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Message-ID: <4AA7E082.90807@gmail.com>
Date: Wed, 09 Sep 2009 19:06:10 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Christoph Lameter <cl@...ux-foundation.org>
CC: netdev@...r.kernel.org
Subject: Re: UDP regression with packets rates < 10k per sec
Christoph Lameter a écrit :
> On Wed, 9 Sep 2009, Eric Dumazet wrote:
>
>> Christoph Lameter a ?crit :
>>> On Wed, 9 Sep 2009, Eric Dumazet wrote:
>>>
>>>> In order to reproduce this here, could you tell me if you use
>>>>
>>>> Producer linux-2.6.22 -> Receiver 2.6.22
>>>> Producer linux-2.6.31 -> Receiver 2.6.31
>>> I use the above setup.
>> Then frames are sent on wire but not received
>>
>> (they are received via mc loop, internal stack magic)
>
> We are talking about two machines running 2.6.22 or 2.6.31. There is no
> magic mc loop between the two machines. -L was not used.
>
>> # ./mcast -L -n1 -r 10000
>> WARNING: Multiple active ethernet devices. Using local address 192.168.0.1
>> Receiver: Listening to control channel 239.0.192.1
>> Receiver: Subscribing to 1 MC addresses 239.0.192-254.2-254 offset 0 origin 192.168.0.1
>> Sender: Sending 10000 msgs/ch/sec on 1 channels. Probe interval=0.001-1 sec.
>>
>> TotalMsg Lost SeqErr TXDrop Msg/Sec KB/Sec Min/us Avg/us Max/us StdDv
>> 100000 0 0 0 10000 3000.0 7.84 8.89 10.51 0.66
>
> These are loopback latencies... Dont use -L
>
>> # uname -a
>> Linux erd 2.6.30.5 #2 SMP Mon Sep 7 17:15:43 CEST 2009 i686 i686 i386 GNU/Linux
>>
>>
>>
>> I tried an old kernel on same hardware :
>>
>> # ./mcast -L -n1 -r 10000
>> WARNING: Multiple active ethernet devices. Using local address 55.225.18.6
>> Receiver: Listening to control channel 239.0.192.1
>> Receiver: Subscribing to 1 MC addresses 239.0.192-254.2-254 offset 0 origin 55.225.18.6
>> Sender: Sending 10000 msgs/ch/sec on 1 channels. Probe interval=0.001-1 sec.
>>
>> TotalMsg Lost SeqErr TXDrop Msg/Sec KB/Sec Min/us Avg/us Max/us StdDv
>> 99999 0 0 0 9998 0.0 9.00 9.95 14.50 1.56
>>
>> Linux erd 2.6.9-55.ELsmp #1 SMP Fri Apr 20 17:03:35 EDT 2007 i686 i686 i386 GNU/Linux
>>
>> So my numbers seem much better than yours...
>
> These are loopback numbers. Why is 2.6.9 so high? The regression show at
> less than 10k.
>
> Could you use real NICs? With multiple TX queues and all the other cool
> stuff? And run at lower packet rates?
well, on your mono-flow test, multiqueue wont help anyway.
>
> My loopback numbers also show the same trends.
>
> 2.6.22:
>
> mcast -Ln1
> TotalMsg Lost SeqErr TXDrop Msg/Sec KB/Sec Min/us Avg/us Max/us StdDv
> 101 0 0 0 10 3.0 5.47 5.74 7.00 0.43
>
> mcast -Ln1 -r10000
> TotalMsg Lost SeqErr TXDrop Msg/Sec KB/Sec Min/us Avg/us Max/us StdDv
> 100000 0 0 0 10000 3000.0 5.97 6.11 6.40 0.13
>
>
> 2.6.31-rc9
>
> mcast -Ln1
> TotalMsg Lost SeqErr TXDrop Msg/Sec KB/Sec Min/us Avg/us Max/us StdDv
> 100 0 0 0 10 3.0 13.26 13.45 13.56 0.09
>
> mcast -Ln1 -r10000
> TotalMsg Lost SeqErr TXDrop Msg/Sec KB/Sec Min/us Avg/us Max/us StdDv
> 100000 0 0 0 10000 3000.0 5.70 5.82 5.91 0.07
>
>
> So 2.6.22 is better at 10 msgs per second. 2.6.31 is slightly better at
> 10k.
Unfortunatly there is too much noise on this test
# uname -a
Linux nag001 2.6.26-2-amd64 #1 SMP Fri Mar 27 04:02:59 UTC 2009 x86_64 GNU/Linux
# ./mcast -Ln1 -C
WARNING: Multiple active ethernet devices. Using local address 55.225.18.110
Receiver: Listening to control channel 239.0.192.1
Receiver: Subscribing to 1 MC addresses 239.0.192-254.2-254 offset 0 origin 55.225.18.110
Sender: Sending 10 msgs/ch/sec on 1 channels. Probe interval=0.001-1 sec.
TotalMsg Lost SeqErr TXDrop Msg/Sec KB/Sec Min/us Avg/us Max/us StdDv
100 0 0 0 10 0.0 8.78 10.56 18.20 2.62
100 0 0 0 10 3.0 8.60 9.33 9.88 0.45
101 0 0 0 10 3.0 8.42 9.47 11.53 0.85
100 0 0 0 10 3.0 8.37 10.19 14.85 1.74
101 0 0 0 10 3.0 8.86 11.23 18.00 3.11
100 0 0 0 10 3.0 8.43 9.72 11.48 0.82
101 0 0 0 10 3.0 9.02 29.78 210.25 60.16
100 0 0 0 10 3.0 8.47 10.27 11.69 0.99
100 0 0 0 10 3.0 9.21 10.16 12.15 0.84
101 0 0 0 10 3.0 8.46 10.65 17.88 2.64
101 0 0 0 10 3.0 8.65 10.00 11.32 0.86
100 0 0 0 10 3.0 8.98 9.71 10.77 0.58
100 0 0 0 10 3.0 8.38 11.73 19.06 3.74
Also I believe you hit scheduler artefact at very low rate,
since there are two tasks that are considered as coupled.
Check commit 6f3d09291b4982991680b61763b2541e53e2a95f
sched, net: socket wakeups are sync
'sync' wakeups are a hint towards the scheduler that (certain)
networking related wakeups likely create coupling between tasks.
Signed-off-by: Ingo Molnar <mingo@...e.hu>
diff --git a/net/core/sock.c b/net/core/sock.c
index 09cb3a7..2654c14 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1621,7 +1621,7 @@ static void sock_def_readable(struct sock *sk, int len)
{
read_lock(&sk->sk_callback_lock);
if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
- wake_up_interruptible(sk->sk_sleep);
+ wake_up_interruptible_sync(sk->sk_sleep);
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
read_unlock(&sk->sk_callback_lock);
}
@@ -1635,7 +1635,7 @@ static void sock_def_write_space(struct sock *sk)
*/
if ((atomic_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf) {
if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
- wake_up_interruptible(sk->sk_sleep);
+ wake_up_interruptible_sync(sk->sk_sleep);
/* Should agree with poll, otherwise some programs break */
if (sock_writeable(sk))
--
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