[next-queue] igb: Fix the transmission mode of queue 0 for Qav mode

Message ID 20180331000652.2855-1-vinicius.gomes@intel.com
State Under Review
Delegated to: Jeff Kirsher
Headers show
Series
  • [next-queue] igb: Fix the transmission mode of queue 0 for Qav mode
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Commit Message

Vinicius Costa Gomes March 31, 2018, 12:06 a.m.
When Qav mode is enabled, queue 0 should be kept on Stream Reservation
mode. From the i210 datasheet, section 8.12.19:

"Note: Queue0 QueueMode must be set to 1b when TransmitMode is set to
Qav." ("QueueMode 1b" represents the Stream Reservation mode)

The solution is to give queue 0 the all the credits it might need, so
it has priority over queue 1.

A situation where this can happen is when cbs is "installed" only on
queue 1, leaving queue 0 alone. For example:

$ tc qdisc replace dev enp2s0 handle 100: parent root mqprio num_tc 3 \
     	   map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 queues 1@0 1@1 2@2 hw 0

$ tc qdisc replace dev enp2s0 parent 100:2 cbs locredit -1470 \
     	   hicredit 30 sendslope -980000 idleslope 20000 offload 1

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

Comments

Brown, Aaron F April 14, 2018, 2:28 a.m. | #1
> From: netdev-owner@vger.kernel.org [mailto:netdev-
> owner@vger.kernel.org] On Behalf Of Vinicius Costa Gomes
> Sent: Friday, March 30, 2018 5:07 PM
> To: intel-wired-lan@lists.osuosl.org
> Cc: Gomes, Vinicius <vinicius.gomes@intel.com>; Kirsher, Jeffrey T
> <jeffrey.t.kirsher@intel.com>; netdev@vger.kernel.org; Sanchez-Palencia,
> Jesus <jesus.sanchez-palencia@intel.com>; Guedes, Andre
> <andre.guedes@intel.com>
> Subject: [next-queue PATCH] igb: Fix the transmission mode of queue 0 for
> Qav mode
> 
> When Qav mode is enabled, queue 0 should be kept on Stream Reservation
> mode. From the i210 datasheet, section 8.12.19:
> 
> "Note: Queue0 QueueMode must be set to 1b when TransmitMode is set to
> Qav." ("QueueMode 1b" represents the Stream Reservation mode)
> 
> The solution is to give queue 0 the all the credits it might need, so
> it has priority over queue 1.
> 
> A situation where this can happen is when cbs is "installed" only on
> queue 1, leaving queue 0 alone. For example:
> 
> $ tc qdisc replace dev enp2s0 handle 100: parent root mqprio num_tc 3 \
>      	   map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 queues 1@0 1@1 2@2 hw 0
> 
> $ tc qdisc replace dev enp2s0 parent 100:2 cbs locredit -1470 \
>      	   hicredit 30 sendslope -980000 idleslope 20000 offload 1
> 
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 

Tested by: Aaron Brown <aaron.f.brown@intel.com>
Brown, Aaron F April 17, 2018, 12:55 a.m. | #2
> From: Brown, Aaron F
> Sent: Friday, April 13, 2018 7:28 PM
> To: 'Vinicius Costa Gomes' <vinicius.gomes@intel.com>; intel-wired-
> lan@lists.osuosl.org
> Cc: Gomes, Vinicius <vinicius.gomes@intel.com>; Kirsher, Jeffrey T
> <jeffrey.t.kirsher@intel.com>; netdev@vger.kernel.org; Sanchez-Palencia,
> Jesus <jesus.sanchez-palencia@intel.com>; Guedes, Andre
> <andre.guedes@intel.com>
> Subject: RE: [next-queue PATCH] igb: Fix the transmission mode of queue 0
> for Qav mode
> 
> > From: netdev-owner@vger.kernel.org [mailto:netdev-
> > owner@vger.kernel.org] On Behalf Of Vinicius Costa Gomes
> > Sent: Friday, March 30, 2018 5:07 PM
> > To: intel-wired-lan@lists.osuosl.org
> > Cc: Gomes, Vinicius <vinicius.gomes@intel.com>; Kirsher, Jeffrey T
> > <jeffrey.t.kirsher@intel.com>; netdev@vger.kernel.org; Sanchez-Palencia,
> > Jesus <jesus.sanchez-palencia@intel.com>; Guedes, Andre
> > <andre.guedes@intel.com>
> > Subject: [next-queue PATCH] igb: Fix the transmission mode of queue 0 for
> > Qav mode
> >
> > When Qav mode is enabled, queue 0 should be kept on Stream
> Reservation
> > mode. From the i210 datasheet, section 8.12.19:
> >
> > "Note: Queue0 QueueMode must be set to 1b when TransmitMode is set
> to
> > Qav." ("QueueMode 1b" represents the Stream Reservation mode)
> >
> > The solution is to give queue 0 the all the credits it might need, so
> > it has priority over queue 1.
> >
> > A situation where this can happen is when cbs is "installed" only on
> > queue 1, leaving queue 0 alone. For example:
> >
> > $ tc qdisc replace dev enp2s0 handle 100: parent root mqprio num_tc 3 \
> >      	   map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 queues 1@0 1@1 2@2 hw 0
> >
> > $ tc qdisc replace dev enp2s0 parent 100:2 cbs locredit -1470 \
> >      	   hicredit 30 sendslope -980000 idleslope 20000 offload 1
> >
> > Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
> > ---
> >  drivers/net/ethernet/intel/igb/igb_main.c | 17 ++++++++++++++++-
> >  1 file changed, 16 insertions(+), 1 deletion(-)
> >
> 
> Tested by: Aaron Brown <aaron.f.brown@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>

Patch

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index c1c0bc30a16d..cce7ada89255 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -1700,7 +1700,22 @@  static void igb_configure_cbs(struct igb_adapter *adapter, int queue,
 	WARN_ON(hw->mac.type != e1000_i210);
 	WARN_ON(queue < 0 || queue > 1);
 
-	if (enable) {
+	if (enable || queue == 0) {
+		/* i210 does not allow the queue 0 to be in the Strict
+		 * Priority mode while the Qav mode is enabled, so,
+		 * instead of disabling strict priority mode, we give
+		 * queue 0 the maximum of credits possible.
+		 *
+		 * See section 8.12.19 of the i210 datasheet, "Note:
+		 * Queue0 QueueMode must be set to 1b when
+		 * TransmitMode is set to Qav."
+		 */
+		if (queue == 0 && !enable) {
+			/* max "linkspeed" idleslope in kbps */
+			idleslope = 1000000;
+			hicredit = ETH_FRAME_LEN;
+		}
+
 		set_tx_desc_fetch_prio(hw, queue, TX_QUEUE_PRIO_HIGH);
 		set_queue_mode(hw, queue, QUEUE_MODE_STREAM_RESERVATION);