even better but it's not 100% stable yet
(or as Ingo said ,the disk sync code needs some speedup)
Plus during the last days some additional stresstests while printing:
I ran latencytest on 2.2.17-LL , but while printing out a large PDF
via parallel printer:
And I registered a two 6msec peaks on this kernel :-(
Perhaps it is due to the polled printer driver ?
I have never seen that peak before.
(But who says that you must print while performing low latency
audio ? :-) )
(does anyone know if linux supports DMA on the parallel port
(perhaps this will help),
and if it's enough to enable this in the BIOS ?)
I recall my experiences with PLIP ( a P133 connected via
PLIP (IP over parallel port) to a 486.
When the 486 was transfering data (a large FTP or running
X11 over the parallel port), the Pentium box almost stalled
and slowed to a crawl, so I think that the latency peaks
are probably caused by the parallel port.
cheers,
Benno.
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