ATAPI CD-R lags system to hell burning in DAO mode; but not in TAO

ATAPI CD-R lags system to hell burning in DAO mode; but not in TAO

[Aaron Lehmann]

I've got a Teac CD-W524E 24x CD-R writer, and ever since I got it
several months ago I have had the somewhat annoying issue that burning
a cd Disc-At-Once makes the system unusable during the burn. The X
cursor jerks, repaints take forever, etc. This problem doesn't occur
when burning Track-At-Once - I'm unable to notice any significant
increase in system latency when using that mode.

The burner is the only IDE device in the system, and it is the primary
master on the primary IDE controller, which is a SiS 5513. It's in
UDMA2 mode. I'm using ide-scsi emulation, of course. All 2.4 kernels
that I have tried exhibit this problem, including 2.4.17 and
2.4.18-ac3. It does not matter whether I burn with cdrdao or with
cdrecord -dao - both lag the system like crazy. I noticed that turning
on 32-bit I/O with hdparm helps immensely. This reduces the lag
significantly. Setting unmaskirq seems to help a lot too. However, I'm
still not satisfied. In particular, burning over NFS in DAO mode is
not practical (the data rate simply can't be sustained), even though I
can burn TAO CDs fine over NFS.

My friend has a Plextor PX-W2410A burner with similar specifications,
and it has the same symptoms as I do. I believe he has a VIA IDE
chipset.

I'd like to know if there's a workaround for the problem, and if not,
what tools and/or methods I can use to track down the source of the
noninteractivity so that a kernel hacker can fix it. The machine has
half a gigabyte of RAM, never swaps, and reports 2916.35 bogomips. I
think it should be able to burn CDs without too much sweat.

Re: ATAPI CD-R lags system to hell burning in DAO mode; but not in TAO

[Andrew Morton]

Aaron Lehmann wrote:
> 
> I've got a Teac CD-W524E 24x CD-R writer, and ever since I got it
> several months ago I have had the somewhat annoying issue that burning
> a cd Disc-At-Once makes the system unusable during the burn. The X
> cursor jerks, repaints take forever, etc. This problem doesn't occur
> when burning Track-At-Once - I'm unable to notice any significant
> increase in system latency when using that mode.
> 

This is presumably because the machine is full of memory which
is dirty against a slooow device.

You can work around this by reducing the dirty memory thresholds:

akpm-1:/home/akpm> cat /proc/sys/vm/bdflush
30      64      64      256     30000   3000    60      0       0

Make the "30" and "60" smaller.  10 and 20 perhaps.

Better: change the application to fsync() the data every few
megabytes, or open O_SYNC.

-

Re: ATAPI CD-R lags system to hell burning in DAO mode; but not in TAO

[Aaron Lehmann]

On Wed, Jul 31, 2002 at 02:05:30PM -0700, Andrew Morton wrote:
> This is presumably because the machine is full of memory which
> is dirty against a slooow device.

I don't seem to have sysctl support in my kernel right now, so I can't
verify this until I reboot.

I did notice that both cdrdao and cdrdao set realtime scheduling
priority. I thought this would surely answer everything, but burning
as an unprivileged user causes the same interactvity (and NFS
throughput) problems as before.

Re: ATAPI CD-R lags system to hell burning in DAO mode; but not in TAO

[DervishD]

    Hi Aaron :)

>My friend has a Plextor PX-W2410A burner with similar specifications,
>and it has the same symptoms as I do. I believe he has a VIA IDE
>chipset.

    I have a Plextor 12/10/32 (just a bit newer) with a VIA chipset
on the mobo, and the only thing that is affected when burning DAO is
X Window. I've made a little test: compiling three kernels 2.4.18 and
playing the burned files while burning at 12x in DAO runs smoooooth.
In fact, I haven't noticed the test finish since the performance was
almost the same. But X freezes.

    IMHO it's a problem of X, not kernel :?? FYI I have 512M of RAM
and a Duron 850 (over 1700-1800 bogomips).

    Raúl

Re: ATAPI CD-R lags system to hell burning in DAO mode; but not in TAO

[Anssi Saari]

On Wed, Jul 31, 2002 at 01:30:08PM -0700, Aaron Lehmann wrote:
> I've got a Teac CD-W524E 24x CD-R writer, and ever since I got it
> several months ago I have had the somewhat annoying issue that burning
> a cd Disc-At-Once makes the system unusable during the burn. The X
> cursor jerks, repaints take forever, etc. This problem doesn't occur
> when burning Track-At-Once - I'm unable to notice any significant
> increase in system latency when using that mode.
 
I've been having a similar problem, but in my case it's audio and other
non-data CD writes like VCD that have this kind of slowdown problem.
DAO vs. TAO doesn't matter in my case. IDE chipset is VIA 686b. The
problem disappears if I plug the writer to onboard pdc20265, but burns
on that are otherwise flaky.