Il 24/10/2010 20:10, Gennady Kupava ha scritto:
В Вск, 24/10/2010 в 19:34 +0200, Radek Polak пишет:
You wrote:> В Чтв, 21/10/2010 в 22:04 +0200, Radek Polak пишет:
3. i wish 100HZ patch included to qtmoko
(http://www.bsdmn.com/openmoko/kernel/0001-Use-100-as-HZ-value-on-S3C24XX.p
atch)
Oki, i can try, is there any description for the patch? E.g. What does it do
and how can i test it?
It does simple thing - change HZ value of linux kernel from 200HZ to
100HZ. Main reason is performance.
My rationale is following:
Basically this mean that timer interrupts amount will be reduced from
200 per second to 100 per second. This allows:
Pros:
1. Stay more in IDLE state. (less power consumption)
I think that this is something that would be more noticeable with Vasily's
"S3C24xx GENERIC_TIME / GENERIC_CLOCKEVENT support" patch.
2. If several tasks are active, do 2 times less context switches (and
our context switches are expensive). Do not think it will be 'slow'.
This is not applied to all tasks - but only to CPU bound ones.
3. Less interrupts is good on it's own.
Cons:
1. Worse granilarity of delays and sheduled works. I think it's
impossible
2. May reveal some bugs, as any new non-trivial system-wide change.
Basically it works here, but i didn't test everything.
Other arguments:
I checked other boards config files and it turned out that only few of
them (10% or so) using 200 as HZ value.
I did lmbenching and found that difference is few percent, but still
noticeable.
I can't 'feel' that something changed.
Has anyone investigated gathering some data with ftrace? examples start
from line 246.
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/trace/ftrace.txt;h=557c1edeccaf72535464298743cddd3c8eb01bea;hb=HEAD
So, this patch is just sets new value for HZ and changes s3c timer
interrupt frequency.
Wouldn't something like that in arch/arm/Kconfig avoid changes in
arch/arm/plat-samsung/time.c?
default 100 if ARCH_S3C2410
Just asking :)
thanks,
riccardo
