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Date: Thu, 30 Jul 2015 15:19:28 -0700
From: Alexander Duyck <alexander.h.duyck@...hat.com>
To: netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org
Cc: jeffrey.t.kirsher@...el.com
Subject: [PATCH] ixgbe: Limit lowest interrupt rate for adaptive interrupt
moderation to 12K
This patch updates the lowest limit for adaptive interrupt interrupt
moderation to roughly 12K interrupts per second.
The way I came about reaching 12K as the desired interrupt rate is by
testing with UDP flows. Specifically I had a simple test that ran a
netperf UDP_STREAM test at varying sizes. What I found was as the packet
sizes increased the performance fell steadily behind until we were only
able to receive at ~4Gb/s with a message size of 65507. A bit of digging
found that we were dropping packets for the socket in the network stack,
and looking at things further what I found was I could solve it by increasing
the interrupt rate, or increasing the rmem_default/rmem_max. What I found was
that when the interrupt coalescing resulted in more data being processed
per interrupt than could be stored in the socket buffer we started losing
packets and the performance dropped. So I reached 12K based on the
following math.
rmem_default = 212992
skb->truesize = 2994
212992 / 2994 = 71.14 packets to fill the buffer
packet rate at 1514 packet size is 812744pps
71.14 / 812744 = 87.9us to fill socket buffer
>>From there it was just a matter of choosing the interrupt rate and
providing a bit of wiggle room which is why I decided to go with 12K
interrupts per second as that uses a value of 84us.
The data below is based on VM to VM over a direct assigned ixgbe interface.
The test run was:
netperf -H <ip> -t UDP_STREAM"
Socket Message Elapsed Messages CPU Service
Size Size Time Okay Errors Throughput Util Demand
bytes bytes secs # # 10^6bits/sec % SS us/KB
Before:
212992 65507 60.00 1100662 0 9613.4 10.89 0.557
212992 60.00 473474 4135.4 11.27 0.576
After:
212992 65507 60.00 1100413 0 9611.2 10.73 0.549
212992 60.00 974132 8508.3 11.69 0.598
Using bare metal the data is similar but not as dramatic as the throughput
increases from about 8.5Gb/s to 9.5Gb/s.
Signed-off-by: Alexander Duyck <alexander.h.duyck@...hat.com>
---
drivers/net/ethernet/intel/ixgbe/ixgbe.h | 3 +--
drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c | 2 +-
drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c | 2 +-
drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 4 ++--
4 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
index ac3ac2a20386..93ebb30e6cbd 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
@@ -539,8 +539,7 @@ struct hwmon_buff {
#define IXGBE_MIN_RSC_ITR 24
#define IXGBE_100K_ITR 40
#define IXGBE_20K_ITR 200
-#define IXGBE_10K_ITR 400
-#define IXGBE_8K_ITR 500
+#define IXGBE_12K_ITR 336
/* ixgbe_test_staterr - tests bits in Rx descriptor status and error fields */
static inline __le32 ixgbe_test_staterr(union ixgbe_adv_rx_desc *rx_desc,
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
index f7aeb560a504..6a929cf2ce7c 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
@@ -2279,7 +2279,7 @@ static int ixgbe_set_coalesce(struct net_device *netdev,
adapter->tx_itr_setting = ec->tx_coalesce_usecs;
if (adapter->tx_itr_setting == 1)
- tx_itr_param = IXGBE_10K_ITR;
+ tx_itr_param = IXGBE_12K_ITR;
else
tx_itr_param = adapter->tx_itr_setting;
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
index 68e1e757ecef..f3168bcc7d87 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
@@ -866,7 +866,7 @@ static int ixgbe_alloc_q_vector(struct ixgbe_adapter *adapter,
if (txr_count && !rxr_count) {
/* tx only vector */
if (adapter->tx_itr_setting == 1)
- q_vector->itr = IXGBE_10K_ITR;
+ q_vector->itr = IXGBE_12K_ITR;
else
q_vector->itr = adapter->tx_itr_setting;
} else {
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 3e6a9319c718..d35dedbb9560 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -2252,7 +2252,7 @@ static void ixgbe_update_itr(struct ixgbe_q_vector *q_vector,
/* simple throttlerate management
* 0-10MB/s lowest (100000 ints/s)
* 10-20MB/s low (20000 ints/s)
- * 20-1249MB/s bulk (8000 ints/s)
+ * 20-1249MB/s bulk (12000 ints/s)
*/
/* what was last interrupt timeslice? */
timepassed_us = q_vector->itr >> 2;
@@ -2341,7 +2341,7 @@ static void ixgbe_set_itr(struct ixgbe_q_vector *q_vector)
new_itr = IXGBE_20K_ITR;
break;
case bulk_latency:
- new_itr = IXGBE_8K_ITR;
+ new_itr = IXGBE_12K_ITR;
break;
default:
break;
--
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