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    SubjectRe: PROMBLEM: CD burning at 16x uses excessive CPU, although DMA is enabled
    On 8 April 2002 13:47, Anssi Saari wrote:
    > I didn't really know how to put it. Maybe system load would be better. But
    > the actual problem is, I effectively can't burn audio and other types
    > at 16x in Linux, while there is no problem in some other operating systems
    > with the same hardware and applications.
    > Here're some time figures from cdrdao:
    > cdrdao simulate -n --speed 8 foo.cue 2.62s user 3.37s system 1% cpu
    > 6:41.86 total cdrdao simulate -n --speed 12 foo.cue 2.78s user 29.91s
    > system 12% cpu 4:31.71 total cdrdao simulate -n --speed 16 foo.cue 2.67s
    > user 128.77s system 52% cpu 4:10.68 total
    > So yes, system time goes up quite steeply.
    > But even though 50% is quite high, CPU load is not the problem as such,
    > the problem is getting data to the writer fast enough. And it's not
    > happening. Even a single audio track that is completely cached so that
    > there is no HD access has problems. It's like somehow accessing the CD
    > writer hogs the system for such long periods that there is insufficient
    > time to fill the writing program's buffer.

    You may try profiling kernel to see where it exactly spending that time.
    It has an added benefit: you will learn how to profile kernels (if you
    don't know how to do it already).

    I am waiting for similar problem to bite me to learn that, too. :-)

    > One thing I noticed just now. If I turn off unmaskirq for the CD writer
    > with hdparm -u 0 /dev/hdc, it helps a little, but not enough. Time
    > reports now:
    > cdrdao simulate -n --speed 16 foo.cue 2.75s user 75.18s system 58% cpu
    > 2:13.22 total
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