On 14-Feb-19 9:53 AM, David Marchand wrote:
On Thu, Feb 14, 2019 at 10:39 AM Burakov, Anatoly
<anatoly.bura...@intel.com <mailto:anatoly.bura...@intel.com>> wrote:
On 13-Feb-19 4:13 PM, David Marchand wrote:
> Spawning the ctrl threads on anything that is not part of the eal
> coremask is not that polite to the rest of the system.
>
> Rather than introduce yet another eal options for this, let's take
> the startup cpu affinity as a reference and remove the eal coremask
> from it.
> If no cpu is left, then we default to the master core.
>
> The cpuset is computed once at init before the original cpu affinity.
>
> Fixes: d651ee4919cd ("eal: set affinity for control threads")
> Signed-off-by: David Marchand <david.march...@redhat.com
<mailto:david.march...@redhat.com>>
> ---
Hi David,
Maybe i didn't have enough coffee today and i'm missing something here,
but how is this different? Removing the coremask cores from the cpuset
will effectively "spawn the ctrl threads on anything that is not
part of
the EAL coremask" (which is "not that polite to the rest of the
system"), unless the application was run with taskset.
Is "taskset" the key point here? I.e. by default, we're still "not
polite", unless the user asks nicely? :)
Eheh, sorry, yes.
A bit more context then, if you want to clearly pin cpu resources for
the processes on your system (let's say having virtual machines and a
popular vswitch), I can only think of two solutions.
Either you have something to configure your processes to have them call
sched_setaffinity/pthread_set_affinity_np, or you use taskset to get
them "jailed" without them caring.
Before the incriminated commit, we were keeping all threads on the
coremask that had been passed, but as Olivier said, we would end up with
ctrl threads spanwed on core running dataplane threads as well.
Now, the ctrl threads can be spawned anywhere on all & ~coremask, with
no way to configure this.
I considered adding a new eal option, but I think relying on the current
cpu affinity is a better default behavior and I can't see drawbacks at
the moment.
--
David Marchand
OK, that makes sense. However, i feel this behavior (both old and new,
for that matter) should be better documented somewhere in the EAL docs.
--
Thanks,
Anatoly
