Re: [dpdk-dev] running dpdk application on the same machine with other none dpdk application

[Shirley Avishour <shirley@imvisiontech.com>]

Hi Rami,
Thanks for the quick reply. So in fact there is no way to tell the kernel
not to run kernel threads on specific cpus?
Even not by compiling the kernel with specific flags?
Do you know if the PF_NO_SETAFFINITY flag can help in any way?

Thanks,
Shirley.


On Wed, Jan 30, 2019 at 9:26 AM Rami Rosen <ramirose@gmail.com> wrote:

> Hi Shirley,
>
> I think you are right, isolcpus is for userspace threads.
> ...
> "Use the isolcpus parameter on the kernel command line to isolate certain
> cores from user-space tasks."
> ...
> See:
>
> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/performance_tuning_guide/sect-red_hat_enterprise_linux-performance_tuning_guide-cpu-configuration_suggestions
> So if there is no way to configure JVM to use specified kernel cores (and
> I am afraid there is no such way),
> I am not sure how this can be solved.
>
> Regards,
> Rami Rosen
>
>
> On Wed, Jan 30, 2019 at 9:05 AM Shirley Avishour <shirley@imvisiontech.com>
> wrote:
>
>> Hi Rami,
>>
>> This is the printout for cat /proc/cmdline
>> BOOT_IMAGE=/boot/vmlinuz-4.15.0-43-generic
>> root=UUID=6f1a210b-a30f-456d-bf16-bbb210da5666 ro default_hugepagesz=2M
>> hugepagesz=2M hugepages=4096 isolcpus=1-5 nohz_full=1-5 rcu_nocbs=1-5
>>
>> The requires cpus are in fact isolated but jvm generate some kernel
>> threads as well and I'm afraid that these kernel space threads eventually
>> use all cores. isolcpus is not applies on kernel space threads.
>>
>> Shirley.
>>
>>
>>
>> On Wed, Jan 30, 2019 at 8:57 AM Rami Rosen <ramirose@gmail.com> wrote:
>>
>>> Hi Shirley,
>>> >Running java based applications on the same server with a dpdk based
>>> application has an impact on the dpdk performance.
>>> Probably since the JVM generates kernel based processes. I
>>>
>>> This is true, but as far as I know, using isolcpus should prevent these
>>> processes to run on the isolated cores.
>>>
>>> Just to be on the safe side: did you make sure with cat /proc/cmdline on
>>> the kernel you are actually running indeed
>>> has the "isolcpus=1-5" you added in grub ? sometimes, especially in
>>> multi OS hosts, adding entries in /etc/default/grub and running grub2-mkconfig
>>> is not enough, if you boot from a different partition.
>>>
>>> Regards,
>>> Rami Rosen
>>>
>>>
>>>
>
> --
> regards,
> Rami Rosen
>