FreeBSD 5.3 I/O Performance / Linux 2.6.10 | Continued Discussion

[Robert Watson]

On Wed, 26 Jan 2005, Mike Tancsa wrote:

> At 01:47 PM 26/01/2005, Nick Pavlica wrote:
> >All,
> >   With the recent release of 4.11 I thought that I would give it a
> 
> Yes, I found the same thing basically.  My test box is a P4 3Ghz with 2G
> of RAM on a 3ware 8605 controller with 4 drives in RAID5.  Virtually
> every test I did with iozone* showed a difference anywhere from 10-40%
> in favor of RELENG_4. 
> 
> Note, this is a 2G RAM machine hence the odd result for the 1.5G test

While it's not for the feint of heart, it might be interesting to see how
results compare in 6-CURRENT + debugging of various sorts (including
malloc) turned off, and debug.mpsafevfs turned on.  One possible issue
with the twe/twa drivers is that they are currently MPSAFE, so may see
substantial contention (and hence additional latency).  The move to an
MPSAFE VFS will help with that a lot, I should think.

Also, while on face value this may seem odd, could you try the following
additional variables:

- Layer the test UFS partition directly over ad0 instead of ad0s1a
- UFS1 vs UFS2

Also please make sure that background fsck is not running during the
tests, and that no snapshots are currently defined on the test file
system.

Finally, in as much as is possible, make sure that the layout of the disks
is approximately the same -- as countless benchmarking papers show, there
are substantial differences (10%+) in I/O throughput depending on where on
the disk surface operations occur.  That's one of the reasons to try UFS1
for the test partition, although not the only one.

Robert N M Watson



> 
>                -------Sequential Output--------  ---Sequential Input-- 
> --Random--
>                -Per Char- --Block--- -Rewrite--  -Per Char- --Block--- 
> --Seeks---
> Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU  K/sec %CPU K/sec %CPU  /sec 
> %CPU
> 4        1500 37673 23.7 37848  6.6 40784  7.7  97064 99.8 1174906 99.4 
> 89867.4 99.6
> 4        3000 38492 24.6 38753  7.0 18396  4.1  80355 
> 86.0  92051   9.9   605.1  1.0
> 5        1500 31226 23.0 34529  7.9 36444  8.9 110295 99.8  983156 92.5 
> 27388.8 99.6
> 5        3000 33820 26.1 34309  8.3 13339  3.7  59807 
> 56.8  68059   9.8   330.8  0.9
> 
> 
> And a local postmark test. RELENG_4 and RELENG_5
> 
> pm>set size 300 100000
> pm>set location /card0-a
> pm>set transactions 400000
> pm>run
> Creating files...Done
> Performing transactions..........Done
> Deleting files...Done
> Time:
>          1219 seconds total
>          1219 seconds of transactions (328 per second)
> 
> Files:
>          200107 created (164 per second)
>                  Creation alone: 500 files (500 per second)
>                  Mixed with transactions: 199607 files (163 per second)
>          199905 read (163 per second)
>          199384 appended (163 per second)
>          200107 deleted (164 per second)
>                  Deletion alone: 889 files (889 per second)
>                  Mixed with transactions: 199218 files (163 per second)
> 
> Data:
>          12715.55 megabytes read (10.43 megabytes per second)
>          12728.92 megabytes written (10.44 megabytes per second)
> pm>
> 
> 
> pm>set size 300 100000
> pm>set location /card0-a
> pm>set transactions 400000
> pm>run
> Creating files...Done
> Performing transactions..........Done
> Deleting files...Done
> Time:
>          2824 seconds total
>          2822 seconds of transactions (141 per second)
> 
> Files:
>          200107 created (70 per second)
>                  Creation alone: 500 files (500 per second)
>                  Mixed with transactions: 199607 files (70 per second)
>          199905 read (70 per second)
>          199384 appended (70 per second)
>          200107 deleted (70 per second)
>                  Deletion alone: 889 files (889 per second)
>                  Mixed with transactions: 199218 files (70 per second)
> 
> Data:
>          12715.55 megabytes read (4.50 megabytes per second)
>          12728.92 megabytes written (4.51 megabytes per second)
> pm>
> 
> 
> *I have the iozone results in 2 .xls files if anyone wants to see them at
> 
> http://www.tancsa.com/iozone-r5vsr4.zip
> 
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