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

[Paul K. <pko...@au...>]

Ciao Luca,

Thanks for the HZ test. I tried it on two linux boxes, one with =
HZ=3D1000
running 2.4.18-gensched and the other running RHL 7.3.

I typed:

./jittertest -r

It looks like RML's HZ patch works ok with HZ=3D1000 (as he maintains); =
in
Res.txt the third column has numbers close to 1.=20

On the RHL 7.3 box, Res.txt has numbers around 10-18.

Regards,=20

Paul Koufalas
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-----Original Message-----
From: Luca Abeni [mailto:luc...@em...]=20
Sent: Wednesday, August 27, 2003 7:20 PM
To: lin...@li...
Cc: Paul Koufalas
Subject: Re: Changing HZ from 100 to 500 or 1000


Hi Paul,

> We tried this 2 ways:
>
> 1. Using Robert Love's patch:=20
> variable-hz-rml-2_4_20-pre10-ac2-1_patch.text
> applied to a 2.4.18 kernel (no rejects occurred)
>=20
> 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.
>=20
> Is there a way to check if the change is in effect? Ie,=20
> 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=3D1000, the third
column should contain values around 1.0

> On the other hand, if we didn't setup up res1 parameters Amount and=20
> 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 =3D 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.
--=20
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