| Message ID | 20240315092042.145669-1-ivecera@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v3] i40e: Enforce software interrupt during busy-poll exit | expand |
On Fri, Mar 15, 2024 at 10:20 AM Ivan Vecera <ivecera@redhat.com> wrote: > As for ice bug fixed by commit b7306b42beaf ("ice: manage interrupts > during poll exit") followed by commit 23be7075b318 ("ice: fix software > generating extra interrupts") 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 misses 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) Extends i40e_buildreg_itr() to be able to add an enforced software > interrupt into built value > 2) In i40e_update_enable_itr() enforces a software interrupt trigger > if we are exiting busy poll 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@dell-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@dell-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 Those are the numbers from the original measurements, but I confirmed with Ivan that he re-tested with v3 and the overall picture was the same. > Fixes: 0bcd952feec7 ("ethernet/intel: consolidate NAPI and NAPI exit") > Reported-by: Hugo Ferreira <hferreir@redhat.com> > Reviewed-by: Michal Schmidt <mschmidt@redhat.com> Yeah. > Signed-off-by: Ivan Vecera <ivecera@redhat.com> > --- > Changes since v2 > - eliminated two writes in hot-path (thx Jesse) I like this improvement. Michal
On 3/15/2024 2:20 AM, Ivan Vecera wrote: ... > -static inline u32 i40e_buildreg_itr(const int type, u16 itr) > +/** > + * i40e_buildreg_itr - build a value for writing to I40E_PFINT_DYN_CTLN register > + * @itr_idx - interrupt throttling index > + * @interval - interrupt throttling interval value in usecs > + * @force_swint - force software interrupt nit: kdoc doesn't like this style New warnings added 1a2,4 > drivers/net/ethernet/intel/i40e/i40e_txrx.c:2650: warning: Function parameter or struct member 'itr_idx' not described in 'i40e_buildreg_itr' > drivers/net/ethernet/intel/i40e/i40e_txrx.c:2650: warning: Function parameter or struct member 'interval' not described in 'i40e_buildreg_itr' > drivers/net/ethernet/intel/i40e/i40e_txrx.c:2650: warning: Function parameter or struct member 'force_swint' not described in 'i40e_buildreg_itr' Per-file breakdown Thanks, Tony > + * > + * The function builds a value for I40E_PFINT_DYN_CTLN register that > + * is used to update interrupt throttling interval for specified ITR index > + * and optionally enforces a software interrupt. If the @itr_idx is equal > + * to I40E_ITR_NONE then no interval change is applied and only @force_swint > + * parameter is taken into account. If the interval change and enforced > + * software interrupt are not requested then the built value just enables > + * appropriate vector interrupt. > + **/ > +static u32 i40e_buildreg_itr(enum i40e_dyn_idx itr_idx, u16 interval, > + bool force_swint) > { > u32 val; >
diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h index ba24f3fa92c3..2fbabcdb5bb5 100644 --- a/drivers/net/ethernet/intel/i40e/i40e.h +++ b/drivers/net/ethernet/intel/i40e/i40e.h @@ -955,6 +955,7 @@ 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 f86578857e8a..6576a0081093 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_main.c +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c @@ -3911,6 +3911,12 @@ 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..432afbb64201 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_register.h +++ b/drivers/net/ethernet/intel/i40e/i40e_register.h @@ -333,8 +333,11 @@ #define I40E_PFINT_DYN_CTLN_ITR_INDX_SHIFT 3 #define I40E_PFINT_DYN_CTLN_ITR_INDX_MASK I40E_MASK(0x3, I40E_PFINT_DYN_CTLN_ITR_INDX_SHIFT) #define I40E_PFINT_DYN_CTLN_INTERVAL_SHIFT 5 +#define I40E_PFINT_DYN_CTLN_INTERVAL_MASK I40E_MASK(0xFFF, I40E_PFINT_DYN_CTLN_INTERVAL_SHIFT) #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..2438fc4fbada 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c @@ -2630,7 +2630,22 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget, return failure ? budget : (int)total_rx_packets; } -static inline u32 i40e_buildreg_itr(const int type, u16 itr) +/** + * i40e_buildreg_itr - build a value for writing to I40E_PFINT_DYN_CTLN register + * @itr_idx - interrupt throttling index + * @interval - interrupt throttling interval value in usecs + * @force_swint - force software interrupt + * + * The function builds a value for I40E_PFINT_DYN_CTLN register that + * is used to update interrupt throttling interval for specified ITR index + * and optionally enforces a software interrupt. If the @itr_idx is equal + * to I40E_ITR_NONE then no interval change is applied and only @force_swint + * parameter is taken into account. If the interval change and enforced + * software interrupt are not requested then the built value just enables + * appropriate vector interrupt. + **/ +static u32 i40e_buildreg_itr(enum i40e_dyn_idx itr_idx, u16 interval, + bool force_swint) { u32 val; @@ -2644,23 +2659,33 @@ static inline u32 i40e_buildreg_itr(const int type, u16 itr) * an event in the PBA anyway so we need to rely on the automask * to hold pending events for us until the interrupt is re-enabled * - * The itr value is reported in microseconds, and the register - * value is recorded in 2 microsecond units. For this reason we - * only need to shift by the interval shift - 1 instead of the - * full value. + * We have to shift the given value as it is reported in microseconds + * and the register value is recorded in 2 microsecond units. */ - itr &= I40E_ITR_MASK; + interval >>= 1; + /* 1. Enable vector interrupt + * 2. Update the interval for the specified ITR index + * (I40E_ITR_NONE in the register is used to indicate that + * no interval update is requested) + */ val = I40E_PFINT_DYN_CTLN_INTENA_MASK | - (type << I40E_PFINT_DYN_CTLN_ITR_INDX_SHIFT) | - (itr << (I40E_PFINT_DYN_CTLN_INTERVAL_SHIFT - 1)); + FIELD_PREP(I40E_PFINT_DYN_CTLN_ITR_INDX_MASK, itr_idx) | + FIELD_PREP(I40E_PFINT_DYN_CTLN_INTERVAL_MASK, interval); + + /* 3. Enforce software interrupt trigger if requested + * (These software interrupts rate is limited by ITR2 that is + * set to 20K interrupts per second) + */ + if (force_swint) + val |= 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, + I40E_SW_ITR); return val; } -/* a small macro to shorten up some long lines */ -#define INTREG I40E_PFINT_DYN_CTLN - /* 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 * update so that it can only happen so often. So after either Tx or Rx are @@ -2680,7 +2705,9 @@ static inline void i40e_update_enable_itr(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector) { struct i40e_hw *hw = &vsi->back->hw; - u32 intval; + int itr_idx = I40E_ITR_NONE; + u16 interval = 0; + u32 itr_val; /* If we don't have MSIX, then we only need to re-enable icr0 */ if (!test_bit(I40E_FLAG_MSIX_ENA, vsi->back->flags)) { @@ -2702,8 +2729,8 @@ 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); + itr_idx = I40E_RX_ITR; + interval = q_vector->rx.target_itr; 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 +2739,36 @@ 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); + itr_idx = I40E_TX_ITR; + interval = q_vector->tx.target_itr; 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); + itr_idx = I40E_RX_ITR; + interval = q_vector->rx.target_itr; 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 update interrupt control register if VSI is down */ + if (test_bit(__I40E_VSI_DOWN, vsi->state)) + return; + + /* Update ITR interval if necessary and enforce software interrupt + * if we are exiting busy poll. + */ + if (q_vector->in_busy_poll) { + itr_val = i40e_buildreg_itr(itr_idx, interval, true); + q_vector->in_busy_poll = false; + } else { + itr_val = i40e_buildreg_itr(itr_idx, interval, false); + } + wr32(hw, I40E_PFINT_DYN_CTLN(q_vector->reg_idx), itr_val); } /** @@ -2845,6 +2883,8 @@ 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 ( \
As for ice bug fixed by commit b7306b42beaf ("ice: manage interrupts during poll exit") followed by commit 23be7075b318 ("ice: fix software generating extra interrupts") 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 misses 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) Extends i40e_buildreg_itr() to be able to add an enforced software interrupt into built value 2) In i40e_update_enable_itr() enforces a software interrupt trigger if we are exiting busy poll 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@dell-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@dell-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 Fixes: 0bcd952feec7 ("ethernet/intel: consolidate NAPI and NAPI exit") Reported-by: Hugo Ferreira <hferreir@redhat.com> Reviewed-by: Michal Schmidt <mschmidt@redhat.com> Signed-off-by: Ivan Vecera <ivecera@redhat.com> --- Changes since v2 - eliminated two writes in hot-path (thx Jesse) Changes since v1 - added Fixes: tag drivers/net/ethernet/intel/i40e/i40e.h | 1 + drivers/net/ethernet/intel/i40e/i40e_main.c | 6 ++ .../net/ethernet/intel/i40e/i40e_register.h | 3 + drivers/net/ethernet/intel/i40e/i40e_txrx.c | 82 ++++++++++++++----- drivers/net/ethernet/intel/i40e/i40e_txrx.h | 1 + 5 files changed, 72 insertions(+), 21 deletions(-)