[PATCH net-next v9 8/9] iavf: pack iavf_ring more efficiently

From: Alexander Lobakin
Date: Thu Apr 04 2024 - 11:50:12 EST


Before replacing the Rx buffer management with libie, clean up
&iavf_ring a bit.
There are several fields not used anywhere in the code -- simply remove
them. Move ::tail up to remove a hole. Replace ::arm_wb boolean with
1-bit flag in ::flags to free 1 more byte. Finally, move ::prev_pkt_ctr
out of &iavf_tx_queue_stats -- it doesn't belong there (used for Tx
stall detection). Place it next to the stats on the ring itself to fill
the 4-byte slot.
The result: no holes and all the hot fields fit into the first 64-byte
cacheline.

Signed-off-by: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx>
---
drivers/net/ethernet/intel/iavf/iavf_txrx.h | 22 +++------------------
drivers/net/ethernet/intel/iavf/iavf_txrx.c | 12 +++++------
2 files changed, 9 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ethernet/intel/iavf/iavf_txrx.h b/drivers/net/ethernet/intel/iavf/iavf_txrx.h
index e01777531635..ed559fa6f214 100644
--- a/drivers/net/ethernet/intel/iavf/iavf_txrx.h
+++ b/drivers/net/ethernet/intel/iavf/iavf_txrx.h
@@ -227,7 +227,6 @@ struct iavf_tx_queue_stats {
u64 tx_done_old;
u64 tx_linearize;
u64 tx_force_wb;
- int prev_pkt_ctr;
u64 tx_lost_interrupt;
};

@@ -237,12 +236,6 @@ struct iavf_rx_queue_stats {
u64 alloc_buff_failed;
};

-enum iavf_ring_state_t {
- __IAVF_TX_FDIR_INIT_DONE,
- __IAVF_TX_XPS_INIT_DONE,
- __IAVF_RING_STATE_NBITS /* must be last */
-};
-
/* some useful defines for virtchannel interface, which
* is the only remaining user of header split
*/
@@ -264,10 +257,8 @@ struct iavf_ring {
struct iavf_tx_buffer *tx_bi;
struct iavf_rx_buffer *rx_bi;
};
- DECLARE_BITMAP(state, __IAVF_RING_STATE_NBITS);
- u16 queue_index; /* Queue number of ring */
- u8 dcb_tc; /* Traffic class of ring */
u8 __iomem *tail;
+ u16 queue_index; /* Queue number of ring */

/* high bit set means dynamic, use accessors routines to read/write.
* hardware only supports 2us resolution for the ITR registers.
@@ -277,22 +268,14 @@ struct iavf_ring {
u16 itr_setting;

u16 count; /* Number of descriptors */
- u16 reg_idx; /* HW register index of the ring */

/* used in interrupt processing */
u16 next_to_use;
u16 next_to_clean;

- u8 atr_sample_rate;
- u8 atr_count;
-
- bool ring_active; /* is ring online or not */
- bool arm_wb; /* do something to arm write back */
- u8 packet_stride;
-
u16 flags;
#define IAVF_TXR_FLAGS_WB_ON_ITR BIT(0)
-/* BIT(1) is free, was IAVF_RXR_FLAGS_BUILD_SKB_ENABLED */
+#define IAVF_TXR_FLAGS_ARM_WB BIT(1)
/* BIT(2) is free */
#define IAVF_TXRX_FLAGS_VLAN_TAG_LOC_L2TAG1 BIT(3)
#define IAVF_TXR_FLAGS_VLAN_TAG_LOC_L2TAG2 BIT(4)
@@ -306,6 +289,7 @@ struct iavf_ring {
struct iavf_rx_queue_stats rx_stats;
};

+ int prev_pkt_ctr; /* For Tx stall detection */
unsigned int size; /* length of descriptor ring in bytes */
dma_addr_t dma; /* physical address of ring */

diff --git a/drivers/net/ethernet/intel/iavf/iavf_txrx.c b/drivers/net/ethernet/intel/iavf/iavf_txrx.c
index a14f7f211150..1a27fa613f6d 100644
--- a/drivers/net/ethernet/intel/iavf/iavf_txrx.c
+++ b/drivers/net/ethernet/intel/iavf/iavf_txrx.c
@@ -185,7 +185,7 @@ void iavf_detect_recover_hung(struct iavf_vsi *vsi)
* pending work.
*/
packets = tx_ring->stats.packets & INT_MAX;
- if (tx_ring->tx_stats.prev_pkt_ctr == packets) {
+ if (tx_ring->prev_pkt_ctr == packets) {
iavf_force_wb(vsi, tx_ring->q_vector);
continue;
}
@@ -194,7 +194,7 @@ void iavf_detect_recover_hung(struct iavf_vsi *vsi)
* to iavf_get_tx_pending()
*/
smp_rmb();
- tx_ring->tx_stats.prev_pkt_ctr =
+ tx_ring->prev_pkt_ctr =
iavf_get_tx_pending(tx_ring, true) ? packets : -1;
}
}
@@ -320,7 +320,7 @@ static bool iavf_clean_tx_irq(struct iavf_vsi *vsi,
((j / WB_STRIDE) == 0) && (j > 0) &&
!test_bit(__IAVF_VSI_DOWN, vsi->state) &&
(IAVF_DESC_UNUSED(tx_ring) != tx_ring->count))
- tx_ring->arm_wb = true;
+ tx_ring->flags |= IAVF_TXR_FLAGS_ARM_WB;
}

/* notify netdev of completed buffers */
@@ -675,7 +675,7 @@ int iavf_setup_tx_descriptors(struct iavf_ring *tx_ring)

tx_ring->next_to_use = 0;
tx_ring->next_to_clean = 0;
- tx_ring->tx_stats.prev_pkt_ctr = -1;
+ tx_ring->prev_pkt_ctr = -1;
return 0;

err:
@@ -1491,8 +1491,8 @@ int iavf_napi_poll(struct napi_struct *napi, int budget)
clean_complete = false;
continue;
}
- arm_wb |= ring->arm_wb;
- ring->arm_wb = false;
+ arm_wb |= !!(ring->flags & IAVF_TXR_FLAGS_ARM_WB);
+ ring->flags &= ~IAVF_TXR_FLAGS_ARM_WB;
}

/* Handle case where we are called by netpoll with a budget of 0 */
--
2.44.0