On Sun, Dec 16, 2007 at 01:31:11AM +0000, brian m. carlson wrote:
> On Sat, Dec 15, 2007 at 08:10:04PM +0100, Sjoerd Simons wrote:
>> On Thu, Dec 13, 2007 at 10:21:06PM +0100, Michael Biebl wrote:
>>> > [0] I suspect it is 10 times a second, because that's the number of
>>> > libata wakeups I see, but I haven't actually checked.
>>>
>>> Hal polls the CD drive every 2 seconds afaik.
>>
>> Hal indeed polls every 2 seconds at most and even less when something hints
>> hal
>> that nobody the machine is idle.
>
> hald-addon-storage claims it is polling every two seconds:
>
> lakeview ok % ps ax | grep hald-addon-storage
> 3600 ? S 0:06 hald-addon-storage: polling /dev/scd0 (every 2 sec)
>
>> Could you strace the running hald-addon-storage to check if indeed it's
>> polling
>> your drive multiple times a second ?
>
> Output of strace:
>
> open("/dev/scd0", O_RDONLY|O_EXCL|O_NONBLOCK) = 5
> ioctl(5, CDROM_DRIVE_STATUS, 0x7fffffff) = 2
> close(5) = 0
> poll([{fd=3, events=POLLIN}], 1, 1981) = 0
> poll([{fd=3, events=POLLIN}], 1, 0) = 0
> open("/dev/scd0", O_RDONLY|O_EXCL|O_NONBLOCK) = 5
> ioctl(5, CDROM_DRIVE_STATUS, 0x7fffffff) = 2
> close(5) = 0
> poll([{fd=3, events=POLLIN}], 1, 1980) = 0
> open("/dev/scd0", O_RDONLY|O_EXCL|O_NONBLOCK) = 5
> ioctl(5, CDROM_DRIVE_STATUS, 0x7fffffff) = 2
> close(5) = 0
> poll([{fd=3, events=POLLIN}], 1, 1981) = 0
> poll([{fd=3, events=POLLIN}], 1, 0) = 0
> open("/dev/scd0", O_RDONLY|O_EXCL|O_NONBLOCK) = 5
> ioctl(5, CDROM_DRIVE_STATUS, 0x7fffffff) = 2
> close(5) = 0
> poll([{fd=3, events=POLLIN}], 1, 1981) = 0
> poll([{fd=3, events=POLLIN}], 1, 0) = 0
>
> Is it possible that opening and closing the drive is causing the wakeups?
> I ask because I'm seeing 10 libata wakeups and about 10
> "rescheduling interrupts" wakeups whenever hal is polling:
strace -tt would be more usefull as that outputs timing information. The
open,ioctl,close triple will cause various wakeups every two seconds.. But only
in a short time, so that shouldn't have a big impact on the time your processor
can actually spent in a lower power state.
Polling is indeed not a great thing to do, but unfortunately cd drivers don't
appear to have a nice way to notify media insertion.
Sjoerd
--
No amount of careful planning will ever replace dumb luck.
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