26 Jan
2007
26 Jan
'07
8:40 p.m.
On 1/26/07, Florian Schmidt <mista.tapas(a)gmx.net> wrote:
The value in /proc/sys/dev/rtc/max-user-freq
determines to what maximum
frequency ordinary users can set the RTC. You usually want to have your app
decide that, so set it to 8192, so the app can use whatever freq it wishes.
That default of 64HZ is ancient. From Documentation/rtc.txt:
"Just for reference, a typical 486-33 running a tight read loop on
/dev/rtc will start to suffer occasional interrupt pileup (i.e. > 1 IRQ
event since last read) for frequencies above 1024Hz. So you really
should check the high bytes of the value you read, especially at
frequencies above that of the normal timer interrupt, which is 100Hz.
Programming and/or enabling interrupt frequencies greater than 64Hz is
only allowed by root. This is perhaps a bit conservative, but we don't want
an evil user generating lots of IRQs on a slow 386sx-16, where it might have
a negative impact on performance. Note that the interrupt handler is only
a few lines of code to minimize any possibility of this effect."
;-)
I wrote a patch to increase the default to 1024HZ but never submitted
it. I'll try to dig it up...
Lee