Peter Jeremy wrote:
On Sun, 2006-Aug-27 16:37:29 -0700, Jin Guojun [VFFS] wrote:
I have difficulty to get CD/DVD write speed above 1.6MB/s (10x for CD,
or 1.1x for DVD).
The problem seems to be the interrupt rate is high (70-80% of CPU) for
CD/DVD drive(r).
Your drive is probably in PIO4 mode (due to there being bugs in the
UDMA implementation on many drives). Check hw.ata.atapi_dma and
"atacontrol mode acd0". You may find you can change to WDMA2 mode
which will significantly reduce the interrupt and CPU load. You will
need to do some experimenting with your drives to see what works for
you.
Yes, this is the problem.
hw.ata.atapi_dma=1
but 6.1-R configures acd0 to PIO4.
"atacontrol mode acd0 WDMA2" makes acd0 into correct mode.
Under 4.11-R, things are complicated.
hw.ata.atapi_dma=1 makes boot process configure acd0 to UDMA2,
but Tx (I/O) rate limits at 1.6 MB/s. atacontrol will not help.
hw.ata.atapi_dma=0 makes boot process configure acd0 to PIO4,
and initial Tx rate is 1.6 MB/s. However, use atacontrol to change
mode to WDMA2, or UDMA2, or back to PIO4, Tx rate can go up
for a single I/O session or more , but not stable. In random time,
the Tx rate will drop back to 1.6 MB/s.
Since 6.1-R works, I would not think we need to worry about 4.11-R
for this issue.
Thanks for the information,
-Jin
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