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Date: Tue, 25 Nov 2014 12:35:53 -0800 From: Alexander Duyck <alexander.h.duyck@...hat.com> To: linux-arch@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Cc: mathieu.desnoyers@...ymtl.ca, peterz@...radead.org, benh@...nel.crashing.org, heiko.carstens@...ibm.com, mingo@...nel.org, mikey@...ling.org, linux@....linux.org.uk, donald.c.skidmore@...el.com, matthew.vick@...el.com, geert@...ux-m68k.org, jeffrey.t.kirsher@...el.com, romieu@...zoreil.com, paulmck@...ux.vnet.ibm.com, nic_swsd@...ltek.com, arnd@...db.de, will.deacon@....com, michael@...erman.id.au, tony.luck@...el.com, torvalds@...ux-foundation.org, oleg@...hat.com, schwidefsky@...ibm.com, fweisbec@...il.com, davem@...emloft.net Subject: [PATCH v7 4/4] fm10k/igb/ixgbe: Use dma_rmb on Rx descriptor reads This change makes it so that dma_rmb is used when reading the Rx descriptor. The advantage of dma_rmb is that it allows for a much lower cost barrier on x86, powerpc, arm, and arm64 architectures than a traditional memory barrier when dealing with reads that only have to synchronize to coherent memory. In addition I have updated the code so that it just checks to see if any bits have been set instead of just the DD bit since the DD bit will always be set as a part of a descriptor write-back so we just need to check for a non-zero value being present at that memory location rather than just checking for any specific bit. This allows the code itself to appear much cleaner and allows the compiler more room to optimize. Cc: Matthew Vick <matthew.vick@...el.com> Cc: Don Skidmore <donald.c.skidmore@...el.com> Acked-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com> Signed-off-by: Alexander Duyck <alexander.h.duyck@...hat.com> --- drivers/net/ethernet/intel/fm10k/fm10k_main.c | 6 +++--- drivers/net/ethernet/intel/igb/igb_main.c | 6 +++--- drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 9 ++++----- 3 files changed, 10 insertions(+), 11 deletions(-) diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_main.c b/drivers/net/ethernet/intel/fm10k/fm10k_main.c index 73457ed..b348178 100644 --- a/drivers/net/ethernet/intel/fm10k/fm10k_main.c +++ b/drivers/net/ethernet/intel/fm10k/fm10k_main.c @@ -620,14 +620,14 @@ static bool fm10k_clean_rx_irq(struct fm10k_q_vector *q_vector, rx_desc = FM10K_RX_DESC(rx_ring, rx_ring->next_to_clean); - if (!fm10k_test_staterr(rx_desc, FM10K_RXD_STATUS_DD)) + if (!rx_desc->d.staterr) break; /* This memory barrier is needed to keep us from reading * any other fields out of the rx_desc until we know the - * RXD_STATUS_DD bit is set + * descriptor has been written back */ - rmb(); + dma_rmb(); /* retrieve a buffer from the ring */ skb = fm10k_fetch_rx_buffer(rx_ring, rx_desc, skb); diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c index 3c02216..ecf38cf 100644 --- a/drivers/net/ethernet/intel/igb/igb_main.c +++ b/drivers/net/ethernet/intel/igb/igb_main.c @@ -6922,14 +6922,14 @@ static bool igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget) rx_desc = IGB_RX_DESC(rx_ring, rx_ring->next_to_clean); - if (!igb_test_staterr(rx_desc, E1000_RXD_STAT_DD)) + if (!rx_desc->wb.upper.status_error) break; /* This memory barrier is needed to keep us from reading * any other fields out of the rx_desc until we know the - * RXD_STAT_DD bit is set + * descriptor has been written back */ - rmb(); + dma_rmb(); /* retrieve a buffer from the ring */ skb = igb_fetch_rx_buffer(rx_ring, rx_desc, skb); diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c index c19af9f..5bc9650 100644 --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c @@ -2006,15 +2006,14 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector, rx_desc = IXGBE_RX_DESC(rx_ring, rx_ring->next_to_clean); - if (!ixgbe_test_staterr(rx_desc, IXGBE_RXD_STAT_DD)) + if (!rx_desc->wb.upper.status_error) break; - /* - * This memory barrier is needed to keep us from reading + /* This memory barrier is needed to keep us from reading * any other fields out of the rx_desc until we know the - * RXD_STAT_DD bit is set + * descriptor has been written back */ - rmb(); + dma_rmb(); /* retrieve a buffer from the ring */ skb = ixgbe_fetch_rx_buffer(rx_ring, rx_desc); -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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