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FreeBSD forwarding Performance

There are lot's of guide about tuning FreeBSD TCP performance (where the FreeBSD host is an end-point of the TCP session), but it's not the same that tunig forwarding performance (where the FreeBSD host don't have to read the TCP information of the packet being forwarded) or firewalling performance.

Concepts

How to bench a router

Definition

Clear definition regarding some relations between the bandwidth and frame rate is mandatory:

Benchmarks

Cisco or Linux

FreeBSD

Here are some benchs regarding network forwarding performance of FreeBSD (made by BSDRP team):

Bench lab

The bench lab should permit to measure the pps. For obtaining accurate result the RFC 2544 (Benchmarking Methodology for Network Interconnect Devices) is a good reference. If switches are used, they need to have proper configuration too, refers to the BSDRP performance lab for some examples.

Tuning

Literature

Here is a list of sources about optimizing/analysis forwarding performance under FreeBSD.

How to bench or tune the network stack:

FreeBSD Experimental high-performance network stacks:

Multiple flows

Don't try to bench a router with only one flow (same source|destination address and same source|destination port): You need to generate multiples flows. Multi-queue NIC uses feature like Toeplitz Hash Algorithm that balance multiples flows between all cores. Then generating only one flow will use only one NIC queue.

During your load, check that each queues are used with sysctl or with python script like this one that will display real-time usage of each queue.

On this example we can see that all flows are correctly shared between each 8 queues (about 340K paquets-per-seconds for each):

[root@router]~# nic-queue-usage cxl0
[Q0   346K/s] [Q1   343K/s] [Q2   339K/s] [Q3   338K/s] [Q4   338K/s] [Q5   338K/s] [Q6   343K/s] [Q7   346K/s] [QT  2734K/s  3269K/s ->     0K/s]
[Q0   347K/s] [Q1   344K/s] [Q2   339K/s] [Q3   339K/s] [Q4   338K/s] [Q5   338K/s] [Q6   343K/s] [Q7   346K/s] [QT  2735K/s  3277K/s ->     0K/s]
[Q0   344K/s] [Q1   341K/s] [Q2   338K/s] [Q3   338K/s] [Q4   337K/s] [Q5   337K/s] [Q6   342K/s] [Q7   345K/s] [QT  2727K/s  3262K/s ->     0K/s]
[Q0   355K/s] [Q1   352K/s] [Q2   348K/s] [Q3   349K/s] [Q4   348K/s] [Q5   347K/s] [Q6   352K/s] [Q7   355K/s] [QT  2809K/s  3381K/s ->     0K/s]
[Q0   351K/s] [Q1   348K/s] [Q2   344K/s] [Q3   343K/s] [Q4   342K/s] [Q5   344K/s] [Q6   349K/s] [Q7   352K/s] [QT  2776K/s  3288K/s ->     0K/s]
[Q0   344K/s] [Q1   341K/s] [Q2   338K/s] [Q3   339K/s] [Q4   338K/s] [Q5   338K/s] [Q6   343K/s] [Q7   346K/s] [QT  2731K/s  3261K/s ->     0K/s]
Beware of configurations setup that prevent multi-queue, like GRE,GIF,IPSec tunnels or PPPoE (= same source/destination address). If PPPoE usage is mandatory on your Gigabit Internet link, using small hardware, like 4 cores AMD GX (PC Engines APU2), will prevent to reach Gigabit speed.

Choosing hardware

CPU

Avoid NUMA architecture but prefer a CPU in only one package with maximum core (8 or 16). If you are using NUMA, you need to check that inbound/outbound NIC queues are correctly bind to their local package to avoid useless QPI crossing.

Network Interface Card

Mellanox or Chelsio, by mixing good chipset and excellent drivers are an excellent choice.

Intel seems to have problem for managing lot's of PPS (= IRQ).

Avoid “embedded” NIC into common Dell/HP servers like these one that are very bad regarding their maximum packets-per-second performance:

  • 10G Emulex OneConnect (be3)
  • 10G Broadcom NetXtreme II BCM57810

Choosing good FreeBSD release

Before tuning, you need to use the good FreeBSD version… this mean a recent FreeBSD -head.

BSDRP is currently following FreeBSD 12-stable branch, to try to have a mix between recent features and stability.

Disabling Hyper Threading (on specific CPU only)

By default a multi-queue NIC drivers create one queue per core. But on some older CPU (like Xeon E5-2650 V1) those logical cores didn't help at all for managing interrupts generated by high speed NIC.

HT can be disabled with this command:

echo 'machdep.hyperthreading_allowed="0"' >> /boot/loader.conf

Here is an example on a Xeon E5 2650 (8c,16t) and 10G Chelsio NIC where it improve performance by disabling HT:

x HT-enabled-8rxq(default): inet packets-per-second forwarded
+ HT-enabled-16rxq: inet packets-per-second forwarded
* HT-disabled-8rxq: inet packets-per-seconds forwarded
+--------------------------------------------------------------------------+
|                                                                        **|
|x      xx    x          +       + + +  +                               ***|
|   |____A_____|                                                           |
|                           |_____AM____|                                  |
|                                                                       |A||
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5       4500078       4735822       4648451     4648293.8     94545.404
+   5       4925106       5198632       5104512     5088362.1     102920.87
Difference at 95.0% confidence
        440068 +/- 144126
        9.46731% +/- 3.23827%
        (Student's t, pooled s = 98821.9)
*   5       5765684     5801231.5       5783115     5785004.7     13724.265
Difference at 95.0% confidence
        1.13671e+06 +/- 98524.2
        24.4544% +/- 2.62824%
        (Student's t, pooled s = 67554.4)

There is a benefit of about 24% to disable hyper threading on this old CPU.

But here is another example where there is a benefit to kept it enabled (and with the NIC configured to uses all the treads) on Xeon E5 2650L (10c, 20t):

x HT on, 8q (default): inet4 packets-per-second forwarded
+ HT off, 8q: inet4 packets-per-second forwarded
* HT on, 16q: inet4 packets-per-second forwarded
+--------------------------------------------------------------------------+
|x x              ++                                                   *  *|
|x xx            +++                                                 * *  *|
||AM|            |A_|                                                |_MA_||
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5       4265579     4433699.5     4409249.5     4359580.3       81559.4
+   5       5257621       5443012       5372493     5372693.5     73316.243
Difference at 95.0% confidence
        1.01311e+06 +/- 113098
        23.2388% +/- 2.94299%
        (Student's t, pooled s = 77547.4)
*   5       8566972       8917315     8734750.5     8769616.1     147186.74
Difference at 95.0% confidence
        4.41004e+06 +/- 173536
        101.157% +/- 5.21388%
        (Student's t, pooled s = 118987)

fastforwarding

FreeBSD 10.3 or older

You should enable fastforwarding with a:

echo "net.inet.ip.fastforwarding=1" >> /etc/sysctl.conf
service sysctl restart

FreeBSD 12.0 or newer

You should enable tryforward by disabling ICMP redirect:

echo "net.inet.ip.redirect=0"  >> /etc/sysctl.conf
echo "net.inet6.ip6.redirect=0" >> /etc/sysctl.conf
service sysctl restart

Entropy harvest impact

Lot's of tuning guide indicate to disable:

  • kern.random.sys.harvest.ethernet
  • kern.random.sys.harvest.interrupt

By default the binary mask 511 select almost all these source as entropy sources:

kern.random.harvest.mask_symbolic: [UMA],[FS_ATIME],SWI,INTERRUPT,NET_NG,NET_ETHER,NET_TUN,MOUSE,KEYBOARD,ATTACH,CACHED
kern.random.harvest.mask_bin: 00111111111
kern.random.harvest.mask: 511

By replacing this mask by 351, we exclude INTERRUPT and NET_ETHER:

kern.random.harvest.mask_symbolic: [UMA],[FS_ATIME],SWI,[INTERRUPT],NET_NG,[NET_ETHER],NET_TUN,MOUSE,KEYBOARD,ATTACH,CACHED
kern.random.harvest.mask_bin: 00101011111
kern.random.harvest.mask: 351

And we can notice on forwarding performance of a FreeBSD 11.1:

x PC-Engines-APU2-igb, 511 (default): inet4 packets-per-second
+ PC-Engines-APU2-igb, 351: inet4 packets-per-second
+--------------------------------------------------------------------------+
|xx  x       xx                                 +      +    +    +        +|
||___M_A_____|                                                             |
|                                                  |________A_________|    |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5        724811        730197        726304      727281.6     2522.9161
+   5        744832      755871.5        749956      750112.9     4208.7383
Difference at 95.0% confidence
        22831.3 +/- 5060.46
        3.13927% +/- 0.701645%
        (Student's t, pooled s = 3469.77

On a PC Engines APU2, there is +3% performance benefit

x Netgate-igb, 511 (default): inet4 packets-per-second
+ Netgate-igb, 351: inet4 packets-per-second
+--------------------------------------------------------------------------+
|x x    x          x     x                                   ++      +  + +|
||______M__A__________|                                                    |
|                                                             |_____AM___| |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5      946426.5        965962        951906      954721.7     8435.4561
+   5        994839       1005327       1000935     1000098.2     4620.4263
Difference at 95.0% confidence
        45376.5 +/- 9918.76
        4.75285% +/- 1.0771%
        (Student's t, pooled s = 6800.93)

On a Netgate RCC-VE 4860 there is about 4.7% performance benefit.

Using the FreeBSD “projects/routing” branch, this impact is a lot's more important:

Impact of disabling some entropy source on FreeBSD forwarding performance

NIC drivers tuning

RX & TX descriptor (queue) size on igb

Received (hw.igb.rxd) and transmit (hw.igb.txd) internal buffer size of igb/em NIC can be increased, but it's not a good idea.

Here are some examples that decrease performance when buffer increased:

x PC-Engine-APU2-igb, 1024 (default): inet4 packets-per-second
+ PC-Engine-APU2-igb, 2048: inet4 packets-per-second
* PC-Engine-APU2-igb, 4096: inet4 packets-per-second
+--------------------------------------------------------------------------+
|*                                                                         |
|* ***                  + +  +++                                      xx xx|
|                                                                      MA| |
|                        |__AM_|                                           |
||_A_|                                                                     |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5        724024        731531        726058      727317.6     3006.2996
+   5        626546        640326        637463      634497.6     5856.2198
Difference at 95.0% confidence
        -92820 +/- 6788.67
        -12.762% +/- 0.909828%
        (Student's t, pooled s = 4654.74)
*   5        577830        585426        582886      581913.4     3413.6019
Difference at 95.0% confidence
        -145404 +/- 4690.94
        -19.9918% +/- 0.592106%
        (Student's t, pooled s = 3216.4)

On a PC Engines APU2, increasing rx&tx buffers badly impact forwarding perfomance to about 20%.

x Netgate-igb, 1024 (default): inet4 packets-per-second
+ Netgate-igb, 2048: inet4 packets-per-second
* Netaget-igb, 4096: inet4 packets-per-second
+--------------------------------------------------------------------------+
|*      *       *    *   *+   ++      +    +               x   x x      x x|
|                                                           |____MA______| |
|                          |___M__A______|                                 |
|   |_________A_M______|                                                   |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5        943843        961431        950960      952699.4     7285.7808
+   5        907050        926520        912317      915489.3       7816.85
Difference at 95.0% confidence
        -37210.1 +/- 11020
        -3.90575% +/- 1.13593%
        (Student's t, pooled s = 7555.98)
*   5        877923        904869        894519      892616.2     10954.317
Difference at 95.0% confidence
        -60083.2 +/- 13567.4
        -6.30663% +/- 1.39717%
        (Student's t, pooled s = 9302.68)

On a Netgate RCC-VE 4860 performance decrease to about 6%.

Maximum number of received packets to process at a time (Intel)

By default Intel drivers (em|igb) limit the maximum number of received packets to process at a time (hw.igb.rx_process_limit=100).

Disabling this limit can improve a little bit the overall performance:

x PC-Engines-APU2-igb, 100 (default): inet4 packets-per-second
+ PC-Engines-APU2-igb, disabled: inet4 packets-per-second
+--------------------------------------------------------------------------+
|x         x                   x   x     x               +        ++ +    +|
|      |________________A______M_________|                                 |
|                                                            |_____A_____| |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5        721322        729817        727669      726175.8     3592.7624
+   5        733327        736835        735392      735283.4     1266.5036
Difference at 95.0% confidence
        9107.6 +/- 3928.6
        1.25419% +/- 0.547037%
        (Student's t, pooled s = 2693.69)

A small 1% improvement on a PC Engines APU2.

x Netgate-igb, 100 (default): inet4 packets-per-second
+ Netgate-igb, disabled: inet4 packets-per-second
+--------------------------------------------------------------------------+
|x    x         x                    x              x  +    + +        +  +|
||______________M_____A_____________________|                              |
|                                                       |_____M_A_______|  |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5        943049        963053        948889      951350.1     8428.1046
+   5        964038        971603        966764      967747.4     3168.1615
Difference at 95.0% confidence
        16397.3 +/- 9285.49
        1.72358% +/- 0.990789%
        (Student's t, pooled s = 6366.72)

Almost same improvement, 1.7% on a Netgate.

Increasing maximum interrupts per second

By default igb|em limit the maximum number of interrupts per second to 8000.

What result by increasing this number:

x PC-Engine-APU2-igb, max_interrupt_rate=8000 (default): inet4 pps
+ PC-Engine-APU2-igb, max_interrupt_rate=16000: inet4 pps
* PC-Engine-APU2-igb, max_interrupt_rate=32000: inet4 pps
+--------------------------------------------------------------------------+
|x           x              +   x*     *+*              *  x+x           +*|
|     |_________________________MA__________________________|              |
|                         |_____________M_____A___________________|        |
|                                |_______M_______A_______________|         |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5        721191        730448        725919      726128.6     4137.1981
+   5        725281        732247        727142        728045     3083.0635
No difference proven at 95.0% confidence
*   5        726157        732417        727400        728554     2518.7778
No difference proven at 95.0% confidence

No benefit on a PC Engines APU2.

x Netgate-igb, max_interrupt_rate=8000 (default): inet4 pps
+ Netgate-igb, max_interrupt_rate=16000: inet4 pps
* Netgate-igb, max_interrupt_rate=32000: inet4 pps
+--------------------------------------------------------------------------+
|x              *   x    x*   +*   x       +       *       +   +    *     +|
|       |________________MA__________________|                             |
|                                    |________________A____M___________|   |
|                |_____________M_______A____________________|              |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5      936969.5        954851        945631      946049.3      6595.479
+   5        947461        962965        957754        955782      6143.043
Difference at 95.0% confidence
        9732.7 +/- 9295.06
        1.02877% +/- 0.987938%
        (Student's t, pooled s = 6373.28)
*   5        942302        960913        947667      950327.4     7504.7836
No difference proven at 95.0% confidence

A little 1% benefit if doubled form the default (8000 to 16000), but no benefit after.

Disabling LRO and TSO

All modern NIC support LRO and TSO features that needs to be disabled on a router:

  1. By waiting to store multiple packets at the NIC level before to hand them up to the stack: This add latency, and because all packets need to be sending out again, the stack have to split in different packets again before to hand them down to the NIC. Intel drivers readme include this note “The result of not disabling LRO when combined with ip forwarding or bridging can be low throughput or even a kernel panic.”
  2. This break the End-to-end principle

There is no real impact of disabling these features on PPS performance:

x Xeon_E5-2650-8Cores-Chelsio_T540, TSO-LRO-enabled (default): inet4 packets-per-second
+ Xeon_E5-2650-8Cores-Chelsio_T540, TSO-LRO-disabled: inet4 packets-per-second
+--------------------------------------------------------------------------+
|x                    x     +x        +     x  +x                   +     +|
|         |__________________A__________________|                          |
|                              |_______________M___A__________________|    |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5       5727360     5806270.5       5773573     5773454.5     31394.005
+   5       5771681       5848728       5803277     5810232.2     32556.338
No difference proven at 95.0% confidence

Where is the bottleneck ?

Tools:

Packets load

Display the information regarding packet traffic, with refresh each second.

Here is a first example:

[root@hp]~# netstat -ihw1
            input        (Total)           output
   packets  errs idrops      bytes    packets  errs      bytes colls
       14M     0  7.9M       836M       5.8M     0       353M     0
       14M     0  8.0M       841M       5.8M     0       352M     0
       14M     0  8.1M       849M       5.8M     0       353M     0
       14M     0  7.8M       833M       5.8M     0       352M     0
       14M     0  7.9M       837M       5.8M     0       352M     0
       14M     0  8.0M       843M       5.8M     0       353M     0
       14M     0  7.9M       838M       5.8M     0       352M     0

⇒ This system is receiving 14Mpps (10G line-rate) and reach to forwarding only at 5.8Mpps rate then need to drop about 8Mpps.

Traffic distribution between each queues

Check the input queues are equally distributed. BSDRP include a sysctl parser script for that:

[root@hp]~# nic-queue-usage cxl0
[Q0   935K/s] [Q1   944K/s] [Q2   925K/s] [Q3   912K/s] [Q4   914K/s] [Q5   914K/s] [Q6   930K/s] [Q7   922K/s] [QT  7400K/s 17749K/s ->     2K/s]
[Q0   886K/s] [Q1   892K/s] [Q2   872K/s] [Q3   883K/s] [Q4   885K/s] [Q5   885K/s] [Q6   906K/s] [Q7   900K/s] [QT  7112K/s 16950K/s ->     1K/s]
[Q0   874K/s] [Q1   879K/s] [Q2   855K/s] [Q3   855K/s] [Q4   852K/s] [Q5   842K/s] [Q6   866K/s] [Q7   860K/s] [QT  6887K/s 16748K/s ->     1K/s]
[Q0   892K/s] [Q1   899K/s] [Q2   870K/s] [Q3   865K/s] [Q4   873K/s] [Q5   882K/s] [Q6   899K/s] [Q7   893K/s] [QT  7076K/s 17023K/s ->     1K/s]
[Q0   880K/s] [Q1   890K/s] [Q2   878K/s] [Q3   882K/s] [Q4   883K/s] [Q5   885K/s] [Q6   904K/s] [Q7   896K/s] [QT  7102K/s 16864K/s ->     1K/s]
[Q0   894K/s] [Q1   891K/s] [Q2   868K/s] [Q3   864K/s] [Q4   860K/s] [Q5   860K/s] [Q6   882K/s] [Q7   873K/s] [QT  6996K/s 17154K/s ->     1K/s]
[Q0   876K/s] [Q1   889K/s] [Q2   873K/s] [Q3   876K/s] [Q4   881K/s] [Q5   878K/s] [Q6   898K/s] [Q7   890K/s] [QT  7064K/s 16586K/s ->     1K/s]
[Q0   957K/s] [Q1   964K/s] [Q2   941K/s] [Q3   941K/s] [Q4   943K/s] [Q5   945K/s] [Q6   967K/s] [Q7   963K/s] [QT  7624K/s 18220K/s ->     1K/s]
[Q0   864K/s] [Q1   873K/s] [Q2   853K/s] [Q3   852K/s] [Q4   854K/s] [Q5   856K/s] [Q6   874K/s] [Q7   868K/s] [QT  6897K/s 16413K/s ->     1K/s]

⇒ All 8 receive queues are correctly used here.

Interrupt usage

Report on the number of interrupts taken by each device since system startup,

Here is a first example:

[root@hp]~# vmstat -i
interrupt                          total       rate
irq1: atkbd0                           6          0
irq4: uart0                            3          0
irq20: ehci1                        3263          3
irq21: ehci0                       12612         10
cpu0:timer                        749022        583
cpu6:timer                        736682        573
cpu7:timer                        742555        578
cpu1:timer                        739964        576
cpu2:timer                        739621        575
cpu5:timer                        738796        575
cpu4:timer                        738756        575
cpu3:timer                        737954        574
irq273: igb1:que 0                  1291          1
irq274: igb1:que 1                  1245          1
irq275: igb1:que 2                  1245          1
irq276: igb1:que 3                  1246          1
irq277: igb1:que 4                  1245          1
irq278: igb1:que 5                  2435          2
irq279: igb1:que 6                  1245          1
irq280: igb1:que 7                  1245          1
irq281: igb1:link                      2          0
irq283: t5nex0:evt                     4          0
irq284: t5nex0:0a0                608689        474
irq285: t5nex0:0a1                281882        219
irq286: t5nex0:0a2                875179        681
irq287: t5nex0:0a3                813033        632
irq288: t5nex0:0a4                968845        754
irq289: t5nex0:0a5               1099491        855
irq290: t5nex0:0a6                 58210         45
irq291: t5nex0:0a7                638755        497
irq294: t5nex0:1a0                102669         80
irq295: t5nex0:1a1                136891        106
irq296: t5nex0:1a2                 51888         40
irq297: t5nex0:1a3                 59324         46
irq298: t5nex0:1a4                 61052         47
irq299: t5nex0:1a5                 80827         63
irq300: t5nex0:1a6                 88800         69
irq301: t5nex0:1a7                102177         79
Total                           11978149       9318

⇒ There is no IRQ sharing here, and each queue have correctly their own IRQ (thanks MSI-X).

Memory Buffer

Show statistics recorded by the memory management routines. The network manages a private pool of memory buffers.

[root@hp]~# vmstat -z | head -1 ; vmstat -z | grep -i mbuf
ITEM                   SIZE  LIMIT     USED     FREE      REQ FAIL SLEEP
mbuf_packet:            256, 26137965,    8190,    1424,    9121,   0,   0
mbuf:                   256, 26137965,    3657,    4699,4372990387,   0,   0
mbuf_cluster:          2048, 4084056,    9614,      12,    9614,   0,   0
mbuf_jumbo_page:       4096, 2042027,   16192,     131,   16207,   0,   0
mbuf_jumbo_9k:         9216, 605045,       0,       0,       0,   0,   0
mbuf_jumbo_16k:       16384, 340337,     128,       0,     128,   0,   0

⇒ No “failed” here.

CPU / NIC

top can give very useful information regarding the CPU/NIC affinity:

[root@hp]~# top -CHIPS
last pid:  1180;  load averages: 10.05,  8.86,  5.71                                                 up 0+00:23:58  12:05:19
187 processes: 15 running, 100 sleeping, 72 waiting
CPU 0:  0.0% user,  0.0% nice,  0.0% system, 96.9% interrupt,  3.1% idle
CPU 1:  0.0% user,  0.0% nice,  0.0% system, 99.2% interrupt,  0.8% idle
CPU 2:  0.0% user,  0.0% nice,  0.0% system, 99.6% interrupt,  0.4% idle
CPU 3:  0.0% user,  0.0% nice,  0.0% system, 97.7% interrupt,  2.3% idle
CPU 4:  0.0% user,  0.0% nice,  0.0% system, 98.1% interrupt,  1.9% idle
CPU 5:  0.0% user,  0.0% nice,  0.0% system, 97.3% interrupt,  2.7% idle
CPU 6:  0.0% user,  0.0% nice,  0.0% system, 97.7% interrupt,  2.3% idle
CPU 7:  0.0% user,  0.0% nice,  0.0% system, 97.3% interrupt,  2.7% idle
Mem: 16M Active, 16M Inact, 415M Wired, 7239K Buf, 62G Free
Swap:

  PID USERNAME   PRI NICE   SIZE    RES STATE   C   TIME     CPU COMMAND
   12 root       -92    -     0K  1248K CPU1    1  13:14 100.00% intr{irq285: t5nex0:0a1}
   12 root       -92    -     0K  1248K CPU7    7  13:09  98.54% intr{irq284: t5nex0:0a0}
   12 root       -92    -     0K  1248K WAIT    3  13:10  98.21% intr{irq291: t5nex0:0a7}
   12 root       -92    -     0K  1248K WAIT    6  13:02  97.33% intr{irq287: t5nex0:0a3}
   12 root       -92    -     0K  1248K CPU0    0  13:02  97.30% intr{irq286: t5nex0:0a2}
   12 root       -92    -     0K  1248K CPU5    5  13:01  97.26% intr{irq288: t5nex0:0a4}
   12 root       -92    -     0K  1248K WAIT    4  12:59  97.19% intr{irq289: t5nex0:0a5}
   12 root       -92    -     0K  1248K CPU2    2  13:17  11.43% intr{irq290: t5nex0:0a6}
   11 root       155 ki31     0K   128K RUN     5  11:02   2.86% idle{idle: cpu5}
   11 root       155 ki31     0K   128K RUN     6  10:58   2.31% idle{idle: cpu6}
   11 root       155 ki31     0K   128K RUN     3  10:52   2.11% idle{idle: cpu3}
   11 root       155 ki31     0K   128K CPU4    4  10:58   2.05% idle{idle: cpu4}
   11 root       155 ki31     0K   128K RUN     7  10:54   1.87% idle{idle: cpu7}
   11 root       155 ki31     0K   128K RUN     0  10:54   1.72% idle{idle: cpu0}
   11 root       155 ki31     0K   128K RUN     1  10:52   1.20% idle{idle: cpu1}
   15 root       -16    -     0K    16K -       7   0:02   0.24% rand_harvestq
    0 root       -92    -     0K   624K -       6   0:01   0.10% kernel{t5nex0 tq1}
   11 root       155 ki31     0K   128K RUN     2  10:44   0.09% idle{idle: cpu2}
 1180 root        20    0 20012K  3876K CPU4    4   0:00   0.06% top
   12 root       -92    -     0K  1248K WAIT    0   0:00   0.04% intr{irq301: t5nex0:1a7}
   12 root       -92    -     0K  1248K WAIT    6   0:00   0.03% intr{irq295: t5nex0:1a1}
   12 root       -92    -     0K  1248K WAIT    4   0:00   0.03% intr{irq300: t5nex0:1a6}
   12 root       -92    -     0K  1248K WAIT    7   0:00   0.03% intr{irq299: t5nex0:1a5}
   12 root       -92    -     0K  1248K WAIT    0   0:00   0.03% intr{irq294: t5nex0:1a0}
   12 root       -60    -     0K  1248K WAIT    1   0:00   0.02% intr{swi4: clock (0)}
   12 root       -92    -     0K  1248K WAIT    4   0:00   0.02% intr{irq296: t5nex0:1a2}
   12 root       -92    -     0K  1248K WAIT    0   0:00   0.02% intr{irq298: t5nex0:1a4}
   12 root       -92    -     0K  1248K WAIT    0   0:00   0.01% intr{irq297: t5nex0:1a3}
 1090 root        20    0 56296K  6384K select  3   0:00   0.00% sshd
   14 root       -68    -     0K   240K -       6   0:00   0.00% usb{usbus2}
   14 root       -68    -     0K   240K -       6   0:00   0.00% usb{usbus2}
   14 root       -68    -     0K   240K -       6   0:00   0.00% usb{usbus0}
   12 root       -88    -     0K  1248K WAIT    6   0:00   0.00% intr{irq20: ehci1}
   12 root       -92    -     0K  1248K WAIT    5   0:00   0.00% intr{irq278: igb1:que 5}
   14 root       -68    -     0K   240K -       6   0:00   0.00% usb{usbus0}
   12 root       -88    -     0K  1248K WAIT    6   0:00   0.00% intr{irq21: ehci0}
   14 root       -68    -     0K   240K -       1   0:00   0.00% usb{usbus1}
   18 root       -16    -     0K    48K psleep  5   0:00   0.00% pagedaemon{pagedaemon}
   24 root        16    -     0K    16K syncer  0   0:00   0.00% syncer
   21 root       -16    -     0K    16K -       5   0:00   0.00% bufspacedaemon
   23 root       -16    -     0K    16K vlruwt  7   0:00   0.00% vnlru

Drivers

Depending the NIC drivers used, there are some counters available:

[root@hp]~# sysctl dev.cxl.0.stats.
dev.cxl.0.stats.rx_ovflow2: 0
dev.cxl.0.stats.rx_ovflow1: 0
dev.cxl.0.stats.rx_ovflow0: 7301719197
dev.cxl.0.stats.rx_ppp7: 0
dev.cxl.0.stats.rx_ppp6: 0
dev.cxl.0.stats.rx_ppp5: 0
dev.cxl.0.stats.rx_ppp4: 0
dev.cxl.0.stats.rx_ppp3: 0
dev.cxl.0.stats.rx_ppp2: 0
dev.cxl.0.stats.rx_ppp1: 0
dev.cxl.0.stats.rx_ppp0: 0
dev.cxl.0.stats.rx_pause: 0
dev.cxl.0.stats.rx_frames_1519_max: 0
dev.cxl.0.stats.rx_frames_1024_1518: 0
dev.cxl.0.stats.rx_frames_512_1023: 0
dev.cxl.0.stats.rx_frames_256_511: 0
dev.cxl.0.stats.rx_frames_128_255: 0
dev.cxl.0.stats.rx_frames_65_127: 0
dev.cxl.0.stats.rx_frames_64: 12522860904
(...)
[root@hp]~# sysctl -d dev.cxl.0.stats.rx_ovflow0
dev.cxl.0.stats.rx_ovflow0: # drops due to buffer-group 0 overflows

⇒ Notice the high level of “drops du to buffer-group 0 overflows”. It's a problem regarding global performance of the system (on this example, the packet generator send smallest packet at a rate about 14Mpps).

pmcstat

During high-load of your router/firewall, load the hwpmc(4) module:

kldload hwpmc
Time used by process

Now you can display the most time consumed process with:

pmcstat -TS inst_retired.any_p -w1

That will display this output:

PMC: [INSTR_RETIRED_ANY] Samples: 56877 (100.0%) , 0 unresolved

%SAMP IMAGE      FUNCTION             CALLERS
  7.2 kernel     bzero                m_pkthdr_init:2.4 ip_findroute:1.8 ip_tryforward:1.6 fib4_lookup_nh_basic:1.3
  6.1 if_cxgbe.k eth_tx               drain_ring
  5.9 kernel     bcopy                eth_tx:2.3 arpresolve:1.9 get_scatter_segment:1.7
  4.5 kernel     atomic_cmpset_long   mp_ring_enqueue:2.5 drain_ring:2.0
  3.7 kernel     __rw_rlock           arpresolve:2.7 fib4_lookup_nh_basic:1.0
  3.4 kernel     rn_match             fib4_lookup_nh_basic
  3.3 kernel     ip_tryforward        ip_input
  3.2 kernel     _rw_runlock_cookie   fib4_lookup_nh_basic:2.2 arpresolve:1.0
  2.9 if_cxgbe.k reclaim_tx_descs     eth_tx
  2.9 if_cxgbe.k service_iq           t4_intr
  2.9 kernel     ether_output         ip_tryforward
  2.8 kernel     ether_nh_input       netisr_dispatch_src
  2.8 if_cxgbe.k cxgbe_transmit       ether_output
  2.8 kernel     netisr_dispatch_src  ether_demux:1.7 ether_input:1.1
  2.7 kernel     uma_zalloc_arg       get_scatter_segment
  2.5 kernel     _rm_rlock            in_localip
  2.4 if_cxgbe.k t4_eth_rx            service_iq
  2.3 if_cxgbe.k parse_pkt            cxgbe_transmit
  2.3 kernel     memcpy               ether_output
  2.2 kernel     uma_zfree_arg        m_freem
  2.1 kernel     spinlock_exit        ether_nh_input
  2.0 kernel     fib4_lookup_nh_basic ip_findroute
  2.0 kernel     ip_input             netisr_dispatch_src
  2.0 if_cxgbe.k get_scatter_segment  service_iq
  1.9 kernel     __mtx_lock_flags     eth_tx
  1.8 kernel     __mtx_unlock_flags   eth_tx
  1.6 kernel     random_harvest_queue ether_nh_input
  1.4 if_cxgbe.k mp_ring_enqueue      cxgbe_transmit
  1.1 kernel     bcmp                 ether_nh_input
  1.1 kernel     critical_enter
  1.1 kernel     key_havesp           ipsec4_capability
  1.0 kernel     m_adj                ether_demux
  1.0 kernel     ipsec4_capability    ip_input
  1.0 kernel     in_localip           ip_tryforward
  0.9 kernel     pmap_kextract        parse_pkt
  0.7 kernel     ether_demux          ether_nh_input
  0.7 kernel     arpresolve           ether_output
  0.7 kernel     _rm_runlock          in_localip
  0.7 kernel     sglist_count         parse_pkt
  0.6 kernel     lock_delay           _mtx_lock_spin_cookie
  0.6 kernel     critical_exit

On this case the bootleneck is just the network stack (most of the time spend into function ip_findroute called by ip_tryforward).

CPU cycles spent

For displaying where the most cpu cycles are being spent with. We first need a partition with about 200MB that include the debug kernel:

system expand-data-slice
mount /data

Then, under high-load, start collecting during about 20 seconds:

pmcstat -z 50 -S cpu_clk_unhalted.thread -l 20 -O /data/pmc.out
pmcstat -R /data/pmc.out -z50 -G /data/pmc.stacks
less /data/pmc.stacks

Lock contention source

To identifying lock contention source (like if function lock_delay or __mtx_lock_sleep was quite high from the pcm output), you can try to search which lock is contended and why with lockstat.

You can generate 2 output:

  • contented locks broken down by type:
    lockstat -x aggsize=4m sleep 10 > lock-type.txt
  • stacks associated with the lock contention to identify the source:
    lockstat -x aggsize=4m -s 10 sleep 10 > lock-stacks.txt 
documentation/technical_docs/performance.txt · Last modified: 2020/01/18 01:04 by olivier