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Date: Wed, 13 Mar 2024 13:54:56 +0100
From: Ivan Vecera <ivecera@...hat.com>
To: netdev@...r.kernel.org
Cc: pawel.chmielewski@...el.com,
aleksandr.loktionov@...el.com,
mschmidt@...hat.com,
Hugo Ferreira <hferreir@...hat.com>,
Jesse Brandeburg <jesse.brandeburg@...el.com>,
Tony Nguyen <anthony.l.nguyen@...el.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
intel-wired-lan@...ts.osuosl.org (moderated list:INTEL ETHERNET DRIVERS),
linux-kernel@...r.kernel.org (open list)
Subject: [PATCH net] i40e: Enforce software interrupt during busy-poll exit
As for ice bug fixed by commit b7306b42beaf ("ice: manage interrupts
during poll exit") I'm seeing the similar issue also with i40e driver.
In certain situation when busy-loop is enabled together with adaptive
coalescing, the driver occasionally miss that there are outstanding
descriptors to clean when exiting busy poll.
Try to catch the remaining work by triggering a software interrupt
when exiting busy poll. No extra interrupts will be generated when
busy polling is not used.
The issue was found when running sockperf ping-pong tcp test with
adaptive coalescing and busy poll enabled (50 as value busy_pool
and busy_read sysctl knobs) and results in huge latency spikes
with more than 100000us.
The fix is inspired from the ice driver and do the following:
1) During napi poll exit in case of busy-poll (napo_complete_done()
returns false) this is recorded to q_vector that we were in busy
loop.
2) In i40e_update_enable_itr()
- updates refreshed ITR intervals directly using PFINT_ITRN register
- if we are exiting ordinary poll then just enables the interrupt
using PFINT_DYN_CTLN
- if we are exiting busy poll then enables the interrupt and
additionally triggers an immediate software interrupt to catch any
pending clean-ups
3) Reuses unused 3rd ITR (interrupt throttle) index and set it to
20K interrupts per second to limit the number of these sw interrupts.
Test results
============
Prior:
[root@...l-per640-07 net]# sockperf ping-pong -i 10.9.9.1 --tcp -m 1000 --mps=max -t 120
sockperf: == version #3.10-no.git ==
sockperf[CLIENT] send on:sockperf: using recvfrom() to block on socket(s)
[ 0] IP = 10.9.9.1 PORT = 11111 # TCP
sockperf: Warmup stage (sending a few dummy messages)...
sockperf: Starting test...
sockperf: Test end (interrupted by timer)
sockperf: Test ended
sockperf: [Total Run] RunTime=119.999 sec; Warm up time=400 msec; SentMessages=2438563; ReceivedMessages=2438562
sockperf: ========= Printing statistics for Server No: 0
sockperf: [Valid Duration] RunTime=119.549 sec; SentMessages=2429473; ReceivedMessages=2429473
sockperf: ====> avg-latency=24.571 (std-dev=93.297, mean-ad=4.904, median-ad=1.510, siqr=1.063, cv=3.797, std-error=0.060, 99.0% ci=[24.417, 24.725])
sockperf: # dropped messages = 0; # duplicated messages = 0; # out-of-order messages = 0
sockperf: Summary: Latency is 24.571 usec
sockperf: Total 2429473 observations; each percentile contains 24294.73 observations
sockperf: ---> <MAX> observation = 103294.331
sockperf: ---> percentile 99.999 = 45.633
sockperf: ---> percentile 99.990 = 37.013
sockperf: ---> percentile 99.900 = 35.910
sockperf: ---> percentile 99.000 = 33.390
sockperf: ---> percentile 90.000 = 28.626
sockperf: ---> percentile 75.000 = 27.741
sockperf: ---> percentile 50.000 = 26.743
sockperf: ---> percentile 25.000 = 25.614
sockperf: ---> <MIN> observation = 12.220
After:
[root@...l-per640-07 net]# sockperf ping-pong -i 10.9.9.1 --tcp -m 1000 --mps=max -t 120
sockperf: == version #3.10-no.git ==
sockperf[CLIENT] send on:sockperf: using recvfrom() to block on socket(s)
[ 0] IP = 10.9.9.1 PORT = 11111 # TCP
sockperf: Warmup stage (sending a few dummy messages)...
sockperf: Starting test...
sockperf: Test end (interrupted by timer)
sockperf: Test ended
sockperf: [Total Run] RunTime=119.999 sec; Warm up time=400 msec; SentMessages=2400055; ReceivedMessages=2400054
sockperf: ========= Printing statistics for Server No: 0
sockperf: [Valid Duration] RunTime=119.549 sec; SentMessages=2391186; ReceivedMessages=2391186
sockperf: ====> avg-latency=24.965 (std-dev=5.934, mean-ad=4.642, median-ad=1.485, siqr=1.067, cv=0.238, std-error=0.004, 99.0% ci=[24.955, 24.975])
sockperf: # dropped messages = 0; # duplicated messages = 0; # out-of-order messages = 0
sockperf: Summary: Latency is 24.965 usec
sockperf: Total 2391186 observations; each percentile contains 23911.86 observations
sockperf: ---> <MAX> observation = 195.841
sockperf: ---> percentile 99.999 = 45.026
sockperf: ---> percentile 99.990 = 39.009
sockperf: ---> percentile 99.900 = 35.922
sockperf: ---> percentile 99.000 = 33.482
sockperf: ---> percentile 90.000 = 28.902
sockperf: ---> percentile 75.000 = 27.821
sockperf: ---> percentile 50.000 = 26.860
sockperf: ---> percentile 25.000 = 25.685
sockperf: ---> <MIN> observation = 12.277
Reported-by: Hugo Ferreira <hferreir@...hat.com>
Signed-off-by: Ivan Vecera <ivecera@...hat.com>
---
drivers/net/ethernet/intel/i40e/i40e.h | 1 +
drivers/net/ethernet/intel/i40e/i40e_main.c | 6 +++
.../net/ethernet/intel/i40e/i40e_register.h | 2 +
drivers/net/ethernet/intel/i40e/i40e_txrx.c | 46 ++++++++++++++-----
drivers/net/ethernet/intel/i40e/i40e_txrx.h | 1 +
5 files changed, 45 insertions(+), 11 deletions(-)
diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
index 9b701615c7c6..4d2b05de6c63 100644
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -908,6 +908,7 @@ struct i40e_q_vector {
struct rcu_head rcu; /* to avoid race with update stats on free */
char name[I40E_INT_NAME_STR_LEN];
bool arm_wb_state;
+ bool in_busy_poll;
int irq_num; /* IRQ assigned to this q_vector */
} ____cacheline_internodealigned_in_smp;
diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index 89a3401d20ab..1ea6d06b0acc 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -3915,6 +3915,12 @@ static void i40e_vsi_configure_msix(struct i40e_vsi *vsi)
q_vector->tx.target_itr >> 1);
q_vector->tx.current_itr = q_vector->tx.target_itr;
+ /* Set ITR for software interrupts triggered after exiting
+ * busy-loop polling.
+ */
+ wr32(hw, I40E_PFINT_ITRN(I40E_SW_ITR, vector - 1),
+ I40E_ITR_20K);
+
wr32(hw, I40E_PFINT_RATEN(vector - 1),
i40e_intrl_usec_to_reg(vsi->int_rate_limit));
diff --git a/drivers/net/ethernet/intel/i40e/i40e_register.h b/drivers/net/ethernet/intel/i40e/i40e_register.h
index 14ab642cafdb..baa6bb68bcf8 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_register.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_register.h
@@ -335,6 +335,8 @@
#define I40E_PFINT_DYN_CTLN_INTERVAL_SHIFT 5
#define I40E_PFINT_DYN_CTLN_SW_ITR_INDX_ENA_SHIFT 24
#define I40E_PFINT_DYN_CTLN_SW_ITR_INDX_ENA_MASK I40E_MASK(0x1, I40E_PFINT_DYN_CTLN_SW_ITR_INDX_ENA_SHIFT)
+#define I40E_PFINT_DYN_CTLN_SW_ITR_INDX_SHIFT 25
+#define I40E_PFINT_DYN_CTLN_SW_ITR_INDX_MASK I40E_MASK(0x3, I40E_PFINT_DYN_CTLN_SW_ITR_INDX_SHIFT)
#define I40E_PFINT_ICR0 0x00038780 /* Reset: CORER */
#define I40E_PFINT_ICR0_INTEVENT_SHIFT 0
#define I40E_PFINT_ICR0_INTEVENT_MASK I40E_MASK(0x1, I40E_PFINT_ICR0_INTEVENT_SHIFT)
diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 0d7177083708..356c3140adf3 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -2658,8 +2658,22 @@ static inline u32 i40e_buildreg_itr(const int type, u16 itr)
return val;
}
-/* a small macro to shorten up some long lines */
-#define INTREG I40E_PFINT_DYN_CTLN
+static inline u32 i40e_buildreg_swint(int type)
+{
+ u32 val;
+
+ /* 1. Enable the interrupt
+ * 2. Do not modify any ITR interval
+ * 3. Trigger a SW interrupt specified by type
+ */
+ val = I40E_PFINT_DYN_CTLN_INTENA_MASK |
+ I40E_PFINT_DYN_CTLN_ITR_INDX_MASK | /* set noitr */
+ I40E_PFINT_DYN_CTLN_SWINT_TRIG_MASK |
+ I40E_PFINT_DYN_CTLN_SW_ITR_INDX_ENA_MASK |
+ FIELD_PREP(I40E_PFINT_DYN_CTLN_SW_ITR_INDX_MASK, type);
+
+ return val;
+}
/* The act of updating the ITR will cause it to immediately trigger. In order
* to prevent this from throwing off adaptive update statistics we defer the
@@ -2702,8 +2716,8 @@ static inline void i40e_update_enable_itr(struct i40e_vsi *vsi,
*/
if (q_vector->rx.target_itr < q_vector->rx.current_itr) {
/* Rx ITR needs to be reduced, this is highest priority */
- intval = i40e_buildreg_itr(I40E_RX_ITR,
- q_vector->rx.target_itr);
+ wr32(hw, I40E_PFINT_ITRN(I40E_RX_ITR, q_vector->reg_idx),
+ q_vector->rx.target_itr >> 1);
q_vector->rx.current_itr = q_vector->rx.target_itr;
q_vector->itr_countdown = ITR_COUNTDOWN_START;
} else if ((q_vector->tx.target_itr < q_vector->tx.current_itr) ||
@@ -2712,25 +2726,33 @@ static inline void i40e_update_enable_itr(struct i40e_vsi *vsi,
/* Tx ITR needs to be reduced, this is second priority
* Tx ITR needs to be increased more than Rx, fourth priority
*/
- intval = i40e_buildreg_itr(I40E_TX_ITR,
- q_vector->tx.target_itr);
+ wr32(hw, I40E_PFINT_ITRN(I40E_TX_ITR, q_vector->reg_idx),
+ q_vector->tx.target_itr >> 1);
q_vector->tx.current_itr = q_vector->tx.target_itr;
q_vector->itr_countdown = ITR_COUNTDOWN_START;
} else if (q_vector->rx.current_itr != q_vector->rx.target_itr) {
/* Rx ITR needs to be increased, third priority */
- intval = i40e_buildreg_itr(I40E_RX_ITR,
- q_vector->rx.target_itr);
+ wr32(hw, I40E_PFINT_ITRN(I40E_RX_ITR, q_vector->reg_idx),
+ q_vector->rx.target_itr >> 1);
q_vector->rx.current_itr = q_vector->rx.target_itr;
q_vector->itr_countdown = ITR_COUNTDOWN_START;
} else {
/* No ITR update, lowest priority */
- intval = i40e_buildreg_itr(I40E_ITR_NONE, 0);
if (q_vector->itr_countdown)
q_vector->itr_countdown--;
}
- if (!test_bit(__I40E_VSI_DOWN, vsi->state))
- wr32(hw, INTREG(q_vector->reg_idx), intval);
+ /* Do not enable interrupt if VSI is down */
+ if (test_bit(__I40E_VSI_DOWN, vsi->state))
+ return;
+
+ if (!q_vector->in_busy_poll) {
+ intval = i40e_buildreg_itr(I40E_ITR_NONE, 0);
+ } else {
+ q_vector->in_busy_poll = false;
+ intval = i40e_buildreg_swint(I40E_SW_ITR);
+ }
+ wr32(hw, I40E_PFINT_DYN_CTLN(q_vector->reg_idx), intval);
}
/**
@@ -2845,6 +2867,8 @@ int i40e_napi_poll(struct napi_struct *napi, int budget)
*/
if (likely(napi_complete_done(napi, work_done)))
i40e_update_enable_itr(vsi, q_vector);
+ else
+ q_vector->in_busy_poll = true;
return min(work_done, budget - 1);
}
diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.h b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
index abf15067eb5d..2cdc7de6301c 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
@@ -68,6 +68,7 @@ enum i40e_dyn_idx {
/* these are indexes into ITRN registers */
#define I40E_RX_ITR I40E_IDX_ITR0
#define I40E_TX_ITR I40E_IDX_ITR1
+#define I40E_SW_ITR I40E_IDX_ITR2
/* Supported RSS offloads */
#define I40E_DEFAULT_RSS_HENA ( \
--
2.43.0
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