From: Shay Agroskin Date: Tue, 5 Jun 2018 06:22:18 +0000 (+0300) Subject: net/mlx5e: Replace PTP clock lock from RW lock to seq lock X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=64109f1dc41f25f4a9c6b114e04b6266bf4128ad;p=openwrt%2Fstaging%2Fblogic.git net/mlx5e: Replace PTP clock lock from RW lock to seq lock Changed "priv.clock.lock" lock from 'rw_lock' to 'seq_lock' in order to improve packet rate performance. Tested on Intel(R) Xeon(R) CPU E5-2660 v2 @ 2.20GHz. Sent 64b packets between two peers connected by ConnectX-5, and measured packet rate for the receiver in three modes: no time-stamping (base rate) time-stamping using rw_lock (old lock) for critical region time-stamping using seq_lock (new lock) for critical region Only the receiver time stamped its packets. The measured packet rate improvements are: Single flow (multiple TX rings to single RX ring): without timestamping: 4.26 (M packets)/sec with rw-lock (old lock): 4.1 (M packets)/sec with seq-lock (new lock): 4.16 (M packets)/sec 1.46% improvement Multiple flows (multiple TX rings to six RX rings): without timestamping: 22 (M packets)/sec with rw-lock (old lock): 11.7 (M packets)/sec with seq-lock (new lock): 21.3 (M packets)/sec 82.05% improvement The packet rate improvement is due to the lack of atomic operations for the 'readers' by the seq-lock. Since there are much more 'readers' than 'writers' contention on this lock, almost all atomic operations are saved. this results in a dramatic decrease in overall cache misses. Signed-off-by: Shay Agroskin Signed-off-by: Saeed Mahameed --- diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c index 3f767cde4c1d..0d90b1b4a3d3 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c @@ -111,10 +111,10 @@ static void mlx5_pps_out(struct work_struct *work) for (i = 0; i < clock->ptp_info.n_pins; i++) { u64 tstart; - write_lock_irqsave(&clock->lock, flags); + write_seqlock_irqsave(&clock->lock, flags); tstart = clock->pps_info.start[i]; clock->pps_info.start[i] = 0; - write_unlock_irqrestore(&clock->lock, flags); + write_sequnlock_irqrestore(&clock->lock, flags); if (!tstart) continue; @@ -132,10 +132,10 @@ static void mlx5_timestamp_overflow(struct work_struct *work) overflow_work); unsigned long flags; - write_lock_irqsave(&clock->lock, flags); + write_seqlock_irqsave(&clock->lock, flags); timecounter_read(&clock->tc); mlx5_update_clock_info_page(clock->mdev); - write_unlock_irqrestore(&clock->lock, flags); + write_sequnlock_irqrestore(&clock->lock, flags); schedule_delayed_work(&clock->overflow_work, clock->overflow_period); } @@ -147,10 +147,10 @@ static int mlx5_ptp_settime(struct ptp_clock_info *ptp, u64 ns = timespec64_to_ns(ts); unsigned long flags; - write_lock_irqsave(&clock->lock, flags); + write_seqlock_irqsave(&clock->lock, flags); timecounter_init(&clock->tc, &clock->cycles, ns); mlx5_update_clock_info_page(clock->mdev); - write_unlock_irqrestore(&clock->lock, flags); + write_sequnlock_irqrestore(&clock->lock, flags); return 0; } @@ -162,9 +162,9 @@ static int mlx5_ptp_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts) u64 ns; unsigned long flags; - write_lock_irqsave(&clock->lock, flags); + write_seqlock_irqsave(&clock->lock, flags); ns = timecounter_read(&clock->tc); - write_unlock_irqrestore(&clock->lock, flags); + write_sequnlock_irqrestore(&clock->lock, flags); *ts = ns_to_timespec64(ns); @@ -177,10 +177,10 @@ static int mlx5_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta) ptp_info); unsigned long flags; - write_lock_irqsave(&clock->lock, flags); + write_seqlock_irqsave(&clock->lock, flags); timecounter_adjtime(&clock->tc, delta); mlx5_update_clock_info_page(clock->mdev); - write_unlock_irqrestore(&clock->lock, flags); + write_sequnlock_irqrestore(&clock->lock, flags); return 0; } @@ -203,12 +203,12 @@ static int mlx5_ptp_adjfreq(struct ptp_clock_info *ptp, s32 delta) adj *= delta; diff = div_u64(adj, 1000000000ULL); - write_lock_irqsave(&clock->lock, flags); + write_seqlock_irqsave(&clock->lock, flags); timecounter_read(&clock->tc); clock->cycles.mult = neg_adj ? clock->nominal_c_mult - diff : clock->nominal_c_mult + diff; mlx5_update_clock_info_page(clock->mdev); - write_unlock_irqrestore(&clock->lock, flags); + write_sequnlock_irqrestore(&clock->lock, flags); return 0; } @@ -307,12 +307,12 @@ static int mlx5_perout_configure(struct ptp_clock_info *ptp, ts.tv_nsec = rq->perout.start.nsec; ns = timespec64_to_ns(&ts); cycles_now = mlx5_read_internal_timer(mdev); - write_lock_irqsave(&clock->lock, flags); + write_seqlock_irqsave(&clock->lock, flags); nsec_now = timecounter_cyc2time(&clock->tc, cycles_now); nsec_delta = ns - nsec_now; cycles_delta = div64_u64(nsec_delta << clock->cycles.shift, clock->cycles.mult); - write_unlock_irqrestore(&clock->lock, flags); + write_sequnlock_irqrestore(&clock->lock, flags); time_stamp = cycles_now + cycles_delta; field_select = MLX5_MTPPS_FS_PIN_MODE | MLX5_MTPPS_FS_PATTERN | @@ -471,14 +471,14 @@ void mlx5_pps_event(struct mlx5_core_dev *mdev, ts.tv_sec += 1; ts.tv_nsec = 0; ns = timespec64_to_ns(&ts); - write_lock_irqsave(&clock->lock, flags); + write_seqlock_irqsave(&clock->lock, flags); nsec_now = timecounter_cyc2time(&clock->tc, cycles_now); nsec_delta = ns - nsec_now; cycles_delta = div64_u64(nsec_delta << clock->cycles.shift, clock->cycles.mult); clock->pps_info.start[pin] = cycles_now + cycles_delta; schedule_work(&clock->pps_info.out_work); - write_unlock_irqrestore(&clock->lock, flags); + write_sequnlock_irqrestore(&clock->lock, flags); break; default: mlx5_core_err(mdev, " Unhandled event\n"); @@ -498,7 +498,7 @@ void mlx5_init_clock(struct mlx5_core_dev *mdev) mlx5_core_warn(mdev, "invalid device_frequency_khz, aborting HW clock init\n"); return; } - rwlock_init(&clock->lock); + seqlock_init(&clock->lock); clock->cycles.read = read_internal_timer; clock->cycles.shift = MLX5_CYCLES_SHIFT; clock->cycles.mult = clocksource_khz2mult(dev_freq, diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.h b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.h index 02e2e4575e4f..263cb6e2aeee 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.h +++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.h @@ -46,11 +46,13 @@ static inline int mlx5_clock_get_ptp_index(struct mlx5_core_dev *mdev) static inline ktime_t mlx5_timecounter_cyc2time(struct mlx5_clock *clock, u64 timestamp) { + unsigned int seq; u64 nsec; - read_lock(&clock->lock); - nsec = timecounter_cyc2time(&clock->tc, timestamp); - read_unlock(&clock->lock); + do { + seq = read_seqbegin(&clock->lock); + nsec = timecounter_cyc2time(&clock->tc, timestamp); + } while (read_seqretry(&clock->lock, seq)); return ns_to_ktime(nsec); } diff --git a/include/linux/mlx5/driver.h b/include/linux/mlx5/driver.h index 2a0c845f6bdb..b7fce2c9443d 100644 --- a/include/linux/mlx5/driver.h +++ b/include/linux/mlx5/driver.h @@ -805,7 +805,7 @@ struct mlx5_pps { }; struct mlx5_clock { - rwlock_t lock; + seqlock_t lock; struct cyclecounter cycles; struct timecounter tc; struct hwtstamp_config hwtstamp_config;