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From Jan Hlavatý <hla...@code.cz>
Subject Re: alligned Vs Non Alligned log writes ..
Date Sat, 04 Dec 2004 15:03:02 GMT
Suresh Thalamati wrote:
> 
> It would be great if  some one can run this test on other platforms and
> post the results to the list.

I have added display of percentual difference to make it easier to look at.
Results vary a lot, so dont take it for absolute.

Heres what I got on my Linux (FC3, Celeron 800, 512MB, 2 IDE DISK RAID1 ext3 fs)

[root@lin ~]# java -cp . allignWritePerfTest2 kuk.bin 128
(Buffer-Size(K) | Alligned Write(msec) |NonAlligned Write(msec)) | gain %

512 |  21.0390625  |  27.2265625 |   29.409580393613084%
512 |  20.4921875  |  26.609375  |   29.85131528783836%
512 |  20.40625    |  28.46875   |   39.50995405819296%
512                             avg ~ 33%

256 |  10.1328125  |  18.3359375 |   80.95605242868157%
256 |  10.234375   |  20.375     |   99.08396946564886%
256 |  10.0546875  |  19.3046875 |   91.996891996892%
256                             avg ~ 50%

128 |   5.3515625  |  12.96875   |  142.33576642335765%
128 |   5.1640625  |  13.6640625 |  164.59909228441757%
128 |   5.28125    |  13.125     |  148.5207100591716%
128                             avg ~151%

 64 |   2.578125   |  10.515625  |  307.8787878787879%
 64 |   2.53125    |  10.625     |  319.75308641975306%
 64 |   2.5703125  |  10.375     |  303.64741641337383%
64                              avg ~310%

 32 |   1.453125   |   2.1796875 |   50.0%
 32 |   1.3828125  |   1.8828125 |   36.15819209039549%
 32 |   1.4609375  |   1.8984375 |   29.946524064171115%
32                              avg ~ 38%

 16 |   1.1796875  |   3.015625  |  155.6291390728477%
 16 |   1.1328125  |   2.8515625 |  151.72413793103448%
 16 |   1.109375   |   2.8671875 |  158.45070422535213%
16                             avg ~155%

 12 |   1.1328125  |   2.8125    |  148.27586206896552%
 12 |   0.921875   |   2.421875  |  162.71186440677968%
 12 |   0.8046875  |   2.40625   |  199.02912621359224%
12                             avg ~169%

 10 |   2.171875   |   2.4453125 |   12.589928057553962%
 10 |   2.1796875  |   2.1484375 |   -1.4336917562723954%
 10 |   2.0625     |   2.4296875 |   17.803030303030297%
10                             avg ~  9%

  8 |   0.5078125  |   2.125     |  318.46153846153845%
  8 |   0.859375   |   1.8515625 |  115.45454545454547%
  8 |   0.4921875  |   2.3828125 |  384.12698412698415%
8                              avg ~272%

  6 |   1.6796875  |   2.6640625 |   58.6046511627907%
  6 |   2.8203125  |   2.859375  |    1.3850415512465304%
  6 |   1.28125    |   2.0703125 |   61.585365853658544%
6                              avg ~ 40%

  4 |   0.984375   |   1.6171875 |   64.28571428571428%
  4 |   1.015625   |   2.0859375 |  105.38461538461539%
  4 |   0.84375    |   1.515625  |   79.62962962962962%
4                              avg ~ 82%

  2 |   0.671875   |   0.7109375 |    5.813953488372093%
  2 |   1.0078125  |   0.6328125 |  -37.2093023255814%
  2 |   0.6640625  |   0.7890625 |   18.82352941176471%
2                              avg ~ -4%

  1 |   0.4921875  |   0.3046875 |  -38.095238095238095%
  1 |   0.25       |   0.296875  |   18.75%
  1 |   0.25       |   0.3046875 |   21.875%
1                               avg ~ -1%


Ordered by speed gain:

64   avg ~310%
8    avg ~272%
12   avg ~169%
16   avg ~155%
128  avg ~151%
4    avg ~ 82%
256  avg ~ 50%
6    avg ~ 40%
32   avg ~ 38%
512  avg ~ 33%
10   avg ~  9%
1    avg ~ -1%
2    avg ~ -4%


Here it looks like:
1) its a lot faster for some reason (you got slow disk ;))
2) we can get actual slowdown for buffer sizes not multiple of 4k
3) we get slowdown for buffers < 4k
3) we get speedup for sizes > 4k which are multiples of 4k
   (Linux uses 4k for everything)
4) best gain on 64k, 8k (about 4 times faster)


Jan

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