XFS performance oddity

[Nick Piggin]

On Tue, Nov 23, 2010 at 11:24:49PM +1100, Nick Piggin wrote:
> Hi,
> 
> Running parallel fs_mark (0 size inodes, fsync on close) on a ramdisk
> ends up with XFS in funny patterns.
> 
> procs -----------memory---------- ---swap-- -----io---- -system--
> ----cpu----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy
> id wa
> 24  1   6576 166396    252 393676  132  140 16900 80666 21308 104333  1 84 14  1
> 21  0   6712 433856    256 387080  100  224  9152 53487 13677 53732  0 55 45  0
>  2  0   7068 463496    248 389100    0  364  2940 17896 4485 26122  0 33 65  2
>  1  0   7068 464340    248 388928    0    0     0     0   66  207  0  0 100  0
>  0  0   7068 464340    248 388928    0    0     0     0   79  200  0  0 100  0
>  0  0   7068 464544    248 388928    0    0     0     0   65  199  0  0 100  0
>  1  0   7068 464748    248 388928    0    0     0     0   79  201  0  0 100  0
>  0  0   7068 465064    248 388928    0    0     0     0   66  202  0  0 100  0
>  0  0   7068 465312    248 388928    0    0     0     0   80  200  0  0 100  0
>  0  0   7068 465500    248 388928    0    0     0     0   65  199  0  0 100  0
>  0  0   7068 465500    248 388928    0    0     0     0   80  202  0  0 100  0
>  1  0   7068 465500    248 388928    0    0     0     0   66  203  0  0 100  0
>  0  0   7068 465500    248 388928    0    0     0     0   79  200  0  0 100  0
> 23  0   7068 460332    248 388800    0    0  1416  8896 1981 7142  0  1 99  0
>  6  0   6968 360248    248 403736   56    0 15568 95171 19438 110825  1 79 21  0
> 23  0   6904 248736    248 419704  392    0 17412 118270 20208 111396  1 82 17  0
>  9  0   6884 266116    248 435904  128    0 14956 79756 18554 118020  1 76 23  0
>  0  0   6848 219640    248 445760  212    0  9932 51572 12622 76491  0 60 40  0
> 
> Got a dump of sleeping tasks. Any ideas?

Oh, this is with a lot of kernel debug options, including xfs debugging
turned on. So it might not be an interesting performance measurement.