[xfs-masters] how to use fstrim?

[Stefan Priebe]

Am 27.07.2013 03:50, schrieb Dave Chinner:
> On Fri, Jul 26, 2013 at 08:17:21PM +0200, Stefan Priebe wrote:
>> Hi,
>>
>> what is the right way to use fstrim on top of XFS? just doing fstrim
>> -v -m 4194304 /
>>
>> results sometimes (might depend on disk i/o) to hanging tasks and
>> stack traces - fstrim needs > 5 min in these cases.
>
> It does indeed depend on disk IO. XFS walks all the free space and
> issues discards on it, so runtime is always O(freespace). And while
> it is walking an AG discarding the free space, it will hold the AG
> locked so that free space doesn't change. This can hang other
> operations for the length of time it takes to discard all the free
> space in the AG.
 > IOWs, the behaviour of fstrim on XFS is entirely dependent on the
 > speed of the block layer and hardware implementations of discards.

Yes OK i understand that but is there any way to prevent getting the 
whole server crash when I/O is too much?

For example splitting whole disk or even AGs into subparts? Or set a 
timeout for the fstrim command?

Greets,
Stefan