From: Federico Parola <fede.parola@hotmail.it>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: xdp-newbies@vger.kernel.org
Subject: Re: Multi-core scalability problems
Date: Thu, 15 Oct 2020 14:04:51 +0200 [thread overview]
Message-ID: <VI1PR04MB3104487E7F503BEEE13AE7999E020@VI1PR04MB3104.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <20201014162636.39c2ba14@carbon>
On 14/10/20 16:26, Jesper Dangaard Brouer wrote:
> On Wed, 14 Oct 2020 14:17:46 +0200
> Federico Parola <fede.parola@hotmail.it> wrote:
>
>> On 14/10/20 11:15, Jesper Dangaard Brouer wrote:
>>> On Wed, 14 Oct 2020 08:56:43 +0200
>>> Federico Parola <fede.parola@hotmail.it> wrote:
>>>
>>> [...]
>>>>> Can you try to use this[2] tool:
>>>>> ethtool_stats.pl --dev enp101s0f0
>>>>>
>>>>> And notice if there are any strange counters.
>>>>>
>>>>>
>>>>> [2]https://github.com/netoptimizer/network-testing/blob/master/bin/ethtool_stats.pl
>>>>> My best guess is that you have Ethernet flow-control enabled.
>>>>> Some ethtool counter might show if that is the case.
>>>>>
>>>> Here are the results of the tool:
>>>>
>>>>
>>>> 1 FLOW:
>>>>
>>>> Show adapter(s) (enp101s0f0) statistics (ONLY that changed!)
>>>> Ethtool(enp101s0f0) stat: 35458700 ( 35,458,700) <= port.fdir_sb_match /sec
>>>> Ethtool(enp101s0f0) stat: 2729223958 ( 2,729,223,958) <= port.rx_bytes /sec
>>>> Ethtool(enp101s0f0) stat: 7185397 ( 7,185,397) <= port.rx_dropped /sec
>>>> Ethtool(enp101s0f0) stat: 42644155 ( 42,644,155) <= port.rx_size_64 /sec
>>>> Ethtool(enp101s0f0) stat: 42644140 ( 42,644,140) <= port.rx_unicast /sec
>>>> Ethtool(enp101s0f0) stat: 1062159456 ( 1,062,159,456) <= rx-0.bytes /sec
>>>> Ethtool(enp101s0f0) stat: 17702658 ( 17,702,658) <= rx-0.packets /sec
>>>> Ethtool(enp101s0f0) stat: 1062155639 ( 1,062,155,639) <= rx_bytes /sec
>>>> Ethtool(enp101s0f0) stat: 17756128 ( 17,756,128) <= rx_dropped /sec
>>>> Ethtool(enp101s0f0) stat: 17702594 ( 17,702,594) <= rx_packets /sec
>>>> Ethtool(enp101s0f0) stat: 35458743 ( 35,458,743) <= rx_unicast /sec
>>>>
>>>> ---
>>>>
>>>>
>>>> 4 FLOWS:
>>>>
>>>> Show adapter(s) (enp101s0f0) statistics (ONLY that changed!)
>>>> Ethtool(enp101s0f0) stat: 9351001 ( 9,351,001) <= port.fdir_sb_match /sec
>>>> Ethtool(enp101s0f0) stat: 2559136358 ( 2,559,136,358) <= port.rx_bytes /sec
>>>> Ethtool(enp101s0f0) stat: 30635346 ( 30,635,346) <= port.rx_dropped /sec
>>>> Ethtool(enp101s0f0) stat: 39986386 ( 39,986,386) <= port.rx_size_64 /sec
>>>> Ethtool(enp101s0f0) stat: 39986799 ( 39,986,799) <= port.rx_unicast /sec
>>>> Ethtool(enp101s0f0) stat: 140177834 ( 140,177,834) <= rx-0.bytes /sec
>>>> Ethtool(enp101s0f0) stat: 2336297 ( 2,336,297) <= rx-0.packets /sec
>>>> Ethtool(enp101s0f0) stat: 140260002 ( 140,260,002) <= rx-1.bytes /sec
>>>> Ethtool(enp101s0f0) stat: 2337667 ( 2,337,667) <= rx-1.packets /sec
>>>> Ethtool(enp101s0f0) stat: 140261431 ( 140,261,431) <= rx-2.bytes /sec
>>>> Ethtool(enp101s0f0) stat: 2337691 ( 2,337,691) <= rx-2.packets /sec
>>>> Ethtool(enp101s0f0) stat: 140175690 ( 140,175,690) <= rx-3.bytes /sec
>>>> Ethtool(enp101s0f0) stat: 2336262 ( 2,336,262) <= rx-3.packets /sec
>>>> Ethtool(enp101s0f0) stat: 560877338 ( 560,877,338) <= rx_bytes /sec
>>>> Ethtool(enp101s0f0) stat: 3354 ( 3,354) <= rx_dropped /sec
>>>> Ethtool(enp101s0f0) stat: 9347956 ( 9,347,956) <= rx_packets /sec
>>>> Ethtool(enp101s0f0) stat: 9351183 ( 9,351,183) <= rx_unicast /sec
>>>>
>>>>
>>>> So if I understand the field port.rx_dropped represents packets dropped
>>>> due to a lack of buffer on the NIC while rx_dropped represents packets
>>>> dropped because upper layers aren't able to process them, am I right?
>>>>
>>>> It seems that the problem is in the NIC.
>>> Yes, it seems that the problem is in the NIC hardware, or config of the
>>> NIC hardware.
>>>
>>> Look at the counter "port.fdir_sb_match":
>>> - 1 flow: 35,458,700 = port.fdir_sb_match /sec
>>> - 4 flow: 9,351,001 = port.fdir_sb_match /sec
>>>
>>> I think fdir_sb translates to Flow Director Sideband filter (in the
>>> driver code this is sometimes related to "ATR" (Application Targeted
>>> Routing)). (note: I've seen fdir_match before, but not the "sb"
>>> fdir_sb_match part). This is happening inside the NIC HW/FW that does
>>> filtering on flows and make sure same-flow goes to same RX-queue number
>>> to avoid OOO packets. This looks like the limiting factor in your setup.
>>>
>>> Have you installed any filters yourself?
>>>
>>> Try to disable Flow Director:
>>>
>>> ethtool -K ethX ntuple <on|off>
>>>
>> Yes, I'm using flow filters to manually steer traffic to different
>> queues/cores, however disabling ntuple doesn't solve the problem, the
>> port.fdir_sb_match value disappears but the number of packets dropped in
>> port.rx_dropped stays high.
>
> Try to disable your flow filters. There are indications that hardware
> cannot run these filters at these speeds.
There are no changes with flow filters disabled or enabled, except for
the presence of the port.fdir_sb_match counter, here are the results of
ethtool for 4 flows:
FLOW FILTERS DISABLED:
Show adapter(s) (enp101s0f0) statistics (ONLY that changed!)
Ethtool(enp101s0f0) stat: 2575765457 ( 2,575,765,457) <=
port.rx_bytes /sec
Ethtool(enp101s0f0) stat: 30718177 ( 30,718,177) <=
port.rx_dropped /sec
Ethtool(enp101s0f0) stat: 40246552 ( 40,246,552) <=
port.rx_size_64 /sec
Ethtool(enp101s0f0) stat: 40246558 ( 40,246,558) <=
port.rx_unicast /sec
Ethtool(enp101s0f0) stat: 143008276 ( 143,008,276) <= rx-10.bytes /sec
Ethtool(enp101s0f0) stat: 2383471 ( 2,383,471) <=
rx-10.packets /sec
Ethtool(enp101s0f0) stat: 142866811 ( 142,866,811) <= rx-13.bytes /sec
Ethtool(enp101s0f0) stat: 2381114 ( 2,381,114) <=
rx-13.packets /sec
Ethtool(enp101s0f0) stat: 142924921 ( 142,924,921) <= rx-3.bytes /sec
Ethtool(enp101s0f0) stat: 2382082 ( 2,382,082) <= rx-3.packets
/sec
Ethtool(enp101s0f0) stat: 142918015 ( 142,918,015) <= rx-6.bytes /sec
Ethtool(enp101s0f0) stat: 2381967 ( 2,381,967) <= rx-6.packets
/sec
Ethtool(enp101s0f0) stat: 571723262 ( 571,723,262) <= rx_bytes /sec
Ethtool(enp101s0f0) stat: 9528721 ( 9,528,721) <= rx_packets /sec
Ethtool(enp101s0f0) stat: 9528674 ( 9,528,674) <= rx_unicast /sec
FLOW FILTERS ENABLED:
Show adapter(s) (enp101s0f0) statistics (ONLY that changed!)
Ethtool(enp101s0f0) stat: 15810008 ( 15,810,008) <=
port.fdir_sb_match /sec
Ethtool(enp101s0f0) stat: 2634909056 ( 2,634,909,056) <=
port.rx_bytes /sec
Ethtool(enp101s0f0) stat: 31640574 ( 31,640,574) <=
port.rx_dropped /sec
Ethtool(enp101s0f0) stat: 41170436 ( 41,170,436) <=
port.rx_size_64 /sec
Ethtool(enp101s0f0) stat: 41170327 ( 41,170,327) <=
port.rx_unicast /sec
Ethtool(enp101s0f0) stat: 143016759 ( 143,016,759) <= rx-0.bytes /sec
Ethtool(enp101s0f0) stat: 2383613 ( 2,383,613) <= rx-0.packets
/sec
Ethtool(enp101s0f0) stat: 142921054 ( 142,921,054) <= rx-1.bytes /sec
Ethtool(enp101s0f0) stat: 2382018 ( 2,382,018) <= rx-1.packets
/sec
Ethtool(enp101s0f0) stat: 142943103 ( 142,943,103) <= rx-2.bytes /sec
Ethtool(enp101s0f0) stat: 2382385 ( 2,382,385) <= rx-2.packets
/sec
Ethtool(enp101s0f0) stat: 142907586 ( 142,907,586) <= rx-3.bytes /sec
Ethtool(enp101s0f0) stat: 2381793 ( 2,381,793) <= rx-3.packets
/sec
Ethtool(enp101s0f0) stat: 571775035 ( 571,775,035) <= rx_bytes /sec
Ethtool(enp101s0f0) stat: 9529584 ( 9,529,584) <= rx_packets /sec
Ethtool(enp101s0f0) stat: 9529673 ( 9,529,673) <= rx_unicast /sec
>> The only solution I've found so far is to reduce the size of the rx ring
>> as I mentioned in my former post. However I still see a decrease in
>> performance when exceeding 4 cores.
>
> What is happening when you are reducing the size of the rx ring is two
> things. (1) i40e driver have reuse/recycle-pages trick that get less
> efficient, but because you are dropping packets early you are not
> affected. (2) the total size of L3 memory you need to touch is also
> decreased.
>
> I think you are hitting case (2). The Intel CPU have a cool feature
> called DDIO (Data-Direct IO) or DCA (Direct Cache Access), which can
> deliver packet data into L3 cache memory (if NIC is directly PCIe
> connected to CPU). The CPU is in charge when this feature is enabled,
> and it will try to avoid L3 trashing and disable it in certain cases.
> When you reduce the size of the rx rings, then you are also needing
> less L3 cache memory, to the CPU will allow this DDIO feature.
>
> You can use the 'perf stat' tool to check if this is happening, by
> monitoring L3 (and L2) cache usage.
What events should I monitor? LLC-load-misses/LLC-loads?
Federico
next prev parent reply other threads:[~2020-10-15 12:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-13 13:49 Multi-core scalability problems Federico Parola
2020-10-13 16:41 ` Jesper Dangaard Brouer
2020-10-13 16:44 ` Toke Høiland-Jørgensen
2020-10-14 6:56 ` Federico Parola
2020-10-14 9:15 ` Jesper Dangaard Brouer
2020-10-14 12:17 ` Federico Parola
2020-10-14 14:26 ` Jesper Dangaard Brouer
2020-10-15 12:04 ` Federico Parola [this message]
2020-10-15 13:22 ` Jesper Dangaard Brouer
2020-10-19 15:23 ` Federico Parola
2020-10-19 18:26 ` Jesper Dangaard Brouer
2020-10-24 13:57 ` Federico Parola
2020-10-26 8:14 ` Jesper Dangaard Brouer
[not found] <VI1PR04MB3104C1D86BDC113F4AC0CF4A9E050@VI1PR04MB3104.eurprd04.prod.outlook.com>
2020-10-14 8:35 ` Federico Parola
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