On 05/08/2014 10:22 AM, Peter Lieven wrote: > this patch tries to optimize zero write requests > by automatically using bdrv_write_zeroes if it is > supported by the format. > > This significantly speeds up file system initialization and > should speed zero write test used to test backend storage > performance. >
> Signed-off-by: Peter Lieven <p...@kamp.de>
> ---
> v3->v4: - use QAPI generated enum and lookup table [Kevin]
> - added more details about the options in the comments
> of the qapi-schema [Eric]
> - changed the type of detect_zeroes from str to
> BlockdevDetectZeroesOptions. I left the name
> as is because it is consistent with e.g.
> BlockdevDiscardOptions or BlockdevAioOptions [Eric]
> - changed the parse function in blockdev_init to
> be generic usable for other enum parameters
If you wouldn't mind, I think the generic function is useful enough that
people might want to backport it independently from this optimization.
It would be better to split this into a two-patch series, one for the
new parse_enum_option, the other for bdrv_write_zeroes utilizing it.
> + },{
> + .name = "detect-zeroes",
> + .type = QEMU_OPT_STRING,
> + .help = "try to optimize zero writes",
Might be worth listing (off, on, unmap) in the text.
Everything else looked okay, but I'll wait for R-b until I see a
response about the idea of splitting the patch (even if that response is
justification for keeping it as one)
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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