diff mbox series

[net-next,v4,1/6] tsnep: Replace modulo operation with mask

Message ID 20230421194656.48063-2-gerhard@engleder-embedded.com (mailing list archive)
State Accepted
Commit 42fb2962b4a6f8b46aa1c141748319e01d0c7c39
Delegated to: Netdev Maintainers
Headers show
Series tsnep: XDP socket zero-copy support | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 8 this patch: 8
netdev/cc_maintainers success CCed 7 of 7 maintainers
netdev/build_clang success Errors and warnings before: 8 this patch: 8
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 8 this patch: 8
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 109 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Gerhard Engleder April 21, 2023, 7:46 p.m. UTC 
TX/RX ring size is static and power of 2 to enable compiler to optimize
modulo operation to mask operation. Make this optimization already in
the code and don't rely on the compiler.

CPU utilisation during high packet rate has not changed. So no
performance improvement has been measured. But it is best practice to
prevent modulo operations.

Suggested-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
---
 drivers/net/ethernet/engleder/tsnep.h      |  1 +
 drivers/net/ethernet/engleder/tsnep_main.c | 28 +++++++++++-----------
 2 files changed, 15 insertions(+), 14 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/engleder/tsnep.h b/drivers/net/ethernet/engleder/tsnep.h
index 058c2bcf31a7..1de26aec78d3 100644
--- a/drivers/net/ethernet/engleder/tsnep.h
+++ b/drivers/net/ethernet/engleder/tsnep.h
@@ -18,6 +18,7 @@ 
 #define TSNEP "tsnep"
 
 #define TSNEP_RING_SIZE 256
+#define TSNEP_RING_MASK (TSNEP_RING_SIZE - 1)
 #define TSNEP_RING_RX_REFILL 16
 #define TSNEP_RING_RX_REUSE (TSNEP_RING_SIZE - TSNEP_RING_SIZE / 4)
 #define TSNEP_RING_ENTRIES_PER_PAGE (PAGE_SIZE / TSNEP_DESC_SIZE)
diff --git a/drivers/net/ethernet/engleder/tsnep_main.c b/drivers/net/ethernet/engleder/tsnep_main.c
index ed1b6102cfeb..3d15e673894a 100644
--- a/drivers/net/ethernet/engleder/tsnep_main.c
+++ b/drivers/net/ethernet/engleder/tsnep_main.c
@@ -292,7 +292,7 @@  static int tsnep_tx_ring_init(struct tsnep_tx *tx)
 	}
 	for (i = 0; i < TSNEP_RING_SIZE; i++) {
 		entry = &tx->entry[i];
-		next_entry = &tx->entry[(i + 1) % TSNEP_RING_SIZE];
+		next_entry = &tx->entry[(i + 1) & TSNEP_RING_MASK];
 		entry->desc->next = __cpu_to_le64(next_entry->desc_dma);
 	}
 
@@ -381,7 +381,7 @@  static int tsnep_tx_map(struct sk_buff *skb, struct tsnep_tx *tx, int count)
 	int i;
 
 	for (i = 0; i < count; i++) {
-		entry = &tx->entry[(tx->write + i) % TSNEP_RING_SIZE];
+		entry = &tx->entry[(tx->write + i) & TSNEP_RING_MASK];
 
 		if (!i) {
 			len = skb_headlen(skb);
@@ -419,7 +419,7 @@  static int tsnep_tx_unmap(struct tsnep_tx *tx, int index, int count)
 	int i;
 
 	for (i = 0; i < count; i++) {
-		entry = &tx->entry[(index + i) % TSNEP_RING_SIZE];
+		entry = &tx->entry[(index + i) & TSNEP_RING_MASK];
 
 		if (entry->len) {
 			if (entry->type & TSNEP_TX_TYPE_SKB)
@@ -481,9 +481,9 @@  static netdev_tx_t tsnep_xmit_frame_ring(struct sk_buff *skb,
 		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
 
 	for (i = 0; i < count; i++)
-		tsnep_tx_activate(tx, (tx->write + i) % TSNEP_RING_SIZE, length,
+		tsnep_tx_activate(tx, (tx->write + i) & TSNEP_RING_MASK, length,
 				  i == count - 1);
-	tx->write = (tx->write + count) % TSNEP_RING_SIZE;
+	tx->write = (tx->write + count) & TSNEP_RING_MASK;
 
 	skb_tx_timestamp(skb);
 
@@ -516,7 +516,7 @@  static int tsnep_xdp_tx_map(struct xdp_frame *xdpf, struct tsnep_tx *tx,
 	frag = NULL;
 	len = xdpf->len;
 	for (i = 0; i < count; i++) {
-		entry = &tx->entry[(tx->write + i) % TSNEP_RING_SIZE];
+		entry = &tx->entry[(tx->write + i) & TSNEP_RING_MASK];
 		if (type & TSNEP_TX_TYPE_XDP_NDO) {
 			data = unlikely(frag) ? skb_frag_address(frag) :
 						xdpf->data;
@@ -589,9 +589,9 @@  static bool tsnep_xdp_xmit_frame_ring(struct xdp_frame *xdpf,
 	length = retval;
 
 	for (i = 0; i < count; i++)
-		tsnep_tx_activate(tx, (tx->write + i) % TSNEP_RING_SIZE, length,
+		tsnep_tx_activate(tx, (tx->write + i) & TSNEP_RING_MASK, length,
 				  i == count - 1);
-	tx->write = (tx->write + count) % TSNEP_RING_SIZE;
+	tx->write = (tx->write + count) & TSNEP_RING_MASK;
 
 	/* descriptor properties shall be valid before hardware is notified */
 	dma_wmb();
@@ -691,7 +691,7 @@  static bool tsnep_tx_poll(struct tsnep_tx *tx, int napi_budget)
 		/* xdpf is union with skb */
 		entry->skb = NULL;
 
-		tx->read = (tx->read + count) % TSNEP_RING_SIZE;
+		tx->read = (tx->read + count) & TSNEP_RING_MASK;
 
 		tx->packets++;
 		tx->bytes += length + ETH_FCS_LEN;
@@ -839,7 +839,7 @@  static int tsnep_rx_ring_init(struct tsnep_rx *rx)
 
 	for (i = 0; i < TSNEP_RING_SIZE; i++) {
 		entry = &rx->entry[i];
-		next_entry = &rx->entry[(i + 1) % TSNEP_RING_SIZE];
+		next_entry = &rx->entry[(i + 1) & TSNEP_RING_MASK];
 		entry->desc->next = __cpu_to_le64(next_entry->desc_dma);
 	}
 
@@ -925,7 +925,7 @@  static int tsnep_rx_refill(struct tsnep_rx *rx, int count, bool reuse)
 	int retval;
 
 	for (i = 0; i < count && !alloc_failed; i++) {
-		index = (rx->write + i) % TSNEP_RING_SIZE;
+		index = (rx->write + i) & TSNEP_RING_MASK;
 
 		retval = tsnep_rx_alloc_buffer(rx, index);
 		if (unlikely(retval)) {
@@ -945,7 +945,7 @@  static int tsnep_rx_refill(struct tsnep_rx *rx, int count, bool reuse)
 	}
 
 	if (enable) {
-		rx->write = (rx->write + i) % TSNEP_RING_SIZE;
+		rx->write = (rx->write + i) & TSNEP_RING_MASK;
 
 		/* descriptor properties shall be valid before hardware is
 		 * notified
@@ -1090,7 +1090,7 @@  static int tsnep_rx_poll(struct tsnep_rx *rx, struct napi_struct *napi,
 				 * empty RX ring, thus buffer cannot be used for
 				 * RX processing
 				 */
-				rx->read = (rx->read + 1) % TSNEP_RING_SIZE;
+				rx->read = (rx->read + 1) & TSNEP_RING_MASK;
 				desc_available++;
 
 				rx->dropped++;
@@ -1117,7 +1117,7 @@  static int tsnep_rx_poll(struct tsnep_rx *rx, struct napi_struct *napi,
 		 */
 		length -= TSNEP_RX_INLINE_METADATA_SIZE;
 
-		rx->read = (rx->read + 1) % TSNEP_RING_SIZE;
+		rx->read = (rx->read + 1) & TSNEP_RING_MASK;
 		desc_available++;
 
 		if (prog) {