netdev - Re: SO_REUSEPORT - can it be done in kernel?

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Message-ID: <1298904783.2941.412.camel@edumazet-laptop>
Date:	Mon, 28 Feb 2011 15:53:03 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	David Miller <davem@...emloft.net>, rick.jones2@...com,
	therbert@...gle.com, wsommerfeld@...gle.com,
	daniel.baluta@...il.com, netdev@...r.kernel.org
Subject: Re: SO_REUSEPORT - can it be done in kernel?

Le lundi 28 février 2011 à 14:32 +0100, Eric Dumazet a écrit :
> Le lundi 28 février 2011 à 19:36 +0800, Herbert Xu a écrit :
> > On Sun, Feb 27, 2011 at 07:06:14PM +0800, Herbert Xu wrote:
> > > I'm working on this right now.
> > 
> > OK I think I was definitely on the right track.  With the send
> > patch made lockless I now get numbers which are even better than
> > those obtained with running named with multiple sockets.  That's
> > right, a single socket is now faster than what multiple sockets
> > were without the patch (of course, multiple sockets may still
> > faster with the patch vs. a single socket for obvious reasons,
> > but I couldn't measure any significant difference).
> > 
> > Also worthy of note is that prior to the patch all CPUs showed
> > idleness (lazy bastards!), with the patch they're all maxed out.
> > 
> > In retrospect, the idleness was simply the result of the socket
> > lock scheduling away and was an indication of lock contention.
> > 
> 
> Now, input path can run without finding socket locked by xmit path, so
> skb are queued into receive queue, not backlog one.
> 
> > Here are the patches I used.  Please don't them yet as I intend
> > to clean them up quite a bit.
> > 
> > But please do test them heavily, especially if you have an AMD
> > NUMA machine as that's where scalability problems really show
> > up.  Intel tends to be a lot more forgiving.  My last AMD machine
> > blew up years ago :)
> 
> I am going to test them, thanks !
> 

First "sending only" tests on my 2x4x2 machine (two E5540@...3GHz, quad
core, hyper threaded, NUMA kernel)

16 threads, each one sending 100.000 UDP frames using a _shared_ socket

I use the same destination IP, so suffer a bit of dst refcount
contention.

(to dummy0 device to avoid contention on qdisc and device)
# ip ro get 10.2.2.21
10.2.2.21 dev dummy0  src 10.2.2.2 
    cache 

LOCKDEP enabled kernel

Before :

time ./udpflood -f -t 16 -l 100000 10.2.2.21

real	0m42.749s
user	0m1.010s
sys	1m38.039s

After :

time ./udpflood -f -t 16 -l 100000 10.2.2.21

real	0m1.167s
user	0m0.488s
sys	0m17.373s


With one thread only and 16*100000 frames :
# time ./udpflood -f -l 1600000 10.2.2.21

real	0m9.318s
user	0m0.238s
sys	0m9.052s

(We have some false sharing on atomic fields in struct file and socket,
but nothing to worry about.)

With LOCKDEP OFF :

16 threads :

# time ./udpflood -f -t 16 -l 100000 10.2.2.21

real	0m0.718s
user	0m0.376s
sys	0m10.963s

1 thread :

# time ./udpflood -f -l 1600000 10.2.2.21

real	0m1.514s
user	0m0.153s
sys	0m1.357s


"perf record/report" results for the 16 threads case (no lockdep)

# Events: 389K cpu-clock-msecs
#
# Overhead      Command        Shared Object                               Symbol
# ........  ...........  ...................  ...................................
#
     9.03%     udpflood  [kernel.kallsyms]    [k] sock_wfree
     8.58%     udpflood  [kernel.kallsyms]    [k] __ip_route_output_key
     8.52%     udpflood  [kernel.kallsyms]    [k] sock_alloc_send_pskb
     7.46%     udpflood  [kernel.kallsyms]    [k] sock_def_write_space
     6.76%     udpflood  [kernel.kallsyms]    [k] __xfrm_lookup
     6.18%      swapper  [kernel.kallsyms]    [k] acpi_idle_enter_bm
     5.66%     udpflood  [kernel.kallsyms]    [k] dst_release
     4.96%     udpflood  [kernel.kallsyms]    [k] udp_sendmsg
     3.48%     udpflood  [kernel.kallsyms]    [k] fget_light
     2.75%     udpflood  [kernel.kallsyms]    [k] sock_tx_timestamp
     2.40%     udpflood  [kernel.kallsyms]    [k] __ip_make_skb
     2.36%     udpflood  [kernel.kallsyms]    [k] fput
     1.87%      swapper  [kernel.kallsyms]    [k] _raw_spin_unlock_irqrestore
     1.81%     udpflood  [kernel.kallsyms]    [k] inet_sendmsg
     1.53%     udpflood  [kernel.kallsyms]    [k] sys_sendto
     1.50%     udpflood  [kernel.kallsyms]    [k] ip_finish_output
     1.31%     udpflood  [kernel.kallsyms]    [k] csum_partial_copy_generic
     1.30%     udpflood  udpflood             [.] do_thread
     1.28%     udpflood  [kernel.kallsyms]    [k] __ip_append_data
     1.08%     udpflood  [kernel.kallsyms]    [k] __memset
     1.05%     udpflood  [kernel.kallsyms]    [k] ip_route_output_flow
     0.91%     udpflood  [kernel.kallsyms]    [k] kfree
     0.88%     udpflood  [vdso]               [.] 0xffffe430
     0.83%     udpflood  [kernel.kallsyms]    [k] copy_user_generic_string
     0.78%     udpflood  libc-2.3.4.so        [.] __GI_memcpy
     0.77%     udpflood  [kernel.kallsyms]    [k] ia32_sysenter_target


What do you suggest to perform a bind based test ?



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