[Qemu-devel] Data classification in Qemu

[Qemu-devel] Data classification in Qemu

[Wu Libin]

Hi, everyone

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.

Thanks!

Re: [Qemu-devel] Data classification in Qemu

[Stefan Hajnoczi]

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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

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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 <stefanha@gmail.com> 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

Re: [Qemu-devel] Data classification in Qemu

[Stefan Hajnoczi]

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On Tue, Sep 16, 2014 at 11:03:04PM +0800, Wu Libin wrote:
> 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, -:).

After a web search I guess you are are talking about this paper:
http://sigops.org/sosp/sosp11/current/2011-Cascais/printable/05-mesnier.pdf

The code isn't upstream and I've never heard of it.

I think you should get in touch with the authors instead.

Stefan

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Re: [Qemu-devel] Data classification in Qemu

[Wu Libin]

Cool, the document should be the design of the patch.
The patch is a lustre in intel.
Thanks,-:)

On 17 Sep, 2014, at 5:01 pm, Stefan Hajnoczi <stefanha@gmail.com> wrote:

> On Tue, Sep 16, 2014 at 11:03:04PM +0800, Wu Libin wrote:
>> 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, -:).
> 
> After a web search I guess you are are talking about this paper:
> http://sigops.org/sosp/sosp11/current/2011-Cascais/printable/05-mesnier.pdf
> 
> The code isn't upstream and I've never heard of it.
> 
> I think you should get in touch with the authors instead.
> 
> Stefan