Re: [Qemu-devel] Data classification in Qemu

[Wu Libin]

Yeah, i know dm-cache, it’s in the layer of block.

Maybe my description is not clear enough.Just because i see a patch, it will 
set flags which can classify IO size in bio->bi_flags, and in the function 
sd_prep_fn, it will set the SCSI command depends on the bio->bi_flags, like:
SCpnt->cmnd[6] = DSS_BIO_CLASS(SCpnt->request->bio);

And i see the data classification function will be enabled when the device 
model is “QEMU”, so i guess the QEMU must can recognise the SCSI command. 
That’s why i will search the data classification about the QEMU.

It’s true QEMU not care about the filesystem, but we have flags, right, -:).

On 16 Sep, 2014, at 10:46 pm, Stefan Hajnoczi <address@hidden> wrote:

> On Tue, Sep 16, 2014 at 12:06:21AM +0800, Wu Libin wrote:
>> I’m wondering if the Qemu has the data classification function.I means it 
>> can classify the file size like 4K, 8K, 16K,…,4M,…1G, and do some cache 
>> policies with SSD.
>> 
>> Anyone can tell me about this? I search the list and find nothing. Sorry if 
>> it already exists on the mail list.
> 
> Not sure what you are trying to do.
> 
> QEMU system emulation only deals with block devices, it is not aware of
> the file system inside the guest.
> 
> Have you looked at dm-cache which can be used with LVM?
> 
> Stefan