[dpdk-users] Lcore impact

Shawn Lewis smlsr at tencara.com
Thu Apr 14 19:06:11 CEST 2016

You have to work with IRQBalancer as well


Is just an example document which discuss this (not so much DPDK
related)...  But the OS will attempt to balance the interrupts when you
actually want to remove or pin them down...

On Thu, Apr 14, 2016 at 1:02 PM, Alexander Kiselev <kiselev99 at gmail.com>

> 14 апр. 2016 г., в 19:35, Shawn Lewis <smlsr at tencara.com> написал(а):
> Lots of things...
> One just because you have a process running on an lcore, does not mean
> thats all that runs on it.  Unless you have told the kernel at boot to NOT
> use those specific cores, those cores will be used for many things OS
> related.
> Generally yes, but unless I start sending data to socket there is no
> packet loss.  I did about 10 test runs in a raw and everythis was ok. And
> there is no other application running on that test machine that uses cpu
> cores.
> So the question is why this socket operations influence the other lcore?
> IRQBlance
> System OS operations.
> Other Applications.
> So by doing file i/o you are generating interrupts, where those interrupts
> get serviced is up to IRQBalancer.  So could be any one of your cores.
> That is a good point. I can use cpu affinity feature to bind unterruption
> handler to the core not used in my test. But I send data locally over
> localhost. Is it possible to use cpu affinity in that case?
> On Thu, Apr 14, 2016 at 12:31 PM, Alexander Kiselev <kiselev99 at gmail.com>
> wrote:
>> Could someone give me any hints about what could cause permormance issues
>> in a situation where one lcore doing a lot of linux system calls
>> (read/write on socket) slow down the other lcore doing packet forwarding?
>> In my test the forwarding lcore doesn't share any memory structures with
>> the other lcore that sends test data to socket. Both lcores pins to
>> different processors cores. So therotically they shouldn't have any impact
>> on each other but they do, once one lcore starts sending data to socket the
>> other lcore starts dropping packets. Why?

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