Re: [OE-Core][master][kirkstone][PATCH V2] rng-tools: Add Arm aarch64 CPU specific configuration to address excessive CPU usage on startup

[Xiangyu Chen <xiangyu.chen@windriver.com>]

On 11/7/22 10:18, Khem Raj wrote:
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> On Sun, Nov 6, 2022 at 5:21 PM Xiangyu Chen <xiangyu.chen@windriver.com> wrote:
>>
>> On 11/1/22 09:48, Xiangyu Chen wrote:
>>> With the default jitter options aarch64 CPU-based devices typically experience continuous
>>> high CPU utilisation for several minutes after rngd starts.
>>>
>>> Accoring to the rng-tools issue #150[1] and comments[2],in order to address this,
>>> the following configuration changes have been made, those configurations
>>> also can be found on Alpine Linux[3]:
>>>
>>> - reduce the number of threads used to 1 in total, rather than 1 per core.
>>> - reduce the buffer size from 16535 to 4133 which reduces the time taken
>>>     to fill the buffer (and so reduces the duration of CPU load).
>>>
>>> [1] https://github.com/nhorman/rng-tools/issues/150
>>> [2] https://github.com/nhorman/rng-tools/issues/150#issuecomment-953079212
>>> [3] https://git.alpinelinux.org/aports/tree/main/rng-tools/rngd.confd-arm
>>>
>>> Signed-off-by: Xiangyu Chen <xiangyu.chen@windriver.com>
>>> ---
>>> Changes in V2:
>>>     *put the aarch64 specific default file in meta/recipes-support/rng-tools/rng-tools/aarch64
>> Friendly ping. Is there any more concern on this?
> My concern is that will it be so for all aarch64 machines ?

I tested two aarch64 platforms on my hand, zynqmp and raspi4, the 
rng-tools behavior is the same, when service start, the jitter random 
generator would load full cpu cores load. It would cause other services 
take long time to start. I also checked another linux distribution, so 
far, only Alpine Linux processed this issue and it applied those 
configurations on all aarch64 platforms.


Thanks,

Xiangyu

>
>>
>> Thanks,
>>
>> Xiangyu
>>
>>> ---
>>>    .../rng-tools/rng-tools/aarch64/default               | 11 +++++++++++
>>>    1 file changed, 11 insertions(+)
>>>    create mode 100644 meta/recipes-support/rng-tools/rng-tools/aarch64/default
>>>
>>> diff --git a/meta/recipes-support/rng-tools/rng-tools/aarch64/default b/meta/recipes-support/rng-tools/rng-tools/aarch64/default
>>> new file mode 100644
>>> index 0000000000..5a2fbcc9ef
>>> --- /dev/null
>>> +++ b/meta/recipes-support/rng-tools/rng-tools/aarch64/default
>>> @@ -0,0 +1,11 @@
>>> +# With the default jitter options Arm CPU-based devices typically experience
>>> +# continuous high CPU utilisation for several minutes after rngd starts.
>>> +# See https://gitlab.alpinelinux.org/alpine/aports/-/issues/13035 and
>>> +# https://github.com/nhorman/rng-tools/issues/150
>>> +# In order to address this the following configuration changes have been made:
>>> +#
>>> +#   - reduce the number of threads used to 1 in total, rather than 1 per core.
>>> +#   - reduce the buffer size from 16535 to 4133 which reduces the time taken
>>> +#     to fill the buffer (and so reduces the duration of CPU load).
>>> +#
>>> +EXTRA_ARGS="-r /dev/hwrng -O jitter:buffer_size:4133 -O jitter:refill_thresh:4133 -O jitter:thread_count:1"
>>>
>>>
>>>
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