Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated()

[Dmitry Konishchev]

On Wed, Jun 15, 2011 at 5:57 PM, Stefan Hajnoczi <address@hidden> wrote:
> Anyway, bdrv_getlength() will return the total_sectors value instead
> of calling into raw-posix.c .bdrv_getlength().  That's why it should
> be cheap.

Yeah, I see it now after a closer look in the drivers code. It looks
like I get this 9% slowdown just because for my particular test
bdrv_get_geometry() is called 37,348,536 times, which is a big number
even for function which calls another function which checks a few IFs
and returns a multiplication of two numbers.

Anyway, I think that caching the geometry is a good thing to do, so I
believe that the second version of the patch is good enough.

-- 
Dmitry Konishchev
mailto:address@hidden