Hi everyone:
I want change the "CONFIG_HZ" to 1000 for my CPU. These are my CPU information,
root@familiar:~# cat /proc/cpuinfo
processor : 0
model name : ARM926EJ-S rev 5 (v5l)
BogoMIPS : 91.13
Features : swp half thumb fastmult edsp java
CPU implementer : 0x41
CPU architecture: 5TEJ
CPU variant : 0x0
CPU part : 0x926
CPU revision : 5
Hardware : Atmel AT91SAM9
Revision : 0000
Serial : 0000000000000000
But when I change my .config which is based on "at91_dt_defconfig". I can't change the "CONFIG_HZ" to 1000, it is still 128. Because the "CONFIG_SOC_AT91RM9200" is 'y'. My questions are:
1. What is better value for "CONFIG_HZ" when I enable "CONFIG_HIGH_RES_TIMERS" for my hardware board?
2. Can I disable the "CONFIG_SOC_AT91RM9200" for my hardware board ?
3. Can I change the "CONFIG_HZ" to 1000 ?
Can someone give me some information? Thanks.
Note: When the HZ is 128, the CPU loading average is bigger 2.(08:51:44 up 30 min, 1 user, load average: 2.56, 2.64, 2.32)
When I change the HZ to 1000, the CPU loading average is lower 1 (08:41:17 up 1:55, 1 user, load average: 0.99, 0.85, 0.77)
How to change the "HZ_FIXED" when "CONFIG_HIGH_RES_TIMERS" is 'y'
Moderator: nferre
- blue_z
- Location: USA
Post
The AT91RM9200 SoC has an ARM920T processor (ARMv4T), and not an ARM926EJ-S (ARMv5).
You should only enable this CONFIG_SOC_AT91RM9200 if you are actually using an AT91RM9200.
What SoC are you using?
What Linux kernel version are you using?
What makes you think high-resolution timers are related?
What are you specifically trying to achieve?
Regards
Re: How to change the "HZ_FIXED" when "CONFIG_HIGH_RES_TIMERS" is 'y'
Duh, that doesn't correlate.pakydu wrote:These are my CPU information,
...
model name : ARM926EJ-S rev 5 (v5l)The
...
Because the "CONFIG_SOC_AT91RM9200" is 'y'.
The AT91RM9200 SoC has an ARM920T processor (ARMv4T), and not an ARM926EJ-S (ARMv5).
You should only enable this CONFIG_SOC_AT91RM9200 if you are actually using an AT91RM9200.
What SoC are you using?
What Linux kernel version are you using?
Exactly how are you doing this?pakydu wrote:But when I change my .config ...
Instead of summations, describe exactly what you are doing, and the results you see, not your interpretations.pakydu wrote:I can't change the "CONFIG_HZ" to 1000, it is still 128.
"Better" than what? Using what criteria?pakydu wrote:1. What is better value for "CONFIG_HZ" when I enable "CONFIG_HIGH_RES_TIMERS" for my hardware board?
What makes you think high-resolution timers are related?
If you board doen't have an AT91RM9200, then there never was a reason to specify it in the first place.pakydu wrote:2. Can I disable the "CONFIG_SOC_AT91RM9200" for my hardware board ?
Why?pakydu wrote: 3. Can I change the "CONFIG_HZ" to 1000 ?
What are you specifically trying to achieve?
Regards
Post
Re: How to change the "HZ_FIXED" when "CONFIG_HIGH_RES_TIMERS" is 'y'
blue_z wrote: ↑Thu Mar 22, 2018 1:51 amDuh, that doesn't correlate.pakydu wrote:These are my CPU information,
...
model name : ARM926EJ-S rev 5 (v5l)The
...
Because the "CONFIG_SOC_AT91RM9200" is 'y'.
The AT91RM9200 SoC has an ARM920T processor, and not an ARM926EJ-S.
You should only enable this CONFIG_SOC_AT91RM9200 if you are actually using an AT91RM9200.
What SoC are you using?
What Linux kernel version are you using?Paky: I am using SOC "AT91SAM9260B". My kernel is 4.4.57. So I thing I just need enable "CONFIG_SOC_AT91SAM9", not need "CONFIG_SOC_AT91RM9200". Is it correct ?Exactly how are you doing this?pakydu wrote:But when I change my .config ...Instead of summations, describe exactly what you are doing, and the results you see, not your interpretations.pakydu wrote:I can't change the "CONFIG_HZ" to 1000, it is still 128.
paky: My old .config enable "CONFIG_SOC_AT91RM9200", so the HZ is 128. My user processes has a high CPU loading.(Such as: 09:23:38 up 1:02, 1 user, load average: 2.75, 2.79, 2.70). I can't find what is wrong on my user space code. So I try to change the HZ."Better" than what? Using what criteria?pakydu wrote:1. What is better value for "CONFIG_HZ" when I enable "CONFIG_HIGH_RES_TIMERS" for my hardware board?
What makes you think high-resolution timers are related?paky: So I want to fine tune the HZ value to try to fix the CPU loading issue. When I disable "CONFIG_SOC_AT91RM9200", and change the HZ to 1000. the CPU loading goes down.(such as: 13:32:06 up 1:55, 1 user, load average: 1.18, 1.31, 1.34)If you board doen't have an AT91RM9200, then there never was a reason to specify it in the first place.pakydu wrote:2. Can I disable the "CONFIG_SOC_AT91RM9200" for my hardware board ?
Paky: Understand. Thanks.
Why?pakydu wrote: 3. Can I change the "CONFIG_HZ" to 1000 ?
What are you specifically trying to achieve?Regardspaky: So I want to fine tune the HZ value to try to fix the CPU loading issue. When I disable "CONFIG_SOC_AT91RM9200", and change the HZ to 1000. the CPU loading goes down.(such as: 13:32:06 up 1:55, 1 user, load average: 1.18, 1.31, 1.34)
- blue_z
- Location: USA
Post
Re: How to change the "HZ_FIXED" when "CONFIG_HIGH_RES_TIMERS" is 'y'
Your response is unreadable because you're misusing quote tags.
I have no expertise with load averages, but AFAIK load averages when using different HZ are not comparable.
The load average is related to the tick duration, so simply increasing the HZ will always reduce the load average.
So your comparison of load averages is like comparing apples versus oranges.
IOW you're using a bogus metric, and your goal of increasing HZ is misguided.
Regards
I have no expertise with load averages, but AFAIK load averages when using different HZ are not comparable.
The load average is related to the tick duration, so simply increasing the HZ will always reduce the load average.
So your comparison of load averages is like comparing apples versus oranges.
IOW you're using a bogus metric, and your goal of increasing HZ is misguided.
Regards
Post
Re: How to change the "HZ_FIXED" when "CONFIG_HIGH_RES_TIMERS" is 'y'
Thank you, blue_z.
I know your mean, but I have one question: how to get a correct HZ for a system? ( What should we do when we config a new kernel for HZ? )
Thanks again.
I know your mean, but I have one question: how to get a correct HZ for a system? ( What should we do when we config a new kernel for HZ? )
Thanks again.
- blue_z
- Location: USA
Post
Since you have presented no compelling reason, the sensible value for HZ would be the default value.
Be aware that increasing the value of HZ has a cost, i.e. increased overhead, with dubious benefit.
Whereas there are other kernel configuration options that are specifically targeted at effectively improving performance of userspace programs (e.g. preemptible kernel, alternate memory allocators, and alternate I/O schedulers).
However without analyzing your system and processes, you're just guessing at what should be changed.
Regards
Re: How to change the "HZ_FIXED" when "CONFIG_HIGH_RES_TIMERS" is 'y'
Is this a case of bad spelling or bad grammar?pakydu wrote:I know your mean,...
Your question is unreasonable, since there is no single "correct" value for HZ.pakydu wrote:... but I have one question: how to get a correct HZ for a system?
Since you have presented no compelling reason, the sensible value for HZ would be the default value.
Be aware that increasing the value of HZ has a cost, i.e. increased overhead, with dubious benefit.
Whereas there are other kernel configuration options that are specifically targeted at effectively improving performance of userspace programs (e.g. preemptible kernel, alternate memory allocators, and alternate I/O schedulers).
However without analyzing your system and processes, you're just guessing at what should be changed.
Regards
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