Re: core performance

[amit sehas <cun23@yahoo.com>]

Thanks for the responses, this is on AWS, which is utilizing Xeon with hyperthreading. Not utilizing hyperthreading is not an option.

After trying a few things i am narrowing down on the following approach:

only for the critical threads we could utilize:  rte_thread_set_priority to RTE_THREAD_PRIORITY_REALTIME_CRITICAL

however this API requires a rte_thread_t parameter, if we utilize rte_eal_remote_launch, we are not provided with this parameter.
I am searching through the code to see if there is an API where i can obtain the rte_thread_t for the current thread that was launched with rte_eal_remote_launch.

regards






On Monday, September 23, 2024 at 03:18:11 PM PDT, Nishant Verma <vnish11@gmail.com> wrote: 





Also make sure all core you are using are physical core not the logical core. 
Secondly, check your core isolation options and apply them accordingly.


.

Regards,
Nishant Verma


On Mon, Sep 23, 2024 at 6:04 PM Wisam Jaddo <wisamm@nvidia.com> wrote:
> Hello Amit,
> 
>> -----Original Message-----
>> From: amit sehas <cun23@yahoo.com>
>> Sent: Monday, September 23, 2024 11:57 PM
>> To: users@dpdk.org
>> Subject: core performance
>> 
>> We are seeing different dpdk threads (launched via rte_eal_remote_launch()),
>> demonstrate very different performance.
>> 
>> 
>> 
>> After placing counters all over the code, we realize that some threads are
>> uniformly slow, in other words there is no application level issue that is
>> throttling one thread over the other. We come to the conculsion that either
>> the Cores on which they are running are not at the same frequency which
>> seems doubtful or the threads are not getting a chance to execute on the cores
>> uniformly.
>> 
>> 
>> 
>> It seems that isolcpus has been deprecated in recent versions of linux.
>> 
>> 
>> 
>> What is the recommended approach to prevent the kernel from utilizing some
>> CPU threads, for anything other than the threads that are launched on them.
> 
> If you are wishing to run each thread on separate core, try to use rte_eal_mp_remote_launch()
> instead of rte_eal_remote_launch(), make sure that your CPU is isolated, and you are passing correct
> Cores that were isolated to your app using -c, -l.
> 
> 
>> 
>> 
>> 
>> Is there some API in dpdk which also helps us determine which CPU core the
>> thread is pinned to?
>> 
>> I did not find any code in dpdk which actually performed pinning of a thread to
>> a CPU core.
>> 
>> 
>> 
>> In our case it is more or less certain that the different threads are simply not
>> getting the same CPU core time, as a result some are demonstrating higher
>> throughput than the others ...
>> 
>> 
>> 
>> how do we fix this?
> 
> BRs,
> Wisam Jaddo
>