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Message-ID: <469E9510.7060703@garzik.org>
Date: Wed, 18 Jul 2007 18:32:48 -0400
From: Jeff Garzik <jeff@...zik.org>
To: Brian King <brking@...ux.vnet.ibm.com>
CC: santil@...ux.vnet.ibm.com, rcjenn@...ux.vnet.ibm.com,
netdev@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: [PATCH 1/4] ibmveth: Enable TCP checksum offload
Brian King wrote:
> This patchset enables TCP checksum offload support for IPV4
> on ibmveth. This completely eliminates the generation and checking of
> the checksum for packets that are completely virtual and never
> touch a physical network. A simple TCP_STREAM netperf run on
> a virtual network with maximum mtu set yielded a ~30% increase
> in throughput. This feature is enabled by default on systems that
> support it, but can be disabled with a module option.
>
> Signed-off-by: Brian King <brking@...ux.vnet.ibm.com>
this should be controllable purely via ethtool...
> diff -puN drivers/net/ibmveth.c~ibmveth_csum_offload drivers/net/ibmveth.c
> --- linux-2.6/drivers/net/ibmveth.c~ibmveth_csum_offload 2007-07-12 08:27:47.000000000 -0500
> +++ linux-2.6-bjking1/drivers/net/ibmveth.c 2007-07-12 09:35:55.000000000 -0500
> @@ -47,6 +47,8 @@
> #include <linux/mm.h>
> #include <linux/ethtool.h>
> #include <linux/proc_fs.h>
> +#include <linux/in.h>
> +#include <linux/ip.h>
> #include <asm/semaphore.h>
> #include <asm/hvcall.h>
> #include <asm/atomic.h>
> @@ -103,12 +105,15 @@ static struct proc_dir_entry *ibmveth_pr
>
> static const char ibmveth_driver_name[] = "ibmveth";
> static const char ibmveth_driver_string[] = "IBM i/pSeries Virtual Ethernet Driver";
> +static unsigned int ibmveth_csum_offload = 1;
> #define ibmveth_driver_version "1.03"
>
> MODULE_AUTHOR("Santiago Leon <santil@...ibm.com>");
> MODULE_DESCRIPTION("IBM i/pSeries Virtual Ethernet Driver");
> MODULE_LICENSE("GPL");
> MODULE_VERSION(ibmveth_driver_version);
> +module_param_named(csum_offload, ibmveth_csum_offload, uint, 0);
> +MODULE_PARM_DESC(csum_offload, "Checksum offload (0/1). Default: 1");
>
> /* simple methods of getting data from the current rxq entry */
> static inline int ibmveth_rxq_pending_buffer(struct ibmveth_adapter *adapter)
> @@ -131,6 +136,11 @@ static inline int ibmveth_rxq_frame_leng
> return (adapter->rx_queue.queue_addr[adapter->rx_queue.index].length);
> }
>
> +static inline int ibmveth_rxq_csum_good(struct ibmveth_adapter *adapter)
> +{
> + return (adapter->rx_queue.queue_addr[adapter->rx_queue.index].csum_good);
> +}
> +
> /* setup the initial settings for a buffer pool */
> static void ibmveth_init_buffer_pool(struct ibmveth_buff_pool *pool, u32 pool_index, u32 pool_size, u32 buff_size, u32 pool_active)
> {
> @@ -684,6 +694,24 @@ static int ibmveth_start_xmit(struct sk_
> desc[0].fields.length, DMA_TO_DEVICE);
> desc[0].fields.valid = 1;
>
> + if (skb->ip_summed == CHECKSUM_PARTIAL &&
> + ip_hdr(skb)->protocol != IPPROTO_TCP && skb_checksum_help(skb)) {
> + ibmveth_error_printk("tx: failed to checksum packet\n");
> + tx_dropped++;
> + goto out;
> + }
> +
> + if (skb->ip_summed == CHECKSUM_PARTIAL) {
> + unsigned char *buf = skb_transport_header(skb) + skb->csum_offset;
> +
> + desc[0].fields.no_csum = 1;
> + desc[0].fields.csum_good = 1;
> +
> + /* Need to zero out the checksum */
> + buf[0] = 0;
> + buf[1] = 0;
> + }
> +
> if(dma_mapping_error(desc[0].fields.address)) {
> ibmveth_error_printk("tx: unable to map initial fragment\n");
> tx_map_failed++;
> @@ -702,6 +730,10 @@ static int ibmveth_start_xmit(struct sk_
> frag->size, DMA_TO_DEVICE);
> desc[curfrag+1].fields.length = frag->size;
> desc[curfrag+1].fields.valid = 1;
> + if (skb->ip_summed == CHECKSUM_PARTIAL) {
> + desc[curfrag+1].fields.no_csum = 1;
> + desc[curfrag+1].fields.csum_good = 1;
> + }
>
> if(dma_mapping_error(desc[curfrag+1].fields.address)) {
> ibmveth_error_printk("tx: unable to map fragment %d\n", curfrag);
> @@ -792,7 +824,11 @@ static int ibmveth_poll(struct net_devic
> } else {
> int length = ibmveth_rxq_frame_length(adapter);
> int offset = ibmveth_rxq_frame_offset(adapter);
> + int csum_good = ibmveth_rxq_csum_good(adapter);
> +
> skb = ibmveth_rxq_get_buffer(adapter);
> + if (csum_good)
> + skb->ip_summed = CHECKSUM_UNNECESSARY;
>
> ibmveth_rxq_harvest_buffer(adapter);
>
> @@ -962,8 +998,10 @@ static void ibmveth_poll_controller(stru
> static int __devinit ibmveth_probe(struct vio_dev *dev, const struct vio_device_id *id)
> {
> int rc, i;
> + long ret;
> struct net_device *netdev;
> struct ibmveth_adapter *adapter = NULL;
> + union ibmveth_illan_attributes set_attr, ret_attr;
>
> unsigned char *mac_addr_p;
> unsigned int *mcastFilterSize_p;
> @@ -1058,6 +1096,26 @@ static int __devinit ibmveth_probe(struc
>
> ibmveth_debug_printk("registering netdev...\n");
>
> + if (ibmveth_csum_offload) {
> + ret = h_illan_attributes(dev->unit_address, 0, 0, &ret_attr.desc);
> +
> + if (ret == H_SUCCESS && !ret_attr.fields.active_trunk &&
> + !ret_attr.fields.trunk_priority &&
> + ret_attr.fields.csum_offload_padded_pkt_support) {
> + set_attr.desc = 0;
> + set_attr.fields.tcp_csum_offload_ipv4 = 1;
> +
> + ret = h_illan_attributes(dev->unit_address, 0, set_attr.desc,
> + &ret_attr.desc);
> +
> + if (ret == H_SUCCESS)
> + netdev->features |= NETIF_F_IP_CSUM;
> + else
> + ret = h_illan_attributes(dev->unit_address, set_attr.desc,
> + 0, &ret_attr.desc);
> + }
> + }
> +
> rc = register_netdev(netdev);
>
> if(rc) {
> diff -puN drivers/net/ibmveth.h~ibmveth_csum_offload drivers/net/ibmveth.h
> --- linux-2.6/drivers/net/ibmveth.h~ibmveth_csum_offload 2007-07-12 08:27:47.000000000 -0500
> +++ linux-2.6-bjking1/drivers/net/ibmveth.h 2007-07-12 09:32:54.000000000 -0500
> @@ -67,6 +67,21 @@ static inline long h_send_logical_lan(un
> return rc;
> }
>
> +static inline long h_illan_attributes(unsigned long unit_address,
> + unsigned long reset_mask, unsigned long set_mask,
> + unsigned long *ret_attributes)
> +{
> + long rc;
> + unsigned long retbuf[PLPAR_HCALL_BUFSIZE];
> +
> + rc = plpar_hcall(H_ILLAN_ATTRIBUTES, retbuf, unit_address,
> + reset_mask, set_mask);
> +
> + *ret_attributes = retbuf[0];
> +
> + return rc;
> +}
> +
> #define h_multicast_ctrl(ua, cmd, mac) \
> plpar_hcall_norets(H_MULTICAST_CTRL, ua, cmd, mac)
>
> @@ -144,7 +159,9 @@ struct ibmveth_adapter {
> struct ibmveth_buf_desc_fields {
> u32 valid : 1;
> u32 toggle : 1;
> - u32 reserved : 6;
> + u32 reserved : 4;
> + u32 no_csum : 1;
> + u32 csum_good : 1;
> u32 length : 24;
> u32 address;
> };
> @@ -154,10 +171,30 @@ union ibmveth_buf_desc {
> struct ibmveth_buf_desc_fields fields;
> };
>
> +struct ibmveth_illan_attributes_fields {
> + u32 reserved;
> + u32 reserved2 : 18;
> + u32 csum_offload_padded_pkt_support : 1;
> + u32 reserved3 : 1;
> + u32 trunk_priority : 4;
> + u32 reserved4 : 5;
> + u32 tcp_csum_offload_ipv6 : 1;
> + u32 tcp_csum_offload_ipv4 : 1;
> + u32 active_trunk : 1;
> +};
> +
> +union ibmveth_illan_attributes {
> + u64 desc;
> + struct ibmveth_illan_attributes_fields fields;
> +};
> +
> struct ibmveth_rx_q_entry {
> u16 toggle : 1;
> u16 valid : 1;
> - u16 reserved : 14;
> + u16 reserved : 4;
> + u16 no_csum : 1;
> + u16 csum_good : 1;
> + u16 reserved2 : 8;
> u16 offset;
As a general rule, it would be nice to start moving away from bitfields
in this driver
-
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