[Linux-hls-devel] Re: Changing HZ from 100 to 500 or 1000

[Luca A. <luc...@em...>]

Hi Paul,

> We tried this 2 ways:
>
> 1. Using Robert Love's patch:
> variable-hz-rml-2_4_20-pre10-ac2-1_patch.text
> applied to a 2.4.18 kernel (no rejects occurred)
> 
> 2. Hard coding HZ in include/asm/param.h
Both the two ways should work ok, but the first one is "more correct",
because is does not screw some statistics in the procfs.

> Neither seemed to make much of a difference.
> 
> Is there a way to check if the change is in effect? Ie,
> measure/estimate HZ from /proc or elsewhere?
I think the best way is to measure it from user space (for example, by
setting an itimer with period 1ms, and checking how oftern the timer
signal is triggered).
I attach a program that does something similar. It sets an itimer at
1000us, but on a standard kernel the real period will be 10ms (see the
third column in Res.txt). With HZ=1000, the third column should contain
values around 1.0

> On the other hand, if we didn't setup up res1 parameters Amount and
> Period using the correct units, we would expect to be dropping/missing
> frames in our application.
I suspect this can be the reason... A full dmesg output would be useful.

> Were you able to confirm that 1 unit = 100ns?
I still have to check to be 100% sure, but I think it is 100ns. I'll
check this evening.

				Luca

P.S.: I sent the previous mail to the wrong list... This
(lin...@li...) is the correct one. Sorry for
the confusion.
-- 
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