| Message ID | 20141113192746.12579.91054.stgit@ahduyck-server |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
On Thu, 2014-11-13 at 11:27 -0800, Alexander Duyck wrote: > This change makes it so that load_acquire is used when reading the Rx > descriptor. The advantage of load_acquire is that it allows for a > much > lower cost barrier on x86, ia64, powerpc, arm64, and s390 > architectures > than a traditional memory barrier when dealing with reads that only > have > to synchronize to system 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: Jeff Kirsher <jeffrey.t.kirsher@intel.com> > Cc: Matthew Vick <matthew.vick@intel.com> > Cc: Don Skidmore <donald.c.skidmore@intel.com> > Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com> > --- > drivers/net/ethernet/intel/fm10k/fm10k_main.c | 8 +++----- > drivers/net/ethernet/intel/igb/igb_main.c | 8 +++----- > drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 11 ++++------- > 3 files changed, 10 insertions(+), 17 deletions(-) Based on the discussion on patch 01 of the series, it appears changes are coming to the series, so I won't be picking up this patch. I will wait for Alex to re-spin the series with the suggested changes.
diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_main.c b/drivers/net/ethernet/intel/fm10k/fm10k_main.c index e645af4..2d4923c 100644 --- a/drivers/net/ethernet/intel/fm10k/fm10k_main.c +++ b/drivers/net/ethernet/intel/fm10k/fm10k_main.c @@ -620,14 +620,12 @@ 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)) - 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(); + if (!load_acquire(&rx_desc->d.staterr)) + break; /* 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 a2d72a8..a55cd54 100644 --- a/drivers/net/ethernet/intel/igb/igb_main.c +++ b/drivers/net/ethernet/intel/igb/igb_main.c @@ -6918,14 +6918,12 @@ 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)) - 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(); + if (!load_acquire(&rx_desc->wb.upper.status_error)) + break; /* 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 d2df4e3..007f174 100644 --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c @@ -2003,15 +2003,12 @@ 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)) - 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(); + if (!load_acquire(&rx_desc->wb.upper.status_error)) + break; /* retrieve a buffer from the ring */ skb = ixgbe_fetch_rx_buffer(rx_ring, rx_desc);
This change makes it so that load_acquire is used when reading the Rx descriptor. The advantage of load_acquire is that it allows for a much lower cost barrier on x86, ia64, powerpc, arm64, and s390 architectures than a traditional memory barrier when dealing with reads that only have to synchronize to system 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: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Cc: Matthew Vick <matthew.vick@intel.com> Cc: Don Skidmore <donald.c.skidmore@intel.com> Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com> --- drivers/net/ethernet/intel/fm10k/fm10k_main.c | 8 +++----- drivers/net/ethernet/intel/igb/igb_main.c | 8 +++----- drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 11 ++++------- 3 files changed, 10 insertions(+), 17 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html