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GET /api/patches/744426/?format=api
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{
    "id": 744426,
    "url": "http://patchwork.ozlabs.org/api/patches/744426/?format=api",
    "web_url": "http://patchwork.ozlabs.org/project/intel-wired-lan/patch/20170328164703.12688.90760.stgit@john-Precision-Tower-5810/",
    "project": {
        "id": 46,
        "url": "http://patchwork.ozlabs.org/api/projects/46/?format=api",
        "name": "Intel Wired Ethernet development",
        "link_name": "intel-wired-lan",
        "list_id": "intel-wired-lan.osuosl.org",
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    "msgid": "<20170328164703.12688.90760.stgit@john-Precision-Tower-5810>",
    "list_archive_url": null,
    "date": "2017-03-28T16:47:03",
    "name": "ixgbe: delay tail write to every 'n' packets",
    "commit_ref": null,
    "pull_url": null,
    "state": "accepted",
    "archived": false,
    "hash": "635d62bac1743a1a770d5b71d9e956c5e9753942",
    "submitter": {
        "id": 20028,
        "url": "http://patchwork.ozlabs.org/api/people/20028/?format=api",
        "name": "John Fastabend",
        "email": "john.fastabend@gmail.com"
    },
    "delegate": {
        "id": 68,
        "url": "http://patchwork.ozlabs.org/api/users/68/?format=api",
        "username": "jtkirshe",
        "first_name": "Jeff",
        "last_name": "Kirsher",
        "email": "jeffrey.t.kirsher@intel.com"
    },
    "mbox": "http://patchwork.ozlabs.org/project/intel-wired-lan/patch/20170328164703.12688.90760.stgit@john-Precision-Tower-5810/mbox/",
    "series": [],
    "comments": "http://patchwork.ozlabs.org/api/patches/744426/comments/",
    "check": "pending",
    "checks": "http://patchwork.ozlabs.org/api/patches/744426/checks/",
    "tags": {},
    "related": [],
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        "From": "John Fastabend <john.fastabend@gmail.com>",
        "X-Google-Original-From": "John Fastabend <john.r.fastabend@intel.com>",
        "To": "john.fastabend@gmail.com, alexander.duyck@gmail.com",
        "Date": "Tue, 28 Mar 2017 09:47:03 -0700",
        "Message-ID": "<20170328164703.12688.90760.stgit@john-Precision-Tower-5810>",
        "User-Agent": "StGit/0.17.1-dirty",
        "MIME-Version": "1.0",
        "Cc": "intel-wired-lan@lists.osuosl.org, u9012063@gmail.com",
        "Subject": "[Intel-wired-lan] [PATCH] ixgbe: delay tail write to every 'n'\n\tpackets",
        "X-BeenThere": "intel-wired-lan@lists.osuosl.org",
        "X-Mailman-Version": "2.1.18-1",
        "Precedence": "list",
        "List-Id": "Intel Wired Ethernet Linux Kernel Driver Development\n\t<intel-wired-lan.lists.osuosl.org>",
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        "Errors-To": "intel-wired-lan-bounces@lists.osuosl.org",
        "Sender": "\"Intel-wired-lan\" <intel-wired-lan-bounces@lists.osuosl.org>"
    },
    "content": "Current XDP implementation hits the tail on every XDP_TX return\ncode. This patch changes driver behavior to only hit the tail after\npacket processing is complete.\n\nWith this patch I can run XDP drop programs @ 14+Mpps and XDP_TX\nprograms are at ~13.5Mpps.\n\nSigned-off-by: John Fastabend <john.r.fastabend@intel.com>\n---\n drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   28 +++++++++++++++----------\n 1 file changed, 17 insertions(+), 11 deletions(-)",
    "diff": "diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c\nindex cd7eefd..750b204 100644\n--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c\n+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c\n@@ -2284,6 +2284,7 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,\n \tunsigned int mss = 0;\n #endif /* IXGBE_FCOE */\n \tu16 cleaned_count = ixgbe_desc_unused(rx_ring);\n+\tbool xdp_xmit = false;\n \n \twhile (likely(total_rx_packets < budget)) {\n \t\tunion ixgbe_adv_rx_desc *rx_desc;\n@@ -2323,10 +2324,12 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,\n \t\t}\n \n \t\tif (IS_ERR(skb)) {\n-\t\t\tif (PTR_ERR(skb) == -IXGBE_XDP_TX)\n+\t\t\tif (PTR_ERR(skb) == -IXGBE_XDP_TX) {\n+\t\t\t\txdp_xmit = true;\n \t\t\t\tixgbe_rx_buffer_flip(rx_ring, rx_buffer, size);\n-\t\t\telse\n+\t\t\t} else {\n \t\t\t\trx_buffer->pagecnt_bias++;\n+\t\t\t}\n \t\t\ttotal_rx_packets++;\n \t\t\ttotal_rx_bytes += size;\n \t\t} else if (skb) {\n@@ -2394,6 +2397,16 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,\n \t\ttotal_rx_packets++;\n \t}\n \n+\tif (xdp_xmit) {\n+\t\tstruct ixgbe_ring *ring = adapter->xdp_ring[smp_processor_id()];\n+\n+\t\t/* Force memory writes to complete before letting h/w\n+\t\t * know there are new descriptors to fetch.\n+\t\t */\n+\t\twmb();\n+\t\twritel(ring->next_to_use, ring->tail);\n+\t}\n+\n \tu64_stats_update_begin(&rx_ring->syncp);\n \trx_ring->stats.packets += total_rx_packets;\n \trx_ring->stats.bytes += total_rx_bytes;\n@@ -8239,14 +8252,8 @@ static int ixgbe_xmit_xdp_ring(struct ixgbe_adapter *adapter,\n \ttx_desc->read.olinfo_status =\n \t\tcpu_to_le32(len << IXGBE_ADVTXD_PAYLEN_SHIFT);\n \n-\t/* Force memory writes to complete before letting h/w know there\n-\t * are new descriptors to fetch.  (Only applicable for weak-ordered\n-\t * memory model archs, such as IA-64).\n-\t *\n-\t * We also need this memory barrier to make certain all of the\n-\t * status bits have been updated before next_to_watch is written.\n-\t */\n-\twmb();\n+\t/* Avoid any potential race with xdp_xmit and cleanup */\n+\tsmp_wmb();\n \n \t/* set next_to_watch value indicating a packet is present */\n \ti++;\n@@ -8256,7 +8263,6 @@ static int ixgbe_xmit_xdp_ring(struct ixgbe_adapter *adapter,\n \ttx_buffer->next_to_watch = tx_desc;\n \tring->next_to_use = i;\n \n-\twritel(i, ring->tail);\n \treturn IXGBE_XDP_TX;\n }\n \n",
    "prefixes": []
}