On Fri, Feb 26, 2016 at 8:40 PM, zhao ya <marywangran0...@gmail.com> wrote:
> From: Zhao Ya <marywangran0...@gmail.com>
> Date: Sat, 27 Feb 2016 10:06:44 +0800
> Subject: [PATCH] IPIP tunnel performance improvement
>
> bypass the logic of each packet's own neighbour creation when using
> pointopint or loopback device.
>
> Recently, in our tests, met a performance problem.
> In a large number of packets with different target IP address through
> ipip tunnel, PPS will decrease sharply.
>
> The output of perf top are as follows, __write_lock_failed is of the first:
> - 5.89% [kernel] [k] __write_lock_failed
> -__write_lock_failed a
> -_raw_write_lock_bh a
> -__neigh_create a
> -ip_finish_output a
> -ip_output a
> -ip_local_out a
>
> The neighbour subsystem will create a neighbour object for each target
> when using pointopint device. When massive amounts of packets with diff-
> erent target IP address to be xmit through a pointopint device, these
> packets will suffer the bottleneck at write_lock_bh(&tbl->lock) after
> creating the neighbour object and then inserting it into a hash-table
> at the same time.
>
> This patch correct it. Only one or little amounts of neighbour objects
> will be created when massive amounts of packets with different target IP
> address through ipip tunnel.
>
> As the result, performance will be improved.
Well, you just basically revert another bug fix:
commit 0bb4087cbec0ef74fd416789d6aad67957063057
Author: David S. Miller <da...@davemloft.net>
Date: Fri Jul 20 16:00:53 2012 -0700
ipv4: Fix neigh lookup keying over loopback/point-to-point devices.
We were using a special key "0" for all loopback and point-to-point
device neigh lookups under ipv4, but we wouldn't use that special
key for the neigh creation.
So basically we'd make a new neigh at each and every lookup :-)
This special case to use only one neigh for these device types
is of dubious value, so just remove it entirely.
Reported-by: Eric Dumazet <eric.duma...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
which would bring the neigh entries counting problem back...
Did you try to tune the neigh gc parameters for your case?
Thanks.
