[dpdk-dev,v2] event/sw: perform partial burst enqueues

  Previously, the sw PMD would enqueue either all or no events, depending on
if enough inflight credits were available for the new events in the burst.
If a port is enqueueing a large burst (i.e. a multiple of the credit update
quanta), this can result in suboptimal performance, and requires an
understanding of the sw PMD implementation (in particular, its credit
scheme) to tune an application's burst size.

This affects software that enqueues large bursts of new events, such as the
ethernet event adapter which uses a 128-deep event buffer, when the input
packet rate is sufficiently high.

This change makes the sw PMD enqueue as many events as it has credits, if
there are any new events in the burst.

Signed-off-by: Gage Eads <gage.eads@intel.com>
---
v2: fix commit message bug ("sw event adapter" -> "sw PMD")

 drivers/event/sw/sw_evdev_worker.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
  

> From: Eads, Gage
> Sent: Monday, March 12, 2018 2:55 PM
> To: dev@dpdk.org
> Cc: jerin.jacob@caviumnetworks.com; Van Haaren, Harry
> <harry.van.haaren@intel.com>
> Subject: [PATCH v2] event/sw: perform partial burst enqueues
> 
> Previously, the sw PMD would enqueue either all or no events, depending on
> if enough inflight credits were available for the new events in the burst.
> If a port is enqueueing a large burst (i.e. a multiple of the credit update
> quanta), this can result in suboptimal performance, and requires an
> understanding of the sw PMD implementation (in particular, its credit
> scheme) to tune an application's burst size.
> 
> This affects software that enqueues large bursts of new events, such as the
> ethernet event adapter which uses a 128-deep event buffer, when the input
> packet rate is sufficiently high.
> 
> This change makes the sw PMD enqueue as many events as it has credits, if
> there are any new events in the burst.
> 
> Signed-off-by: Gage Eads <gage.eads@intel.com>


Agree that making forward progress by enqueuing what we have credits for
makes sense for the application.

No performance degradation here, thanks for the patch:

Acked-by: Harry van Haaren <harry.van.haaren@intel.com>
  

-----Original Message-----
> Date: Tue, 13 Mar 2018 14:08:20 +0000
> From: "Van Haaren, Harry" <harry.van.haaren@intel.com>
> To: "Eads, Gage" <gage.eads@intel.com>, "dev@dpdk.org" <dev@dpdk.org>
> CC: "jerin.jacob@caviumnetworks.com" <jerin.jacob@caviumnetworks.com>
> Subject: RE: [PATCH v2] event/sw: perform partial burst enqueues
> 
> > From: Eads, Gage
> > Sent: Monday, March 12, 2018 2:55 PM
> > To: dev@dpdk.org
> > Cc: jerin.jacob@caviumnetworks.com; Van Haaren, Harry
> > <harry.van.haaren@intel.com>
> > Subject: [PATCH v2] event/sw: perform partial burst enqueues
> > 
> > Previously, the sw PMD would enqueue either all or no events, depending on
> > if enough inflight credits were available for the new events in the burst.
> > If a port is enqueueing a large burst (i.e. a multiple of the credit update
> > quanta), this can result in suboptimal performance, and requires an
> > understanding of the sw PMD implementation (in particular, its credit
> > scheme) to tune an application's burst size.
> > 
> > This affects software that enqueues large bursts of new events, such as the
> > ethernet event adapter which uses a 128-deep event buffer, when the input
> > packet rate is sufficiently high.
> > 
> > This change makes the sw PMD enqueue as many events as it has credits, if
> > there are any new events in the burst.
> > 
> > Signed-off-by: Gage Eads <gage.eads@intel.com>
> 
> 
> Agree that making forward progress by enqueuing what we have credits for
> makes sense for the application.
> 
> No performance degradation here, thanks for the patch:
> 
> Acked-by: Harry van Haaren <harry.van.haaren@intel.com>

Applied to dpdk-next-eventdev/master. Thanks.