Re: [Pv-drivers] [PATCH] vmxnet3: must split too big fragments

Bhavesh Davda
2012-10-29T17:52:51Z

LGTM. Thanks for doing this! Did you do any performance testing with this patch?

Reviewed-by: Bhavesh Davda <bhavesh@vmware.com>

--
Bhavesh Davda

----- Original Message -----
> From: "Eric Dumazet" <eric.dumazet@gmail.com>
> To: "Shreyas Bhatewara" <sbhatewara@vmware.com>, "David Miller" <davem@davemloft.net>
> Cc: "VMware, Inc." <pv-drivers@vmware.com>, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "jongman heo"
> <jongman.heo@samsung.com>
> Sent: Monday, October 29, 2012 10:30:49 AM
> Subject: [Pv-drivers] [PATCH] vmxnet3: must split too big fragments
>
> From: Eric Dumazet <edumazet@google.com>
>
> vmxnet3 has a 16Kbytes limit per tx descriptor, that happened to work
> as long as we provided PAGE_SIZE fragments.
>
> Our stack can now build larger fragments, so we need to split them to
> the 16kbytes boundary.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: jongman heo <jongman.heo@samsung.com>
> Tested-by: jongman heo <jongman.heo@samsung.com>
> Cc: Shreyas Bhatewara <sbhatewara@vmware.com>
> ---
> drivers/net/vmxnet3/vmxnet3_drv.c | 65
> +++++++++++++++++++---------
> 1 file changed, 45 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c
> b/drivers/net/vmxnet3/vmxnet3_drv.c
> index ce9d4f2..0ae1bcc 100644
> --- a/drivers/net/vmxnet3/vmxnet3_drv.c
> +++ b/drivers/net/vmxnet3/vmxnet3_drv.c
> @@ -744,28 +744,43 @@ vmxnet3_map_pkt(struct sk_buff *skb, struct
> vmxnet3_tx_ctx *ctx,
>
> for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
> const struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[i];
> + u32 buf_size;
>
> - tbi = tq->buf_info + tq->tx_ring.next2fill;
> - tbi->map_type = VMXNET3_MAP_PAGE;
> - tbi->dma_addr = skb_frag_dma_map(&adapter->pdev->dev, frag,
> - 0, skb_frag_size(frag),
> - DMA_TO_DEVICE);
> + buf_offset = 0;
> + len = skb_frag_size(frag);
> + while (len) {
> + tbi = tq->buf_info + tq->tx_ring.next2fill;
> + if (len < VMXNET3_MAX_TX_BUF_SIZE) {
> + buf_size = len;
> + dw2 |= len;
> + } else {
> + buf_size = VMXNET3_MAX_TX_BUF_SIZE;
> + /* spec says that for TxDesc.len, 0 == 2^14 */
> + }
> + tbi->map_type = VMXNET3_MAP_PAGE;
> + tbi->dma_addr = skb_frag_dma_map(&adapter->pdev->dev, frag,
> + buf_offset, buf_size,
> + DMA_TO_DEVICE);
>
> - tbi->len = skb_frag_size(frag);
> + tbi->len = buf_size;
>
> - gdesc = tq->tx_ring.base + tq->tx_ring.next2fill;
> - BUG_ON(gdesc->txd.gen == tq->tx_ring.gen);
> + gdesc = tq->tx_ring.base + tq->tx_ring.next2fill;
> + BUG_ON(gdesc->txd.gen == tq->tx_ring.gen);
>
> - gdesc->txd.addr = cpu_to_le64(tbi->dma_addr);
> - gdesc->dword[2] = cpu_to_le32(dw2 | skb_frag_size(frag));
> - gdesc->dword[3] = 0;
> + gdesc->txd.addr = cpu_to_le64(tbi->dma_addr);
> + gdesc->dword[2] = cpu_to_le32(dw2);
> + gdesc->dword[3] = 0;
>
> - dev_dbg(&adapter->netdev->dev,
> - "txd[%u]: 0x%llu %u %u\n",
> - tq->tx_ring.next2fill, le64_to_cpu(gdesc->txd.addr),
> - le32_to_cpu(gdesc->dword[2]), gdesc->dword[3]);
> - vmxnet3_cmd_ring_adv_next2fill(&tq->tx_ring);
> - dw2 = tq->tx_ring.gen << VMXNET3_TXD_GEN_SHIFT;
> + dev_dbg(&adapter->netdev->dev,
> + "txd[%u]: 0x%llu %u %u\n",
> + tq->tx_ring.next2fill, le64_to_cpu(gdesc->txd.addr),
> + le32_to_cpu(gdesc->dword[2]), gdesc->dword[3]);
> + vmxnet3_cmd_ring_adv_next2fill(&tq->tx_ring);
> + dw2 = tq->tx_ring.gen << VMXNET3_TXD_GEN_SHIFT;
> +
> + len -= buf_size;
> + buf_offset += buf_size;
> + }
> }
>
> ctx->eop_txd = gdesc;
> @@ -886,6 +901,18 @@ vmxnet3_prepare_tso(struct sk_buff *skb,
> }
> }
>
> +static int txd_estimate(const struct sk_buff *skb)
> +{
> + int count = VMXNET3_TXD_NEEDED(skb_headlen(skb)) + 1;
> + int i;
> +
> + for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
> + const struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[i];
> +
> + count += VMXNET3_TXD_NEEDED(skb_frag_size(frag));
> + }
> + return count;
> +}
>
> /*
> * Transmits a pkt thru a given tq
> @@ -914,9 +941,7 @@ vmxnet3_tq_xmit(struct sk_buff *skb, struct
> vmxnet3_tx_queue *tq,
> union Vmxnet3_GenericDesc tempTxDesc;
> #endif
>
> - /* conservatively estimate # of descriptors to use */
> - count = VMXNET3_TXD_NEEDED(skb_headlen(skb)) +
> - skb_shinfo(skb)->nr_frags + 1;
> + count = txd_estimate(skb);
>
> ctx.ipv4 = (vlan_get_protocol(skb) == cpu_to_be16(ETH_P_IP));
>
>
>
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