Messages in this thread |  | | Date | Fri, 30 Aug 2002 13:39:13 +0200 | From | Frank Otto <> | Subject | Re: PROBLEM: conflict between apm and system clock on Inspiron 8100 |
| |
Hi Stephen,
On Thu, Aug 29, 2002 at 12:11:03PM +1000, Stephen Rothwell wrote: > > Interesting ... Howlong does "cat /proc/apm" take? > On my Thinkpad T22 I get: > > # time cat /proc/apm > 1.16 1.2 0x03 0x01 0x00 0x01 99% -1 ? > > real 0m0.009s > user 0m0.000s > sys 0m0.010s
On my Thinkpad R32, the timings vary:
real: anything between 15ms and 40ms user: mostly 0ms, sometimes 10ms sys: mostly 20ms, sometimes 30ms
To get average values, I did this:
blackmagic:~> time for i in `seq 1 600`; do cat /proc/apm >/dev/null; done
real 0m14.775s user 0m0.700s sys 0m12.650s
However, these values are rather bogus; I also measured the time with my digital wristwatch. Result: 60.60s ====== To measure the overhead of the shell command itself, I did this:
blackmagic:~> cat /proc/apm >/tmp/apm blackmagic:~> time for i in `seq 1 600`; do cat /tmp/apm >/dev/null; done
real 0m1.769s user 0m0.900s sys 0m0.690s
For the sake of simplicity, this overhead can be neglected. So: reading /proc/apm 600 times roughly takes 60 real seconds, which means that reading it once takes about 100ms. This is huge, isn't it?
BTW, I tried this both with apm_allow_ints enabled and disabled. Didn't make much difference. (And my Thinkpad didn't hang after the BIOS calls with apm_allow_ints disabled, so maybe IBM has fixed a bug? By introducing another one ;-)
I think I haven't mentioned yet that I'm using a vanilla 2.4.19 kernel.
> while ... > > # time ./tppow > Battery 0 present power units mW[h] design capacity 38880 last full charge capacity 29260 > status 0x0 rate 0 cap 29172 voltage 12485 > > real 0m0.311s > user 0m0.100s > sys 0m0.000s > > tppow is a C implementation of the disassembled APCI method for reading the > battery status. It does not disable interrupts but does talk to the > embedded controller in the Thinkpad.
Interesting. Where can I get `tppow'? Would it even be safe to use it on a different Thinkpad?
Thanks, Frank - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |