sfc: The size of the RX recycle ring should be more flexible

Ideally the size would depend on the link speed, but the recycle
ring is created when the interface is brought up before the driver
knows the link speed. So size it for the maximum speed of a given NIC.
PowerPC is only supported on SFN7xxx and SFN8xxx NICs.

With this patch on a 40G NIC the number of calls to alloc_pages and
friends went down from about 18% to under 2%.
On a 10G NIC the number of calls to alloc_pages and friends went down
from about 15% to 0 (perf did not capture any calls during the 60
second test).
On a 100G NIC the number of calls to alloc_pages and friends went down
from about 23% to 4%.

Reported-by: Íñigo Huguet <ihuguet@redhat.com>
Signed-off-by: Martin Habets <habetsm.xilinx@gmail.com>
Link: https://lore.kernel.org/r/20220131111054.cp4f6foyinaarwbn@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/sfc/ef10.c

@@ -3990,6 +3990,30 @@ static unsigned int ef10_check_caps(const struct efx_nic *efx,
 	}
 }
 
+static unsigned int efx_ef10_recycle_ring_size(const struct efx_nic *efx)
+{
+	unsigned int ret = EFX_RECYCLE_RING_SIZE_10G;
+
+	/* There is no difference between PFs and VFs. The side is based on
+	 * the maximum link speed of a given NIC.
+	 */
+	switch (efx->pci_dev->device & 0xfff) {
+	case 0x0903:	/* Farmingdale can do up to 10G */
+		break;
+	case 0x0923:	/* Greenport can do up to 40G */
+	case 0x0a03:	/* Medford can do up to 40G */
+		ret *= 4;
+		break;
+	default:	/* Medford2 can do up to 100G */
+		ret *= 10;
+	}
+
+	if (IS_ENABLED(CONFIG_PPC64))
+		ret *= 4;
+
+	return ret;
+}
+
 #define EF10_OFFLOAD_FEATURES		\
 	(NETIF_F_IP_CSUM |		\
 	 NETIF_F_HW_VLAN_CTAG_FILTER |	\
@@ -4106,6 +4130,7 @@ const struct efx_nic_type efx_hunt_a0_vf_nic_type = {
 	.check_caps = ef10_check_caps,
 	.print_additional_fwver = efx_ef10_print_additional_fwver,
 	.sensor_event = efx_mcdi_sensor_event,
+	.rx_recycle_ring_size = efx_ef10_recycle_ring_size,
 };
 
 const struct efx_nic_type efx_hunt_a0_nic_type = {
@@ -4243,4 +4268,5 @@ const struct efx_nic_type efx_hunt_a0_nic_type = {
 	.check_caps = ef10_check_caps,
 	.print_additional_fwver = efx_ef10_print_additional_fwver,
 	.sensor_event = efx_mcdi_sensor_event,
+	.rx_recycle_ring_size = efx_ef10_recycle_ring_size,
 };

drivers/net/ethernet/sfc/ef100_nic.c

@@ -23,6 +23,7 @@
 #include "ef100_rx.h"
 #include "ef100_tx.h"
 #include "ef100_netdev.h"
+#include "rx_common.h"
 
 #define EF100_MAX_VIS 4096
 #define EF100_NUM_MCDI_BUFFERS	1
@@ -696,6 +697,12 @@ static unsigned int ef100_check_caps(const struct efx_nic *efx,
 	}
 }
 
+static unsigned int efx_ef100_recycle_ring_size(const struct efx_nic *efx)
+{
+	/* Maximum link speed for Riverhead is 100G */
+	return 10 * EFX_RECYCLE_RING_SIZE_10G;
+}
+
 /*	NIC level access functions
  */
 #define EF100_OFFLOAD_FEATURES	(NETIF_F_HW_CSUM | NETIF_F_RXCSUM |	\
@@ -770,6 +777,7 @@ const struct efx_nic_type ef100_pf_nic_type = {
 	.rx_push_rss_context_config = efx_mcdi_rx_push_rss_context_config,
 	.rx_pull_rss_context_config = efx_mcdi_rx_pull_rss_context_config,
 	.rx_restore_rss_contexts = efx_mcdi_rx_restore_rss_contexts,
+	.rx_recycle_ring_size = efx_ef100_recycle_ring_size,
 
 	.reconfigure_mac = ef100_reconfigure_mac,
 	.reconfigure_port = efx_mcdi_port_reconfigure,
@@ -849,6 +857,7 @@ const struct efx_nic_type ef100_vf_nic_type = {
 	.rx_pull_rss_config = efx_mcdi_rx_pull_rss_config,
 	.rx_push_rss_config = efx_mcdi_pf_rx_push_rss_config,
 	.rx_restore_rss_contexts = efx_mcdi_rx_restore_rss_contexts,
+	.rx_recycle_ring_size = efx_ef100_recycle_ring_size,
 
 	.reconfigure_mac = ef100_reconfigure_mac,
 	.test_nvram = efx_new_mcdi_nvram_test_all,

drivers/net/ethernet/sfc/net_driver.h

@@ -1282,6 +1282,7 @@ struct efx_udp_tunnel {
  * @udp_tnl_has_port: Check if a port has been added as UDP tunnel
  * @print_additional_fwver: Dump NIC-specific additional FW version info
  * @sensor_event: Handle a sensor event from MCDI
+ * @rx_recycle_ring_size: Size of the RX recycle ring
  * @revision: Hardware architecture revision
  * @txd_ptr_tbl_base: TX descriptor ring base address
  * @rxd_ptr_tbl_base: RX descriptor ring base address
@@ -1460,6 +1461,7 @@ struct efx_nic_type {
 	size_t (*print_additional_fwver)(struct efx_nic *efx, char *buf,
 					 size_t len);
 	void (*sensor_event)(struct efx_nic *efx, efx_qword_t *ev);
+	unsigned int (*rx_recycle_ring_size)(const struct efx_nic *efx);
 
 	int revision;
 	unsigned int txd_ptr_tbl_base;

drivers/net/ethernet/sfc/nic_common.h

@@ -195,6 +195,11 @@ static inline void efx_sensor_event(struct efx_nic *efx, efx_qword_t *ev)
 		efx->type->sensor_event(efx, ev);
 }
 
+static inline unsigned int efx_rx_recycle_ring_size(const struct efx_nic *efx)
+{
+	return efx->type->rx_recycle_ring_size(efx);
+}
+
 /* Some statistics are computed as A - B where A and B each increase
  * linearly with some hardware counter(s) and the counters are read
  * asynchronously.  If the counters contributing to B are always read

drivers/net/ethernet/sfc/rx_common.c

@@ -23,13 +23,6 @@ module_param(rx_refill_threshold, uint, 0444);
 MODULE_PARM_DESC(rx_refill_threshold,
 		 "RX descriptor ring refill threshold (%)");
 
-/* Number of RX buffers to recycle pages for.  When creating the RX page recycle
- * ring, this number is divided by the number of buffers per page to calculate
- * the number of pages to store in the RX page recycle ring.
- */
-#define EFX_RECYCLE_RING_SIZE_IOMMU 4096
-#define EFX_RECYCLE_RING_SIZE_NOIOMMU (2 * EFX_RX_PREFERRED_BATCH)
-
 /* RX maximum head room required.
  *
  * This must be at least 1 to prevent overflow, plus one packet-worth
@@ -141,16 +134,7 @@ static void efx_init_rx_recycle_ring(struct efx_rx_queue *rx_queue)
 	unsigned int bufs_in_recycle_ring, page_ring_size;
 	struct efx_nic *efx = rx_queue->efx;
 
-	/* Set the RX recycle ring size */
-#ifdef CONFIG_PPC64
-	bufs_in_recycle_ring = EFX_RECYCLE_RING_SIZE_IOMMU;
-#else
-	if (iommu_present(&pci_bus_type))
-		bufs_in_recycle_ring = EFX_RECYCLE_RING_SIZE_IOMMU;
-	else
-		bufs_in_recycle_ring = EFX_RECYCLE_RING_SIZE_NOIOMMU;
-#endif /* CONFIG_PPC64 */
-
+	bufs_in_recycle_ring = efx_rx_recycle_ring_size(efx);
 	page_ring_size = roundup_pow_of_two(bufs_in_recycle_ring /
 					    efx->rx_bufs_per_page);
 	rx_queue->page_ring = kcalloc(page_ring_size,

drivers/net/ethernet/sfc/rx_common.h

@@ -18,6 +18,12 @@
 #define EFX_RX_MAX_FRAGS DIV_ROUND_UP(EFX_MAX_FRAME_LEN(EFX_MAX_MTU), \
 				      EFX_RX_USR_BUF_SIZE)
 
+/* Number of RX buffers to recycle pages for.  When creating the RX page recycle
+ * ring, this number is divided by the number of buffers per page to calculate
+ * the number of pages to store in the RX page recycle ring.
+ */
+#define EFX_RECYCLE_RING_SIZE_10G	256
+
 static inline u8 *efx_rx_buf_va(struct efx_rx_buffer *buf)
 {
 	return page_address(buf->page) + buf->page_offset;

drivers/net/ethernet/sfc/siena.c

@@ -25,6 +25,7 @@
 #include "mcdi_port_common.h"
 #include "selftest.h"
 #include "siena_sriov.h"
+#include "rx_common.h"
 
 /* Hardware control for SFC9000 family including SFL9021 (aka Siena). */
 
@@ -958,6 +959,12 @@ static unsigned int siena_check_caps(const struct efx_nic *efx,
 	return 0;
 }
 
+static unsigned int efx_siena_recycle_ring_size(const struct efx_nic *efx)
+{
+	/* Maximum link speed is 10G */
+	return EFX_RECYCLE_RING_SIZE_10G;
+}
+
 /**************************************************************************
  *
  * Revision-dependent attributes used by efx.c and nic.c
@@ -1098,4 +1105,5 @@ const struct efx_nic_type siena_a0_nic_type = {
 	.rx_hash_key_size = 16,
 	.check_caps = siena_check_caps,
 	.sensor_event = efx_mcdi_sensor_event,
+	.rx_recycle_ring_size = efx_siena_recycle_ring_size,
 };