svn commit: r303626 - in head/sys: netinet netinet6

[hiren panchasara]

On 08/01/16 at 05:02P, Andrew Gallatin wrote:
> Author: gallatin
> Date: Mon Aug  1 17:02:21 2016
> New Revision: 303626
> URL: https://svnweb.freebsd.org/changeset/base/303626
> 
> Log:
>   Rework IPV6 TCP path MTU discovery to match IPv4
>   
>   - Re-write tcp_ctlinput6() to closely mimic the IPv4 tcp_ctlinput()
>   
>   - Now that tcp_ctlinput6() updates t_maxseg, we can allow ip6_output()
>     to send TCP packets without looking at the tcp host cache for every
>     single transmit.
>   
>   - Make the icmp6 code mimic the IPv4 code & avoid returning
>     PRC_HOSTDEAD because it is so expensive.
>   
>   Without these changes in place, every TCP6 pmtu discovery or host
>   unreachable ICMP resulted in a call to in6_pcbnotify() which walks the
>   tcbinfo table with the write lock held.  Because the tcbinfo table is
>   shared between IPv4 and IPv6, this causes huge scalabilty issues on
>   servers with lots of (~100K) TCP connections, to the point where even
>   a small percent of IPv6 traffic had a disproportionate impact on
>   overall throughput.
>   
>   Reviewed by:	bz, rrs, ae (all earlier versions), lstewart (in Netflix's tree)
>   Sponsored by:		Netflix
>   Differential Revision:	https://reviews.freebsd.org/D7272

Drew,

What do you think about getting this into stable/11?

Cheers,
Hiren
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