KELEMEN Peter wrote:
>
> Dear XFS developers,
>
> While a single bonnie++ benchmarks shows excellent[1] performance
> on my test machine, two parallel bonnie++s still excel in write
> performance, but crawl[2] in read performance. What is the effect
> I'm seeing here?
FWIW, in the following, I see not only read performance drop with 2 bonnies,
but also re-write. Are you using the same disk as the target for
the 2 bonnies? If so, I would strongly suspect disk head contention.
Delayed allocation/writes in the block output case seem to have a positive
effect: clusters of writes are fairly large; there is no such clustering
at the higher level for reads (re-write is read+write iirc).
Can you target 2 different disks for the 2 bonnies?
ananth.
>
> Peter
>
> [1]
> Version 1.01b ------Sequential Output------ --Sequential Input-
> --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
> --Seeks--
> Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec
> %CP
> xfs_1 3G 11236 99 63619 51 17625 18 10133 88 58129 28 94.9 > 0
> ------Sequential Create------ --------Random
> Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read---
> -Delete--
> files:max:min /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec
> %CP
> 16:15000:12/512 785 18 25534 101 1378 29 1582 37 24665 99 1575
> 29
>
> [2]
> Version 1.01b ------Sequential Output------ --Sequential Input-
> --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
> --Seeks--
> Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec
> %CP
> xfs_2_1 2G 10851 98 42060 38 5277 5 4261 37 4040 1 47.8 > 0
> ------Sequential Create------ --------Random
> Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read---
> -Delete--
> files:max:min /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec
> %CP
> 16:15000:12/512 313 10 22666 98 763 24 403 15 23511 99 182
> 7
>
> Version 1.01b ------Sequential Output------ --Sequential Input-
> --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
> --Seeks--
> Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec
> %CP
> xfs_2_2 2G 10620 96 42498 39 5618 5 4296 37 3987 1 47.9 > 0
> ------Sequential Create------ --------Random
> Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read---
> -Delete--
> files:max:min /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec
> %CP
> 16:15000:12/512 307 9 20354 99 804 22 428 14 23531 100 176
> 6
>
> --
> .+'''+. .+'''+. .+'''+. .+'''+. .+''
> Kelemen Péter / \ / \ / fuji@xxxxxxx
> .+' `+...+' `+...+' `+...+' `+...+'
--
--------------------------------------------------------------------------
Rajagopal Ananthanarayanan ("ananth")
Member Technical Staff, SGI.
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