From: Wes Chow <wchow@athenacr•com>
To: Eric Dumazet <dada1@cosmosbay•com>
Cc: netdev@vger•kernel.org
Subject: Re: Multicast packet loss
Date: Mon, 02 Feb 2009 16:09:33 -0500 [thread overview]
Message-ID: <4987610D.6040902@athenacr.com> (raw)
In-Reply-To: <498757AA.8010101@cosmosbay.com>
Eric Dumazet wrote:
> Wes Chow a écrit :
>> (I'm Kenny's colleague, and I've been doing the kernel builds)
>>
>> First I'd like to note that there were a lot of bnx2 NAPI changes between
>> 2.6.21 and 2.6.22. As a reminder, 2.6.21 shows tiny amounts of packet loss,
>> whereas loss in 2.6.22 is significant.
>>
>> Second, some CPU affinity info: if I do like Eric and pin all of the
>> apps onto a single CPU, I see no packet loss. Also, I do *not* see
>> ksoftirqd show up on top at all!
>>
>> If I pin half the processes on one CPU and the other half on another CPU, one
>> ksoftirqd processes shows up in top and completely pegs one CPU. My packet loss
>> in that case is significant (25%).
>>
>> Now, the strange case: if I pin 3 processes to one CPU and 1 process to
>> another, I get about 25% packet loss and ksoftirqd pins one CPU. However, one
>> of the apps takes significantly less CPU than the others, and all apps lose the
>> *exact same number of packets*. In all other situations where we see packet
>> loss, the actual number lost per application instance appears random.
>
> You see same number of packet lost because they are lost at NIC level
Understood.
I have a new observation: if I pin processes to just CPUs 0 and 1, I see
no packet loss. Pinning to 0 and 2, I do see packet loss. Pinning 2 and
3, no packet loss. 4 & 5 - no packet loss, 6 & 7 - no packet loss. Any
other combination appears to produce loss (though I have not tried all
28 combinations, this seems to be the case).
At first I thought maybe it had to do with processes pinned to the same
CPU, but different cores. The machine is a dual quad core, which means
that CPUs 0-3 should be a physical CPU, correct? Pinning to 0/2 and 0/3
produce packet loss.
I've also noticed that it does not matter which of the working pairs I
pin to. For example, pinning 5 processes in any combination on either
0/1 produce no packet loss, pinning all 5 to just CPU 0 also produces no
packet loss.
The failures are also sudden. In all of the working cases mentioned
above, I don't see ksoftirqd on top at all. But when I run 6 processes
on a single CPU, ksoftirqd shoots up to 100% and I lose a huge number of
packets.
>
> Normaly, softirq runs on same cpu (the one handling hard irq)
What determines which CPU the hard irq occurs on?
Wes
next prev parent reply other threads:[~2009-02-02 21:20 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-30 17:49 Multicast packet loss Kenny Chang
2009-01-30 19:04 ` Eric Dumazet
2009-01-30 19:17 ` Denys Fedoryschenko
2009-01-30 20:03 ` Neil Horman
2009-01-30 22:29 ` Kenny Chang
2009-01-30 22:41 ` Eric Dumazet
2009-01-31 16:03 ` Neil Horman
2009-02-02 16:13 ` Kenny Chang
2009-02-02 16:48 ` Kenny Chang
2009-02-03 11:55 ` Neil Horman
2009-02-03 15:20 ` Kenny Chang
2009-02-04 1:15 ` Neil Horman
2009-02-04 16:07 ` Kenny Chang
2009-02-04 16:46 ` Wesley Chow
2009-02-04 18:11 ` Eric Dumazet
2009-02-05 13:33 ` Neil Horman
2009-02-05 13:46 ` Wesley Chow
2009-02-05 13:29 ` Neil Horman
2009-02-01 12:40 ` Eric Dumazet
2009-02-02 13:45 ` Neil Horman
2009-02-02 16:57 ` Eric Dumazet
2009-02-02 18:22 ` Neil Horman
2009-02-02 19:51 ` Wes Chow
2009-02-02 20:29 ` Eric Dumazet
2009-02-02 21:09 ` Wes Chow [this message]
2009-02-02 21:31 ` Eric Dumazet
2009-02-03 17:34 ` Kenny Chang
2009-02-04 1:21 ` Neil Horman
2009-02-26 17:15 ` Kenny Chang
2009-02-28 8:51 ` Eric Dumazet
2009-03-01 17:03 ` Eric Dumazet
2009-03-04 8:16 ` David Miller
2009-03-04 8:36 ` Eric Dumazet
2009-03-07 7:46 ` Eric Dumazet
2009-03-08 16:46 ` Eric Dumazet
2009-03-09 2:49 ` David Miller
2009-03-09 6:36 ` Eric Dumazet
2009-03-13 21:51 ` David Miller
2009-03-13 22:30 ` Eric Dumazet
2009-03-13 22:38 ` David Miller
2009-03-13 22:45 ` Eric Dumazet
2009-03-14 9:03 ` [PATCH] net: reorder fields of struct socket Eric Dumazet
2009-03-16 2:59 ` David Miller
2009-03-16 22:22 ` Multicast packet loss Eric Dumazet
2009-03-17 10:11 ` Peter Zijlstra
2009-03-17 11:08 ` Eric Dumazet
2009-03-17 11:57 ` Peter Zijlstra
2009-03-17 15:00 ` Brian Bloniarz
2009-03-17 15:16 ` Eric Dumazet
2009-03-17 19:39 ` David Stevens
2009-03-17 21:19 ` Eric Dumazet
2009-04-03 19:28 ` Brian Bloniarz
2009-04-05 13:49 ` Eric Dumazet
2009-04-06 21:53 ` Brian Bloniarz
2009-04-06 22:12 ` Brian Bloniarz
2009-04-07 20:08 ` Brian Bloniarz
2009-04-08 8:12 ` Eric Dumazet
2009-03-09 22:56 ` Brian Bloniarz
2009-03-10 5:28 ` Eric Dumazet
2009-03-10 23:22 ` Brian Bloniarz
2009-03-11 3:00 ` Eric Dumazet
2009-03-12 15:47 ` Brian Bloniarz
2009-03-12 16:34 ` Eric Dumazet
2009-02-27 18:40 ` Christoph Lameter
2009-02-27 18:56 ` Eric Dumazet
2009-02-27 19:45 ` Christoph Lameter
2009-02-27 20:12 ` Eric Dumazet
2009-02-27 21:36 ` Eric Dumazet
2009-02-02 13:53 ` Eric Dumazet
-- strict thread matches above, loose matches on Subject: below --
2009-04-05 14:42 bmb
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