[lkml]   [2008]   [Mar]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: deadline unfairness
Bernd Schubert wrote:
> Hello,
> some it seems the deadline scheduler is rather unfair. Below is an example
> of md-raid6 initialization of md3, md4 and md5. All three md-devices
> do share the same blockdevices (we have patched md to allow
> parallel rebuild of shared block devices, since for us the cpu is the
> bottleneck and not the block device).
> All rebuilds started basically at the same time, as you can see, md3 is already
> done and now md4 rebuilds substantially faster than md5.
> [..]
> This is basically with a 2.6.22 kernel + lustre + md-backports, but nothing
> done to the scheduler.

Hi Bernd,

There is a deadline bug in pre-2.6.24 kernels where lower-sector requests can starve
higher-sector requests; you might be hitting this bug. It was fixed by commit:

-- Aaron

 \ /
  Last update: 2008-03-22 13:19    [W:0.069 / U:0.960 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site