[Qemu-devel] Re: [PATCH 13/13] blockdev: New -blockdev to define a host block device
On 06/10/2010 06:32 PM, Markus Armbruster wrote: I understand why that's the most sensible cache setting. But if the user explicitly asks for something else, I think we better give it to him, or tell him no. Ignoring him silently isn't nice. Ah, it's clearer now... I guess one could use cache=something together with snapshot to do benchmarking. Actually the same changes in behavior (unsafe as default, but observe a non-default value) can be done to -drive ...,snapshot too. Maybe I'll give it a shot. Paolo
[Qemu-devel] Re: [PATCH 13/13] blockdev: New -blockdev to define a host block device
Paolo Bonzini writes:
> On 06/02/2010 06:55 PM, Markus Armbruster wrote:
>> * Like -drive, -blockdev ignores cache= silently when snapshot=on. Do
>>we really want that?
>
> Yes, the changes are throw-away by definition. Might as well use
> cache=unsafe.
I understand why that's the most sensible cache setting. But if the
user explicitly asks for something else, I think we better give it to
him, or tell him no. Ignoring him silently isn't nice.
>> +if (snapshot) {
>> +/* always use write-back with snapshot */
>> +/* FIXME ignores explicit cache= *silently*; really want that? */
>> +flags &= ~BDRV_O_CACHE_MASK;
>> +flags |= (BDRV_O_SNAPSHOT | BDRV_O_CACHE_WB);
>> +flags |= BDRV_O_SNAPSHOT;
>
> Cut and paste?
Pasto indeed, will fix. Thanks!
[Qemu-devel] Re: [PATCH 13/13] blockdev: New -blockdev to define a host block device
On 06/02/2010 06:55 PM, Markus Armbruster wrote:
* Like -drive, -blockdev ignores cache= silently when snapshot=on. Do
we really want that?
Yes, the changes are throw-away by definition. Might as well use
cache=unsafe.
+if (snapshot) {
+/* always use write-back with snapshot */
+/* FIXME ignores explicit cache= *silently*; really want that? */
+flags &= ~BDRV_O_CACHE_MASK;
+flags |= (BDRV_O_SNAPSHOT | BDRV_O_CACHE_WB);
+flags |= BDRV_O_SNAPSHOT;
Cut and paste?
Paolo
