hv_netvsc: use reciprocal divide to speed up percent calculation

Every packet sent checks the available ring space. The calculation
can be sped up by using reciprocal divide which is multiplication.

Since ring_size can only be configured by module parameter, so it doesn't
have to be passed around everywhere. Also it should be unsigned
since it is number of pages.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index 7226230561de713d3230e784d046f045f89ec6f4..3d940c67ea94e6e126703425e73e132cae65b906 100644 (file)
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -146,7 +146,6 @@ struct hv_netvsc_packet {
 
 struct netvsc_device_info {
        unsigned char mac_adr[ETH_ALEN];
-       int  ring_size;
        u32  num_chn;
        u32  send_sections;
        u32  recv_sections;
@@ -188,6 +187,9 @@ struct rndis_message;
 struct netvsc_device;
 struct net_device_context;
 
+extern u32 netvsc_ring_bytes;
+extern struct reciprocal_value netvsc_ring_reciprocal;
+
 struct netvsc_device *netvsc_device_add(struct hv_device *device,
                                        const struct netvsc_device_info *info);
 int netvsc_alloc_recv_comp_ring(struct netvsc_device *net_device, u32 q_idx);
@@ -804,8 +806,6 @@ struct netvsc_device {
 
        struct rndis_device *extension;
 
-       int ring_size;
-
        u32 max_pkt; /* max number of pkt in one send, e.g. 8 */
        u32 pkt_align; /* alignment bytes, e.g. 8 */
 

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 4b931f017a253b5f137420be4cd98b7839346f9e..e4bcd202a56a25d46fde6dc458e727e948cadce1 100644 (file)
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -31,6 +31,7 @@
 #include <linux/vmalloc.h>
 #include <linux/rtnetlink.h>
 #include <linux/prefetch.h>
+#include <linux/reciprocal_div.h>
 
 #include <asm/sync_bitops.h>
 
@@ -588,14 +589,11 @@ void netvsc_device_remove(struct hv_device *device)
  * Get the percentage of available bytes to write in the ring.
  * The return value is in range from 0 to 100.
  */
-static inline u32 hv_ringbuf_avail_percent(
-               struct hv_ring_buffer_info *ring_info)
+static u32 hv_ringbuf_avail_percent(const struct hv_ring_buffer_info *ring_info)
 {
-       u32 avail_read, avail_write;
+       u32 avail_write = hv_get_bytes_to_write(ring_info);
 
-       hv_get_ringbuffer_availbytes(ring_info, &avail_read, &avail_write);
-
-       return avail_write * 100 / ring_info->ring_datasize;
+       return reciprocal_divide(avail_write  * 100, netvsc_ring_reciprocal);
 }
 
 static inline void netvsc_free_send_slot(struct netvsc_device *net_device,
@@ -1249,7 +1247,6 @@ struct netvsc_device *netvsc_device_add(struct hv_device *device,
                                const struct netvsc_device_info *device_info)
 {
        int i, ret = 0;
-       int ring_size = device_info->ring_size;
        struct netvsc_device *net_device;
        struct net_device *ndev = hv_get_drvdata(device);
        struct net_device_context *net_device_ctx = netdev_priv(ndev);
@@ -1261,8 +1258,6 @@ struct netvsc_device *netvsc_device_add(struct hv_device *device,
        for (i = 0; i < VRSS_SEND_TAB_SIZE; i++)
                net_device_ctx->tx_table[i] = 0;
 
-       net_device->ring_size = ring_size;
-
        /* Because the device uses NAPI, all the interrupt batching and
         * control is done via Net softirq, not the channel handling
         */
@@ -1289,10 +1284,9 @@ struct netvsc_device *netvsc_device_add(struct hv_device *device,
                       netvsc_poll, NAPI_POLL_WEIGHT);
 
        /* Open the channel */
-       ret = vmbus_open(device->channel, ring_size * PAGE_SIZE,
-                        ring_size * PAGE_SIZE, NULL, 0,
-                        netvsc_channel_cb,
-                        net_device->chan_table);
+       ret = vmbus_open(device->channel, netvsc_ring_bytes,
+                        netvsc_ring_bytes,  NULL, 0,
+                        netvsc_channel_cb, net_device->chan_table);
 
        if (ret != 0) {
                netif_napi_del(&net_device->chan_table[0].napi);

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 5129647d420ca2e9b91bc782f9b8920c573a5c7c..ba690e1737ab7c9662cd6c2b4dd9f39073777d42 100644 (file)
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -35,6 +35,7 @@
 #include <linux/slab.h>
 #include <linux/rtnetlink.h>
 #include <linux/netpoll.h>
+#include <linux/reciprocal_div.h>
 
 #include <net/arp.h>
 #include <net/route.h>
@@ -54,9 +55,11 @@
 #define LINKCHANGE_INT (2 * HZ)
 #define VF_TAKEOVER_INT (HZ / 10)
 
-static int ring_size = 128;
-module_param(ring_size, int, S_IRUGO);
+static unsigned int ring_size __ro_after_init = 128;
+module_param(ring_size, uint, S_IRUGO);
 MODULE_PARM_DESC(ring_size, "Ring buffer size (# of pages)");
+unsigned int netvsc_ring_bytes __ro_after_init;
+struct reciprocal_value netvsc_ring_reciprocal __ro_after_init;
 
 static const u32 default_msg = NETIF_MSG_DRV | NETIF_MSG_PROBE |
                                NETIF_MSG_LINK | NETIF_MSG_IFUP |
@@ -860,7 +863,6 @@ static int netvsc_set_channels(struct net_device *net,
 
        memset(&device_info, 0, sizeof(device_info));
        device_info.num_chn = count;
-       device_info.ring_size = ring_size;
        device_info.send_sections = nvdev->send_section_cnt;
        device_info.send_section_size = nvdev->send_section_size;
        device_info.recv_sections = nvdev->recv_section_cnt;
@@ -975,7 +977,6 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
                rndis_filter_close(nvdev);
 
        memset(&device_info, 0, sizeof(device_info));
-       device_info.ring_size = ring_size;
        device_info.num_chn = nvdev->num_chn;
        device_info.send_sections = nvdev->send_section_cnt;
        device_info.send_section_size = nvdev->send_section_size;
@@ -1539,7 +1540,6 @@ static int netvsc_set_ringparam(struct net_device *ndev,
 
        memset(&device_info, 0, sizeof(device_info));
        device_info.num_chn = nvdev->num_chn;
-       device_info.ring_size = ring_size;
        device_info.send_sections = new_tx;
        device_info.send_section_size = nvdev->send_section_size;
        device_info.recv_sections = new_rx;
@@ -1995,7 +1995,6 @@ static int netvsc_probe(struct hv_device *dev,
 
        /* Notify the netvsc driver of the new device */
        memset(&device_info, 0, sizeof(device_info));
-       device_info.ring_size = ring_size;
        device_info.num_chn = VRSS_CHANNEL_DEFAULT;
        device_info.send_sections = NETVSC_DEFAULT_TX;
        device_info.send_section_size = NETVSC_SEND_SECTION_SIZE;
@@ -2158,11 +2157,13 @@ static int __init netvsc_drv_init(void)
 
        if (ring_size < RING_SIZE_MIN) {
                ring_size = RING_SIZE_MIN;
-               pr_info("Increased ring_size to %d (min allowed)\n",
+               pr_info("Increased ring_size to %u (min allowed)\n",
                        ring_size);
        }
-       ret = vmbus_driver_register(&netvsc_drv);
+       netvsc_ring_bytes = ring_size * PAGE_SIZE;
+       netvsc_ring_reciprocal = reciprocal_value(netvsc_ring_bytes);
 
+       ret = vmbus_driver_register(&netvsc_drv);
        if (ret)
                return ret;
 

diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index 7b637c7dd1e5fe726722779ed60434aab49a09d1..6734920633075675650f042f95dc878b2a4ffd0f 100644 (file)
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -1040,8 +1040,8 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc)
        /* Set the channel before opening.*/
        nvchan->channel = new_sc;
 
-       ret = vmbus_open(new_sc, nvscdev->ring_size * PAGE_SIZE,
-                        nvscdev->ring_size * PAGE_SIZE, NULL, 0,
+       ret = vmbus_open(new_sc, netvsc_ring_bytes,
+                        netvsc_ring_bytes, NULL, 0,
                         netvsc_channel_cb, nvchan);
        if (ret == 0)
                napi_enable(&nvchan->napi);