From: Eric Dumazet <dada1@cosmosbay•com>
To: Kenny Chang <kchang@athenacr•com>
Cc: netdev@vger•kernel.org
Subject: Re: Multicast packet loss
Date: Fri, 30 Jan 2009 20:04:15 +0100 [thread overview]
Message-ID: <49834F2F.9070500@cosmosbay.com> (raw)
In-Reply-To: <49833DBC.7040607@athenacr.com>
Kenny Chang a écrit :
> Hi all,
>
> We've been having some issues with multicast packet loss, we were wondering
> if anyone knows anything about the behavior we're seeing.
>
> Background: we use multicast messaging with lots of messages per sec for
> our
> work. We recently transitioned many of our systems from an Ubuntu Dapper
> Drake
> ia32 distribution to Ubuntu Hardy Heron x86_64. Since the transition, we've
> noticed much more multicast packet loss, and we think it's related to the
> transition. Our particular theory is that it's specifically a 32 vs 64-bit
> issue.
>
> We narrowed the problem down to the attached program (mcasttest.cc). Run
> "mcasttest server" on one machine -- it'll send 500,000 messages small
> message
> to a multicast group, 50,000 messages per second. If we run "mcasttest
> client"
> on another machine, it'll receive all those messages and print a count
> at the
> end of how many messages it sees. It almost never loses any messages.
> However,
> if we run 4 copies of the client on the same machine, receiving the same
> data,
> then the programs usually sees fewer than 500,000 messages. We're
> running with:
>
> for i in $(seq 1 4); do (./mcasttest client &); done
>
> We know this because the program prints a count, but dropped packets also
> show up in ifconfig's "RX packets" section.
>
> Things we're curious about: do other people see similar problems? The
> tests
> we've done: we've tried this program on a bunch of different machines,
> all of
> which are running either dapper ia32 or hardy x86_64. Uniformly, the dapper
> machines have no problems but on certain machines, Hardy shows
> significant loss. We did some experiments on a troubled machine, varying
> the OS install, including mixed installations where the kernel was
> 64-bit and the userspace was
> 32-bit. This is what we found:
>
> On machines that exhibit this problem, the ksoftirqd process seems to be
> pegged to 100% CPU when receiving packets.
>
> Note: while we're on Ubuntu, we've tried this with other distros and
> have seen
> similar results, we just haven't tabulated them.
>
>> ----------------------------------------------------------------------------
>>
>> userland | userland arch | kernel | kernel arch |
>> mode
>> ----------------------------------------------------------------------------
>>
>> Dapper | 32 | 2.6.15-28-server | 32 | no packet
>> loss
>> Dapper | 32 | 2.6.22-generic | 32 | no packet
>> loss Dapper | 32 | 2.6.22-server | 32 | no
>> packet loss Hardy | 32 | 2.6.24-rt | 32
>> | no packet loss
>> Hardy | 32 | 2.6.24-generic | 32 | ~5% packet
>> loss
>> Hardy | 32 | 2.6.24-server | 32 | ~10%
>> packet loss
>
>> Hardy | 32 | 2.6.22-server | 64 | no packet
>> loss
>> Hardy | 32 | 2.6.24-rt | 64 | no packet
>> loss
>> Hardy | 32 | 2.6.24-generic | 64 | 14% packet
>> loss
>> Hardy | 32 | 2.6.24-server | 64 | 12% packet
>> loss
>
>> Hardy | 64 | 2.6.22-vanilla | 64 | packet loss
>> Hardy | 64 | 2.6.24-rt | 64 | ~5% packet
>> loss
>> Hardy | 64 | 2.6.24-server | 64 | ~30%
>> packet loss
>> Hardy | 64 | 2.6.24-generic | 64 | ~5% packet
>> loss
>> ----------------------------------------------------------------------------
>>
>
> It's not exactly clear what exactly the problem is but dapper shows no
> issues regardless of what we try. For hardy, userspace seem to matter:
> 2.6.24-rt kernel shows no packet loss for 32&64bit kernels, as long as
> the userspace is 32-bit.
>
> Kernel comments:
> 2.6.15-28-server: This is Ubuntu Dapper's stock kernel build.
> 2.6.24-*: This is Ubuntu Hardy's stock kernel.
> 2.6.22-{generic,server}: This is a custom, in-house kernel build, built
> for ia32.
> 2.6.22-vanilla: This is our custom, in-house kernel build, built for
> x86_64.
>
> We don't think it's related to our custom kernels, because the same
> phenomena
> show up with the Ubuntu stock kernels.
>
> Hardware:
>
> The benchmark machine We've been using is an Intel Xeon E5440 @2.83GHz
> dual-cpu quad-core with Broadcom NetXtreme II BCM5708 bnx2 networking.
>
> We've also tried AMD machines, as well as machines with Tigon3
> partno(BCM95704A6) tg3 network cards, they all show consistent behavior.
>
> Our hardy x86_64 server machines all appear to have this problem, new
> and old.
>
> On the other hand, a desktop with Intel Q6600 quad core 2.4GHz and Intel
> 82566DC GigE
> seem to work fine.
>
> All of the dapper ia32 machines have no trouble, even our older hardware.
>
>
Hi Kenny
Interesting... You forgot the mcasttest.cc program
Any chance you try a recent kernel (2.6.29-rcX) ?
Could you post "cat /proc/interrupts" results (one for working
setup, another for non working/droping setup)
next prev parent reply other threads:[~2009-01-30 19:04 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 [this message]
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
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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