Am 19.11.2012 10:54, schrieb Paolo Bonzini:
Il 19/11/2012 10:36, Stefan Priebe - Profihost AG ha scritto:
Hi Paolo,
Am 19.11.2012 09:10, schrieb Paolo Bonzini:
I'm sorry the discard requests aren't failing. Qemu / Block driver
starts to cancel a bunch of requests.
That is being done in the kernel (the guest, I think) because the UNMAPs
are taking too long.
That makes sense. RBD handles discards as buffered I/O. When i do an
mkfs.xfs on a 30GB device i see around 900 pending discard requests. rbd
finishes them all before reporting success.
If it is correct that a 3.6.7 kernel sends as many discard requests i
only the a solution in using unbuffered I/O for discards.
Do you know what is the correct way?
I think the correct fix is to serialize them in the kernel.
So you mean this is not a bug in rbd or qemu this is a general bug in
the linux kernel since they implemented discard?
Greets,
Stefan
