From: Jesper Dangaard Brouer <brouer@redhat•com>
To: David Miller <davem@davemloft•net>
Cc: eric.dumazet@gmail•com, netdev@vger•kernel.org,
brouer@redhat•com, xiyou.wangcong@gmail•com
Subject: Re: [net-next PATCH] net: reduce cycles spend on ICMP replies that gets rate limited
Date: Sat, 7 Jan 2017 11:31:33 +0100 [thread overview]
Message-ID: <20170107113133.227f3c29@redhat.com> (raw)
In-Reply-To: <20170106.221042.1641025960219244932.davem@davemloft.net>
On Fri, 06 Jan 2017 22:10:42 -0500 (EST)
David Miller <davem@davemloft•net> wrote:
> BTW Eric, you asked about kmalloc() allocation, you were CC:'d in the
> patch which did this :-)
>
> commit 9a99d4a50cb8ce516adf0f2436138d4c8e6e4535
> Author: Cong Wang <amwang@redhat•com>
> Date: Sun Jun 2 15:00:52 2013 +0000
>
> icmp: avoid allocating large struct on stack
>
> struct icmp_bxm is a large struct, reduce stack usage
> by allocating it on heap.
>
> Cc: Eric Dumazet <eric.dumazet@gmail•com>
> Cc: Joe Perches <joe@perches•com>
> Cc: David S. Miller <davem@davemloft•net>
> Signed-off-by: Cong Wang <amwang@redhat•com>
> Signed-off-by: David S. Miller <davem@davemloft•net>
Did a quick revert, and tested again. It is not the major bottleneck,
but we do save something. The major bottleneck is still the call to
__ip_route_output_key_hash (invoked by icmp_route_lookup).
Single flow improvement from 1719182 pps to 1783368 pps.
- 64186 pps
- (1/1783368-1/1719182)*10^9 = -20.93 nanosec
* 4GHz approx = 20.93*4 = 83.72 cycles
The optimal SLUB fast-path on this machine is 54 cycles(tsc) 13.557 ns,
thus the saving is actually higher than expected. But low compared to
avoiding the icmp_route_lookup.
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2017-01-07 10:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-06 17:39 [net-next PATCH] net: reduce cycles spend on ICMP replies that gets rate limited Jesper Dangaard Brouer
2017-01-06 19:40 ` Eric Dumazet
2017-01-06 22:08 ` Eric Dumazet
2017-01-07 3:10 ` David Miller
2017-01-07 10:31 ` Jesper Dangaard Brouer [this message]
2017-01-07 9:28 ` Jesper Dangaard Brouer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170107113133.227f3c29@redhat.com \
--to=brouer@redhat$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=eric.dumazet@gmail$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
--cc=xiyou.wangcong@gmail$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox