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Message-ID: <58916AFC.8030901@gmail.com>
Date: Tue, 31 Jan 2017 20:58:36 -0800
From: John Fastabend <john.fastabend@...il.com>
To: Alexei Starovoitov <ast@...com>, bjorn.topel@...il.com,
jasowang@...hat.com, alexander.duyck@...il.com, brouer@...hat.com
Cc: john.r.fastabend@...el.com, netdev@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] ixgbe: add af_packet direct copy support
On 17-01-30 06:53 PM, Alexei Starovoitov wrote:
> On 1/27/17 1:34 PM, John Fastabend wrote:
>> + h2 = page_address(rx_buffer->page) + rx_buffer->page_offset - hdrlen;
>> + eth = page_address(rx_buffer->page) + rx_buffer->page_offset,
>
> I don't think it compiles ;)
Well that is what I get for doing some last minute checkpatch fixes
and not doing a build test before sending it out. Oh well just an RFC
to get some general feedback.
>
>> + /* This indicates a bug in ixgbe leaving for testing purposes */
>> + WARN_ON(TP_STATUS_USER & h2->tp_status);
>> + len = le16_to_cpu(rx_desc->wb.upper.length);
>> + h2->tp_len = len;
>> + h2->tp_snaplen = len;
>> + h2->tp_mac = ALIGN(TPACKET_ALIGN(TPACKET2_HDRLEN), L1_CACHE_BYTES);
>> + h2->tp_net = h2->tp_mac + ETH_HLEN;
>> + h2->tp_sec = div_s64_rem(ns, NSEC_PER_SEC, &rem);
>> + h2->tp_nsec = rem;
>> +
>> + sll = (void *)h2 + TPACKET_ALIGN(sizeof(struct tpacket2_hdr));
>> + sll->sll_halen = ETH_HLEN;
>> + memcpy(sll->sll_addr, eth->h_source, ETH_ALEN);
>> + sll->sll_family = AF_PACKET;
>> + sll->sll_hatype = rx_ring->netdev->type;
>> + sll->sll_protocol = eth->h_proto;
>> + sll->sll_pkttype = PACKET_HOST;
>> + sll->sll_ifindex = rx_ring->netdev->ifindex;
>
> performance wise it looks very expensive to do all these header copies
> and integer divide for every packet.
> I think unless we move to new dumb and simple header format
> performance of this approach is not going to be satisfactory.
>
Sure I'm not opposed to moving to a v4 in fact I think it would help
in a lot of ways. I'll try to fire off some benchmarks and then move
to a v4 to see how that works out.
.John
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