[dpdk-dev] [PATCH 5/8] event/dsw: avoid migration waves in large systems

[Jerin Jacob Kollanukkaran]

> -----Original Message-----
> From: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
> Sent: Monday, March 9, 2020 12:21 PM
> To: Jerin Jacob Kollanukkaran <jerinj at marvell.com>
> Cc: dev at dpdk.org; stefan.sundkvist at ericsson.com; Ola.Liljedahl at arm.com;
> Mattias Rönnblom <mattias.ronnblom at ericsson.com>
> Subject:  [PATCH 5/8] event/dsw: avoid migration waves in large systems
> 
> ----------------------------------------------------------------------
> DSW limits the rate of migrations on a per-port basis. Hence, as the number of
> cores grows, so does the total migration capacity.
> 
> In high core-count systems, this allows for a situation where flows are migrated
> to a lightly loaded port which recently already received a number of new flows
> (from other ports). The processing load generated by these new flows may not
> yet be reflected in the lightly loaded port's load estimate. The result is that the
> previously lightly loaded port is now overloaded.
> 
> This patch adds a rough estimate of the size of the inbound migrations to a
> particular port, which can be factored into the migration logic, avoiding the
> above problem.
> 
> Signed-off-by: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
> ---
> @@ -491,6 +502,9 @@ dsw_select_emigration_target(struct dsw_evdev *dsw,
>  	target_qfs[*targets_len] = *candidate_qf;
>  	(*targets_len)++;
> 
> +	rte_atomic32_add(&dsw->ports[candidate_port_id].immigration_load,
> +			 candidate_flow_load);

These are the full barriers in arm64 and PowerPC. 
Request to change the C11 mem model[1] with Load and acquire semantics
For better performance enhancement on non x86 machines.

drivers/event/opdl is already moved to C11 mem model.

[1]
https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html


> +
>  	return true;