Re: IO speed limited by size of IO request (for RBD driver)

[Steven Haigh <netwiz@crc.id.au>]

On 29/04/2013 6:38 PM, Roger Pau Monné wrote:
> Did you also copy xen-blkfront?

Dammit! No, no I didn't. I tried to just copy this back over to the 
3.8.8 and 3.8.10 kernel versions, but it came up with too many errors - 
so I just rebuilt/packages the checkout of your git based on 3.8.0-rc7.

> It seems you are missing some pieces, you should see something like:
>
> blkfront: xvda: flush diskcache: enabled; persistent grants: enabled;
> indirect descriptors: enabled;

Now I'm running 3.8.0-rc7 from your git on both DomU and Dom0. In the 
DomU, I now see:

blkfront: xvda: flush diskcache: enabled; persistent grants: enabled; 
indirect descriptors: enabled;

 From what you say, this should be what I'd expect.

 From the DomU:
# dd if=/dev/zero of=output.zero bs=1M count=2048
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 32.9252 s, 65.2 MB/s

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
            0.23    0.00    9.61    0.00    0.46   89.70

Device:         rrqm/s   wrqm/s     r/s     w/s    rMB/s    wMB/s 
avgrq-sz avgqu-sz   await  svctm  %util
sdd            1071.40  7914.87   67.28  479.18     4.40    32.64 
138.82    17.45   31.65   2.00 109.36
sde            1151.72  7943.71   68.65  486.73     4.79    33.20 
140.10    13.18   23.87   1.93 107.14
sdc            1123.34  7921.05   66.36  482.84     4.66    32.86 
139.89     8.80   15.96   1.86 102.31
sdf            1091.53  7937.30   70.02  483.30     4.54    32.97 
138.84    18.98   34.31   1.98 109.45
md2               0.00     0.00    0.00 1003.66     0.00    65.31 
133.27     0.00    0.00   0.00   0.00

# dd if=/dev/zero of=output.zero bs=1M count=2048 oflag=direct
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 25.4705 s, 84.3 MB/s

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
            0.22    0.00   10.94    0.00    0.22   88.62

Device:         rrqm/s   wrqm/s     r/s     w/s    rMB/s    wMB/s 
avgrq-sz avgqu-sz   await  svctm  %util
sdd              20.35 13703.72    1.75  258.64     0.10    54.54 
429.75     0.47    1.81   1.13  29.34
sde            1858.64 11655.36   61.05  199.56     7.51    46.36 
423.36     1.54    5.89   3.27  85.27
sdc             142.45 11824.07    5.47  254.70     0.59    47.18 
376.03     0.42    1.61   1.02  26.59
sdf             332.39 13489.72   11.38  248.80     1.35    53.72 
433.47     1.06    4.10   2.50  65.16
md2               0.00     0.00    3.72  733.48     0.06    91.68 
254.86     0.00    0.00   0.00   0.00


-- 
Steven Haigh

Email: netwiz@crc.id.au
Web: https://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897
Fax: (03) 8338 0299