Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 99f5711e authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

mlx4: do not use rwlock in fast path 



Using a reader-writer lock in fast path is silly, when we can
instead use RCU or a seqlock.

For mlx4 hwstamp clock, a seqlock is the way to go, removing
two atomic operations and false sharing.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Reviewed-by: default avatarTariq Toukan <tariqt@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d5bc1613

drivers/net/ethernet/mellanox/mlx4/en_clock.c

+18 −17
Original line number Diff line number Diff line
@@ -62,12 +62,13 @@ void mlx4_en_fill_hwtstamps(struct mlx4_en_dev *mdev, 
			    struct skb_shared_hwtstamps *hwts,

			    u64 timestamp)

{

	unsigned long flags;

	unsigned int seq;

	u64 nsec;



	read_lock_irqsave(&mdev->clock_lock, flags);

	do {

		seq = read_seqbegin(&mdev->clock_lock);

		nsec = timecounter_cyc2time(&mdev->clock, timestamp);

	read_unlock_irqrestore(&mdev->clock_lock, flags);

	} while (read_seqretry(&mdev->clock_lock, seq));



	memset(hwts, 0, sizeof(struct skb_shared_hwtstamps));

	hwts->hwtstamp = ns_to_ktime(nsec);
@@ -95,9 +96,9 @@ void mlx4_en_ptp_overflow_check(struct mlx4_en_dev *mdev) 
	unsigned long flags;



	if (timeout) {

		write_lock_irqsave(&mdev->clock_lock, flags);

		write_seqlock_irqsave(&mdev->clock_lock, flags);

		timecounter_read(&mdev->clock);

		write_unlock_irqrestore(&mdev->clock_lock, flags);

		write_sequnlock_irqrestore(&mdev->clock_lock, flags);

		mdev->last_overflow_check = jiffies;

	}

}
@@ -128,10 +129,10 @@ static int mlx4_en_phc_adjfreq(struct ptp_clock_info *ptp, s32 delta) 
	adj *= delta;

	diff = div_u64(adj, 1000000000ULL);



	write_lock_irqsave(&mdev->clock_lock, flags);

	write_seqlock_irqsave(&mdev->clock_lock, flags);

	timecounter_read(&mdev->clock);

	mdev->cycles.mult = neg_adj ? mult - diff : mult + diff;

	write_unlock_irqrestore(&mdev->clock_lock, flags);

	write_sequnlock_irqrestore(&mdev->clock_lock, flags);



	return 0;

}
@@ -149,9 +150,9 @@ static int mlx4_en_phc_adjtime(struct ptp_clock_info *ptp, s64 delta) 
						ptp_clock_info);

	unsigned long flags;



	write_lock_irqsave(&mdev->clock_lock, flags);

	write_seqlock_irqsave(&mdev->clock_lock, flags);

	timecounter_adjtime(&mdev->clock, delta);

	write_unlock_irqrestore(&mdev->clock_lock, flags);

	write_sequnlock_irqrestore(&mdev->clock_lock, flags);



	return 0;

}
@@ -172,9 +173,9 @@ static int mlx4_en_phc_gettime(struct ptp_clock_info *ptp, 
	unsigned long flags;

	u64 ns;



	write_lock_irqsave(&mdev->clock_lock, flags);

	write_seqlock_irqsave(&mdev->clock_lock, flags);

	ns = timecounter_read(&mdev->clock);

	write_unlock_irqrestore(&mdev->clock_lock, flags);

	write_sequnlock_irqrestore(&mdev->clock_lock, flags);



	*ts = ns_to_timespec64(ns);
@@ -198,9 +199,9 @@ static int mlx4_en_phc_settime(struct ptp_clock_info *ptp, 
	unsigned long flags;



	/* reset the timecounter */

	write_lock_irqsave(&mdev->clock_lock, flags);

	write_seqlock_irqsave(&mdev->clock_lock, flags);

	timecounter_init(&mdev->clock, &mdev->cycles, ns);

	write_unlock_irqrestore(&mdev->clock_lock, flags);

	write_sequnlock_irqrestore(&mdev->clock_lock, flags);



	return 0;

}
@@ -266,7 +267,7 @@ void mlx4_en_init_timestamp(struct mlx4_en_dev *mdev) 
	if (mdev->ptp_clock)

		return;



	rwlock_init(&mdev->clock_lock);

	seqlock_init(&mdev->clock_lock);



	memset(&mdev->cycles, 0, sizeof(mdev->cycles));

	mdev->cycles.read = mlx4_en_read_clock;
@@ -276,10 +277,10 @@ void mlx4_en_init_timestamp(struct mlx4_en_dev *mdev) 
		clocksource_khz2mult(1000 * dev->caps.hca_core_clock, mdev->cycles.shift);

	mdev->nominal_c_mult = mdev->cycles.mult;



	write_lock_irqsave(&mdev->clock_lock, flags);

	write_seqlock_irqsave(&mdev->clock_lock, flags);

	timecounter_init(&mdev->clock, &mdev->cycles,

			 ktime_to_ns(ktime_get_real()));

	write_unlock_irqrestore(&mdev->clock_lock, flags);

	write_sequnlock_irqrestore(&mdev->clock_lock, flags);



	/* Calculate period in seconds to call the overflow watchdog - to make

	 * sure counter is checked at least once every wrap around.

drivers/net/ethernet/mellanox/mlx4/mlx4_en.h

+1 −1
Original line number Diff line number Diff line
@@ -424,9 +424,9 @@ struct mlx4_en_dev { 
	u32                     priv_pdn;

	spinlock_t              uar_lock;

	u8			mac_removed[MLX4_MAX_PORTS + 1];

	rwlock_t		clock_lock;

	u32			nominal_c_mult;

	struct cyclecounter	cycles;

	seqlock_t		clock_lock;

	struct timecounter	clock;

	unsigned long		last_overflow_check;

	unsigned long		overflow_period;