Re: [Qemu-devel] [PATCH 00/12] Multiqueue virtio-net

[Jason Wang]

On 01/10/2013 04:44 PM, Stefan Hajnoczi wrote:
> On Wed, Jan 09, 2013 at 11:33:25PM +0800, Jason Wang wrote:
>> On 01/09/2013 11:32 PM, Michael S. Tsirkin wrote:
>>> On Wed, Jan 09, 2013 at 03:29:24PM +0100, Stefan Hajnoczi wrote:
>>>> On Fri, Dec 28, 2012 at 06:31:52PM +0800, Jason Wang wrote:
>>>>> Perf Numbers:
>>>>>
>>>>> Two Intel Xeon 5620 with direct connected intel 82599EB
>>>>> Host/Guest kernel: David net tree
>>>>> vhost enabled
>>>>>
>>>>> - lots of improvents of both latency and cpu utilization in 
>>>>> request-reponse test
>>>>> - get regression of guest sending small packets which because TCP tends 
>>>>> to batch
>>>>>   less when the latency were improved
>>>>>
>>>>> 1q/2q/4q
>>>>> TCP_RR
>>>>>  size #sessions trans.rate  norm trans.rate  norm trans.rate  norm
>>>>> 1 1     9393.26   595.64  9408.18   597.34  9375.19   584.12
>>>>> 1 20    72162.1   2214.24 129880.22 2456.13 196949.81 2298.13
>>>>> 1 50    107513.38 2653.99 139721.93 2490.58 259713.82 2873.57
>>>>> 1 100   126734.63 2676.54 145553.5  2406.63 265252.68 2943
>>>>> 64 1    9453.42   632.33  9371.37   616.13  9338.19   615.97
>>>>> 64 20   70620.03  2093.68 125155.75 2409.15 191239.91 2253.32
>>>>> 64 50   106966    2448.29 146518.67 2514.47 242134.07 2720.91
>>>>> 64 100  117046.35 2394.56 190153.09 2696.82 238881.29 2704.41
>>>>> 256 1   8733.29   736.36  8701.07   680.83  8608.92   530.1
>>>>> 256 20  69279.89  2274.45 115103.07 2299.76 144555.16 1963.53
>>>>> 256 50  97676.02  2296.09 150719.57 2522.92 254510.5  3028.44
>>>>> 256 100 150221.55 2949.56 197569.3  2790.92 300695.78 3494.83
>>>>> TCP_CRR
>>>>>  size #sessions trans.rate  norm trans.rate  norm trans.rate  norm
>>>>> 1 1     2848.37  163.41 2230.39  130.89 2013.09  120.47
>>>>> 1 20    23434.5  562.11 31057.43 531.07 49488.28 564.41
>>>>> 1 50    28514.88 582.17 40494.23 605.92 60113.35 654.97
>>>>> 1 100   28827.22 584.73 48813.25 661.6  61783.62 676.56
>>>>> 64 1    2780.08  159.4  2201.07  127.96 2006.8   117.63
>>>>> 64 20   23318.51 564.47 30982.44 530.24 49734.95 566.13
>>>>> 64 50   28585.72 582.54 40576.7  610.08 60167.89 656.56
>>>>> 64 100  28747.37 584.17 49081.87 667.87 60612.94 662
>>>>> 256 1   2772.08  160.51 2231.84  131.05 2003.62  113.45
>>>>> 256 20  23086.35 559.8  30929.09 528.16 48454.9  555.22
>>>>> 256 50  28354.7  579.85 40578.31 607    60261.71 657.87
>>>>> 256 100 28844.55 585.67 48541.86 659.08 61941.07 676.72
>>>>> TCP_STREAM guest receiving
>>>>>  size #sessions throughput  norm throughput  norm throughput  norm
>>>>> 1 1     16.27   1.33   16.1    1.12   16.13   0.99
>>>>> 1 2     33.04   2.08   32.96   2.19   32.75   1.98
>>>>> 1 4     66.62   6.83   68.3    5.56   66.14   2.65
>>>>> 64 1    896.55  56.67  914.02  58.14  898.9   61.56
>>>>> 64 2    1830.46 91.02  1812.02 64.59  1835.57 66.26
>>>>> 64 4    3626.61 142.55 3636.25 100.64 3607.46 75.03
>>>>> 256 1   2619.49 131.23 2543.19 129.03 2618.69 132.39
>>>>> 256 2   5136.58 203.02 5163.31 141.11 5236.51 149.4
>>>>> 256 4   7063.99 242.83 9365.4  208.49 9421.03 159.94
>>>>> 512 1   3592.43 165.24 3603.12 167.19 3552.5  169.57
>>>>> 512 2   7042.62 246.59 7068.46 180.87 7258.52 186.3
>>>>> 512 4   6996.08 241.49 9298.34 206.12 9418.52 159.33
>>>>> 1024 1  4339.54 192.95 4370.2  191.92 4211.72 192.49
>>>>> 1024 2  7439.45 254.77 9403.99 215.24 9120.82 222.67
>>>>> 1024 4  7953.86 272.11 9403.87 208.23 9366.98 159.49
>>>>> 4096 1  7696.28 272.04 7611.41 270.38 7778.71 267.76
>>>>> 4096 2  7530.35 261.1  8905.43 246.27 8990.18 267.57
>>>>> 4096 4  7121.6  247.02 9411.75 206.71 9654.96 184.67
>>>>> 16384 1 7795.73 268.54 7780.94 267.2  7634.26 260.73
>>>>> 16384 2 7436.57 255.81 9381.86 220.85 9392    220.36
>>>>> 16384 4 7199.07 247.81 9420.96 205.87 9373.69 159.57
>>>>> TCP_MAERTS guest sending
>>>>>  size #sessions throughput  norm throughput  norm throughput  norm
>>>>> 1 1     15.94   0.62   15.55   0.61   15.13   0.59
>>>>> 1 2     36.11   0.83   32.46   0.69   32.28   0.69
>>>>> 1 4     71.59   1      68.91   0.94   61.52   0.77
>>>>> 64 1    630.71  22.52  622.11  22.35  605.09  21.84
>>>>> 64 2    1442.36 30.57  1292.15 25.82  1282.67 25.55
>>>>> 64 4    3186.79 42.59  2844.96 36.03  2529.69 30.06
>>>>> 256 1   1760.96 58.07  1738.44 57.43  1695.99 56.19
>>>>> 256 2   4834.23 95.19  3524.85 64.21  3511.94 64.45
>>>>> 256 4   9324.63 145.74 8956.49 116.39 6720.17 73.86
>>>>> 512 1   2678.03 84.1   2630.68 82.93  2636.54 82.57
>>>>> 512 2   9368.17 195.61 9408.82 204.53 5316.3  92.99
>>>>> 512 4   9186.34 209.68 9358.72 183.82 9489.29 160.42
>>>>> 1024 1  3620.71 109.88 3625.54 109.83 3606.61 112.35
>>>>> 1024 2  9429    258.32 7082.79 120.55 7403.53 134.78
>>>>> 1024 4  9430.66 290.44 9499.29 232.31 9414.6  190.92
>>>>> 4096 1  9339.28 296.48 9374.23 372.88 9348.76 298.49
>>>>> 4096 2  9410.53 378.69 9412.61 286.18 9409.75 278.31
>>>>> 4096 4  9487.35 374.1  9556.91 288.81 9441.94 221.64
>>>>> 16384 1 9380.43 403.8  9379.78 399.13 9382.42 393.55
>>>>> 16384 2 9367.69 406.93 9415.04 312.68 9409.29 300.9
>>>>> 16384 4 9391.96 405.17 9695.12 310.54 9423.76 223.47
>>>> Trying to understand the performance results:
>>>>
>>>> What is the host device configuration?  tap + bridge?
>> Yes.
>>>> Did you use host CPU affinity for the vhost threads?
>> I use numactl to pin cpu threads and vhost threads in the same numa node.
>>>> Can multiqueue tap take advantage of multiqueue host NICs or is
>>>> virtio-net multiqueue unaware of the physical NIC multiqueue
>>>> capabilities?
>> Tap is unware of the physical multiqueue NIC, but we can benefit from it
>> since we use multiple vhost threads.
> I wonder if it makes a difference to bind tap queues to physical NIC
> queues.  Maybe this is only possible in macvlan or can you preset the
> queue index of outgoing skbs so the network stack doesn't recalculate
> the flow?

There are some issues here:

- For tap, we know nothing about the physical card, especially how many
queues it has.
- We can present the queue index information in the skb. But there's not
a standard txq selection / rxq smp affinity setting method for
multiqueue card driver in linux. For example, ixgbe and efx use
completely different method. So we can easily find a method for ixgbe
but not all others.

>>>> The results seem pretty mixed - as a user it's not obvious what to
>>>> choose as a good all-round setting.
>>> Yes, this I think is the reason it's disabled by default ATM,
>>> guest admin has to enable it using ethtool.
>>>
>>> From what I saw, it looks like with a streaming guest to external
>>> benchmark, we sometimes get smaller packets and
>>> so worse performance. We are still investigating - what's
>>> going on seems to be a strange interaction with guest TCP stack.
>> Yes, guest TCP tends to batch less when the multiqueue is enabled
>> (latency is improved). So much more smaller packets were sent in this
>> case leads to bad performance.
> Okay, this makes sense.
>
>>> Other workloads seem to benefit.
>>>
>>>>  Any observations on how multiqueue
>>>> should be configured?
>>> I think the right thing to do is to enable it on the host and
>>> let guest admin enable it if appropriate.
>>>
>>>> What is the "norm" statistic?
>> Sorry for not being clear, it's short for normalized result (divide the
>> result by cpu utilization).
> Okay, that explains the results a little.  When norm doesn't change much
> across 1q/2q/4q we're getting linear scaling.  It scales further because
> the queues allow for more CPUs to be used.  That's good.
>
> Stefan
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