From: Eric Dumazet <dada1@cosmosbay•com>
To: Kenny Chang <kchang@athenacr•com>
Cc: netdev@vger•kernel.org, "David S. Miller" <davem@davemloft•net>,
Christoph Lameter <cl@linux-foundation•org>
Subject: Re: Multicast packet loss
Date: Sun, 01 Mar 2009 18:03:12 +0100 [thread overview]
Message-ID: <49AABFD0.5090204@cosmosbay.com> (raw)
In-Reply-To: <49A8FAFF.7060104@cosmosbay.com>
Eric Dumazet a écrit :
> Kenny Chang a écrit :
>> It's been a while since I updated this thread. We've been running
>> through the different suggestions and tabulating their effects, as well
>> as trying out an Intel card. The short story is that setting affinity
>> and MSI works to some extent, and the Intel card doesn't seem to change
>> things significantly. The results don't seem consistent enough for us
>> to be able to point to a smoking gun.
>>
>> It does look like the 2.6.29-rc4 kernel performs okay with the Intel
>> card, but this is not a real-time build and it's not likely to be in a
>> supported Ubuntu distribution real soon. We've reached the point where
>> we'd like to look for an expert dedicated to work on this problem for a
>> period of time. The final result being some sort of solution to produce
>> a realtime configuration with a reasonably "aged" kernel (.24~.28) that
>> has multicast performance greater than or equal to that of 2.6.15.
>>
>> If anybody is interested in devoting some compensated time to this
>> issue, we're offering up a bounty:
>> http://www.athenacr.com/bounties/multicast-performance/
>>
>> For completeness, here's the table of our experiment results:
>>
>> ====================== ================== ========= ==========
>> =============== ============== ============== =================
>> Kernel flavor IRQ affinity *4x
>> mcasttest* *5x mcasttest* *6x mcasttest* *Mtools2* [4]_
>> ====================== ================== ========= ==========
>> =============== ============== ============== =================
>> Intel
>> e1000e
>>
>> -----------------------------------------+---------+----------+---------------+--------------+--------------+-----------------
>>
>> 2.6.24.19 rt | any |
>> OK Maybe X
>> 2.6.24.19 rt | CPU0 |
>> OK OK X
>> 2.6.24.19 generic | any |
>> X
>> 2.6.24.19 generic | CPU0 |
>> OK
>> 2.6.29-rc3 vanilla-server | any |
>> X
>> 2.6.29-rc3 vanilla-server | CPU0 |
>> OK
>> 2.6.29-rc4 vanilla-generic | any |
>> X OK
>> 2.6.29-rc4 vanilla-generic | CPU0 | OK
>> OK OK [5]_ OK
>> -----------------------------------------+---------+----------+---------------+--------------+--------------+-----------------
>>
>> Broadcom
>> BNX2
>>
>> -----------------------------------------+---------+----------+---------------+--------------+--------------+-----------------
>>
>> 2.6.24-19 rt | MSI any |
>> OK OK X
>> 2.6.24-19 rt | MSI CPU0 |
>> OK Maybe X
>> 2.6.24-19 rt | APIC any |
>> OK OK X
>> 2.6.24-19 rt | APIC CPU0 |
>> OK Maybe X
>> 2.6.24-19-bnx-latest rt | APIC CPU0 |
>> OK X
>> 2.6.24-19 server | MSI any |
>> X
>> 2.6.24-19 server | MSI CPU0 |
>> OK
>> 2.6.24-19 generic | APIC any |
>> X
>> 2.6.24-19 generic | APIC CPU0 |
>> OK
>> 2.6.27-11 generic | APIC any |
>> X
>> 2.6.27-11 generic | APIC CPU0 |
>> OK 10% drop
>> 2.6.28-8 generic | APIC any |
>> OK X
>> 2.6.28-8 generic | APIC CPU0 |
>> OK OK 0.5% drop
>> 2.6.29-rc3 vanilla-server | MSI any |
>> X
>> 2.6.29-rc3 vanilla-server | MSI CPU0 |
>> X
>> 2.6.29-rc3 vanilla-server | APIC any |
>> OK X
>> 2.6.29-rc3 vanilla-server | APIC CPU0 |
>> OK OK
>> 2.6.29-rc4 vanilla-generic | APIC any |
>> X
>> 2.6.29-rc4 vanilla-generic | APIC CPU0 |
>> OK 3% drop 10% drop X
>> ======================
>> ==================+=========+==========+===============+==============+==============+=================
>>
>> * [4] MTools2 is a test from 29West: http://www.29west.com/docs/TestNet/
>> * [5] In 5 trials, 1 of the trials dropped 2%, 4 of the trials dropped
>> nothing.
>>
>> Kenny
>>
>
> Hi Kenny
>
> I am investigating how to reduce contention (and schedule() calls) on this workload.
>
I bound NIC (gigabit BNX2) irq to cpu 0, so that oprofile results on this cpu can show us
where ksoftirqd is spending its time.
We can see scheduler at work :)
Also, one thing to note is __copy_skb_header() : 9.49 % of cpu0 time.
The problem comes from dst_clone() (6.05 % total, so 2/3 of __copy_skb_header()),
touching a highly contended cache line. (other cpus are doing the decrement of
dst refcounter)
CPU: Core 2, speed 3000.05 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted)
with a unit mask of 0x00 (Unhalted core cycles) count 100000
Samples on CPU 0
(samples for other cpus 1..7 omitted)
samples cum. samples % cum. % symbol name
23750 23750 9.8159 9.8159 try_to_wake_up
22972 46722 9.4944 19.3103 __copy_skb_header
20217 66939 8.3557 27.6660 enqueue_task_fair
14565 81504 6.0197 33.6857 sock_def_readable
13454 94958 5.5606 39.2463 task_rq_lock
13381 108339 5.5304 44.7767 resched_task
13090 121429 5.4101 50.1868 udp_queue_rcv_skb
11441 132870 4.7286 54.9154 skb_queue_tail
10109 142979 4.1781 59.0935 sock_queue_rcv_skb
10024 153003 4.1429 63.2364 __wake_up_sync
9952 162955 4.1132 67.3496 update_curr
8761 171716 3.6209 70.9705 sched_clock_cpu
7414 179130 3.0642 74.0347 rb_insert_color
7381 186511 3.0506 77.0853 select_task_rq_fair
6749 193260 2.7894 79.8747 __slab_alloc
5881 199141 2.4306 82.3053 __wake_up_common
5432 204573 2.2451 84.5504 __skb_clone
4306 208879 1.7797 86.3300 kmem_cache_alloc
3524 212403 1.4565 87.7865 place_entity
2783 215186 1.1502 88.9367 skb_clone
2576 217762 1.0647 90.0014 __udp4_lib_rcv
2430 220192 1.0043 91.0057 bnx2_poll_work
2184 222376 0.9027 91.9084 ipt_do_table
2090 224466 0.8638 92.7722 ip_route_input
1877 226343 0.7758 93.5479 __alloc_skb
1495 227838 0.6179 94.1658 native_sched_clock
1166 229004 0.4819 94.6477 __update_sched_clock
1083 230087 0.4476 95.0953 netif_receive_skb
1062 231149 0.4389 95.5343 activate_task
644 231793 0.2662 95.8004 __kmalloc_track_caller
638 232431 0.2637 96.0641 nf_iterate
549 232980 0.2269 96.2910 skb_put
next prev parent reply other threads:[~2009-03-01 17:03 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
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 [this message]
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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