hyperv/hn: Avoid mbuf cluster allocation on reception path, if the packet is small
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Authored by sepherosa_gmail.com on Jan 11 2016, 5:38 AM.

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kmacy
howard0su_gmail.com
honzhan_microsoft.com
decui_microsoft.com
delphij
royger
adrian

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network

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rS293721: hyperv/hn: Avoid mbuf cluster allocation, if the packet is small.

Summary

This gives me ~200Mbps improvement, when running iperf3 sending test w/ 16 connections.

While I'm here, nuke the unnecessary pkthdr.csum_flags zeroing out.

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If no objection comes, this will be committed this week.

You should explain more why the change improves performance more dramatically when you commit. other than that, it's fine!

This revision is now accepted and ready to land.Jan 11 2016, 6:48 AM

In D4853#103167, @adrian wrote:

You should explain more why the change improves performance more dramatically when you commit. other than that, it's fine!

Sure, thanks.

jtl added a subscriber: jtl.Jan 12 2016, 1:50 AM

jtl added inline comments.

sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
475	Is there a reason this is read/write?
1036	Do you need an atomic operation here to guarantee accurate statistics? (And, even if you do, is it that important?)