Re: [Gumstix-users] 1-ms jiffy?

[Herve L. <Herve.Lacheray@Quanser.com>]

I actually edited the "linux-*/arch/arm/Kconfig" file to change HZ =
default from 100 and 1000 and that set CONFIG_HZ in" linux-*/.config" to =
1000 during the build.

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So now, even though CLOCK_REALTIME has a resolution of 1 msec, for =
example nanosleep only returns every 2 msec; I am wondering why...

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Also does anyone know what the upper limit is for the system clock =
resolution? Is it: CONFIG_HZ =3D 1535?=20

Or would it be another way to get a finer system clock resolution?

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Thanks a lot,

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Herv=E9

________________________________

From: gum...@li... =
[mailto:gum...@li...] On Behalf Of =
Heilpern, Mark
Sent: Monday, November 19, 2007 12:14 PM
To: General mailing list for gumstix users.
Subject: Re: [Gumstix-users] 1-ms jiffy?

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The CONFIG_HZ setting is getting overwritten when you build your kernel; =
the overwrite setting is somewhere inside your buildroot/target =
directory.

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To find it, cd to target and issue this command: "find . -name =
\*config\* | xargs grep CONFIG_HZ" (without the quotes). On my system =
(older than 1553 but I don't know the version), I see the following as =
output from that command:

./device/Gumstix/basix-connex/linux.config:CONFIG_HZ=3D100

./device/Gumstix/basix-connex/.svn/text-base/linux.config.svn-base:CONFIG=
_HZ=3D100

./device/Gumstix/verdex/linux.config:CONFIG_HZ=3D100

./device/Gumstix/verdex/.svn/text-base/linux.config.svn-base:CONFIG_HZ=3D=
100

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Making the appropriate change (in =
target/device/Gumstix/basix-connex/linux.config, for your connex) should =
propagate into the kernel build.

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________________________________

From: gum...@li... =
[mailto:gum...@li...] On Behalf Of Herve =
Lacheray
Sent: Friday, November 16, 2007 4:53 PM
To: gum...@li...
Subject: [Gumstix-users] 1-ms jiffy?

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Hi everyone,

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Is it still possible to set the gumstix's system clock from 10 to 1 =
millisecond?

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I changed the HZ value from 100 to 1000 in the =
build_arm_nofpu/linux-*/include/asm-arm/param.h file, as described here:

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http://docwiki.gumstix.org/Tips_and_tricks#Change_Timer.2FScheduler_Frequ=
ency

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but that did not work. I have a Connex 400MHz and I am using buildroot =
revision #1553.

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I also changed the CONFIG_HZ value from 100 to 1000 in the Linux kernel =
.config file but that got reverted back to 100 during the build =
process...

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Thanks in advance for your help,

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Herv=E9

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