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Date: Sat, 30 Nov 2013 14:04:20 +0000 From: Thomas Graf <tgraf@...g.ch> To: Florian Westphal <fw@...len.de> Cc: jesse@...ira.com, davem@...emloft.net, dev@...nvswitch.org, netdev@...r.kernel.org, dborkman@...hat.com, ffusco@...hat.com, fleitner@...hat.com, eric.dumazet@...il.com, bhutchings@...arflare.com Subject: Re: [net-next 3/7] openvswitch: Enable memory mapped Netlink i/o On 11/30/13 at 01:35pm, Florian Westphal wrote: > Thomas Graf <tgraf@...g.ch> wrote: > > Benchmark > > * pktgen -> ovs internal port > > * 5M pkts, 5M flows > > * 4 threads, 8 cores > > > > Before: > > Result: OK: 67418743(c67108212+d310530) usec, 5000000 (9000byte,0frags) > > 74163pps 5339Mb/sec (5339736000bps) errors: 0 > [..] > > After: > > Result: OK: 24229690(c24127165+d102524) usec, 5000000 (9000byte,0frags) > > 206358pps 14857Mb/sec (14857776000bps) errors: 0 > > I'm curious. Is the 'old' value with skb_zerocopy() or without? > Does ovs-vswitchd 'read-access' the entire packet or just e.g. the > header? > > I ask because in netfilter nfqueue tests I could not see any difference > between 'zerocopy' vs. mmap in the receive-path tests I made a while > back. The numbers quoted do not involve any zerocopy at all. It's a pure original vs. mmap comparison. I expect the numbers to grow even more once we get rid of the immediate ofpbuf copy in user space. Zerocopy as implemened right now does not provide much gains on top of mmap. We have no way yet to inject the skb frags into the ring so we are forced to copy the data. The mapped skb is simply a buffer with a tremendous tailroom to the zerocopy code. Eventually we can find a way to make the skb frags shared and link them to the ring buffer and avoid the copy. This would especially make sense if we add GSO support to openvswitch user space as nfqueue provides and avoid the segmentation before the upcall. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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