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SubjectRe: PROMBLEM: CD burning at 16x uses excessive CPU, although DMA is enabled
Date
On tisdagen den 9 april 2002 12.01, Anssi Saari wrote:
> On Mon, Apr 08, 2002 at 06:02:55PM -0400, Mark Hahn wrote:
> > I think someone else already pointed out that doing
> > a kernel profile would be good. strace would also
> > be quite useful, even just the -c form.
>
> Here it is:
>
> With unmaskirq=1 first:
>
>
> 49 handle_IRQ_event 0.5104
> 239 file_read_actor 2.4896
> 3324 default_idle 69.2500
> 20097 ide_output_data 104.6719

Hey, what is this?

Comment of the function is:
"This is used for most PIO data transfers *to* the IDE interface"
(see /drivers/ide/ide.c:426)
Has it reverted to PIO mode?

Some information might be found with
# more /proc/ide/hd*/settings

This is how mine look like
cat /proc/ide/hdc/settings
name value min max mode
---- ----- --- --- ----
bios_cyl 0 0 1023 rw
bios_head 0 0 255 rw
bios_sect 0 0 63 rw
current_speed 66 0 69 rw
ide_scsi 0 0 1 rw
init_speed 66 0 69 rw
io_32bit 0 0 3 rw
keepsettings 0 0 1 rw
log 0 0 1 rw
nice1 1 0 1 rw
number 2 0 3 rw
pio_mode write-only 0 255 w
slow 0 0 1 rw
transform 1 0 3 rw
unmaskirq 1 0 1 rw
using_dma 1 0 1 rw

> 23952 total 0.0236
> Number of interrupts on ide1 during burn: 17531
>
> And then, unmaskirq=0:
>
> - - -
> 168 do_softirq 0.9545
> 234 file_read_actor 2.4375
> 1942 handle_IRQ_event 20.2292
> 2949 default_idle 61.4375
> 6808 ide_intr 18.5000
> 12333 total 0.0122
> Number of interrupts on ide1 during burn: 17532

This looks like mine results. Quite some time spent in interrupt
routines. (weighted 38%)
Using or not using unmaskirq does not matter for me:
It stays below 40%, but I do only run at 10x (40% is quite much
for any disk bound operation...)

I will attempt a profiling while unmasked too.

I assume you also use ide_scsi, right?

/RogerL

--
Roger Larsson
Skellefteå
Sweden

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