[Sheepdog] Sheepdog performance

[Chris Webb]

Haven <haven at thehavennet.org.uk> writes:

> I'm seeing higher results with cache=writeback.
> 
> A few comparison runs show thats there's a decent bit of variation per run:
> writeback: 41.1, 41.2, 39.3, 39.7, 39.1
> none: 42.2, 33.3, 35.2, 30.4, 30.6
> 
> I know these tests are not very conclusive but I'm not seeing a huge
> difference between the two cache modes.

I think this is because the sheepdog driver doesn't use the value of the
cache drive flag at all, if you take a look at block/sheepdog.c. Apparently
only the drivers that layer on top of raw-posix.c or raw-win32.c for local
device/file access use the relevant bits from bs->open_flags.

Cheers,

Chris.