netdev - Re: [v2 RFC PATCH 0/4] Implement multiqueue virtio-net

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Date:	Thu, 14 Oct 2010 17:47:54 +0530
From:	Krishna Kumar2 <krkumar2@...ibm.com>
To:	Krishna Kumar2 <krkumar2@...ibm.com>
Cc:	anthony@...emonkey.ws, arnd@...db.de, avi@...hat.com,
	davem@...emloft.net, kvm@...r.kernel.org,
	"Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
	rusty@...tcorp.com.au
Subject: Re: [v2 RFC PATCH 0/4] Implement multiqueue virtio-net

Krishna Kumar2/India/IBM wrote on 10/14/2010 02:34:01 PM:

> void vhost_poll_queue(struct vhost_poll *poll)
> {
>         struct vhost_virtqueue *vq = vhost_find_vq(poll);
>
>         vhost_work_queue(vq, &poll->work);
> }
>
> Since poll batches packets, find_vq does not seem to add much
> to the CPU utilization (or BW). I am sure that code can be
> optimized much better.
>
> The results I sent in my last mail were without your use_mm
> patch, and the only tuning was to make vhost threads run on
> only cpus 0-3 (though the performance is good even without
> that). I will test it later today with the use_mm patch too.

There's a significant reduction in CPU/SD utilization with your
patch. Following is the performance of ORG vs MQ+mm patch:

_________________________________________________
               Org vs MQ+mm patch txq=2
#     BW%     CPU/RCPU%         SD/RSD%
_________________________________________________
1     2.26    -1.16    .27      -20.00  0
2     35.07   29.90    21.81     0      -11.11
4     55.03   84.57    37.66     26.92  -4.62
8     73.16   118.69   49.21     45.63  -.46
16    77.43   98.81    47.89     24.07  -7.80
24    71.59   105.18   48.44     62.84  18.18
32    70.91   102.38   47.15     49.22  8.54
40    63.26   90.58    41.00     85.27  37.33
48    45.25   45.99    11.23     14.31  -12.91
64    42.78   41.82    5.50      .43    -25.12
80    31.40   7.31     -18.69    15.78  -11.93
96    27.60   7.79     -18.54    17.39  -10.98
128   23.46   -11.89   -34.41    -.41   -25.53
_________________________________________________
BW: 40.2  CPU/RCPU: 29.9,-2.2   SD/RSD: 12.0,-15.6


Following is the performance of MQ vs MQ+mm patch:
_____________________________________________________
            MQ vs MQ+mm patch
#     BW%      CPU%       RCPU%    SD%      RSD%
_____________________________________________________
1      4.98    -.58       .84      -20.00    0
2      5.17     2.96      2.29      0       -4.00
4     -.18      .25      -.16       3.12     .98
8     -5.47    -1.36     -1.98      17.18    16.57
16    -1.90    -6.64     -3.54     -14.83   -12.12
24    -.01      23.63     14.65     57.61    46.64
32     .27     -3.19      -3.11    -22.98   -22.91
40    -1.06    -2.96      -2.96    -4.18    -4.10
48    -.28     -2.34      -3.71    -2.41    -3.81
64     9.71     33.77      30.65    81.44    77.09
80    -10.69    -31.07    -31.70   -29.22   -29.88
96    -1.14     5.98       .56     -11.57   -16.14
128   -.93     -15.60     -18.31   -19.89   -22.65
_____________________________________________________
  BW: 0   CPU/RCPU: -4.2,-6.1  SD/RSD: -13.1,-15.6
_____________________________________________________

Each test case is for 60 secs, sum over two runs (except
when number of netperf sessions is 1, which has 7 runs
of 10 secs each), numcpus=4, numtxqs=8, etc. No tuning
other than taskset each vhost to cpus 0-3.

Thanks,

- KK

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