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RE: [Xen-devel] [PATCH] Sysfs Interface for balloon driver

To: "'John Levon'" <levon@xxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Sysfs Interface for balloon driver
From: "Satoshi Uchida" <s-uchida@xxxxxxxxxxxxx>
Date: Wed, 20 Sep 2006 12:00:36 +0900
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Thanks John.

> >     [root@Dom0 ~]# cat 
> /sys/bus/xen/drivers/balloon/statistics/balloon_high
> >           0 kB
> 
> It's very unusual to have units in a sysfs node. I believe 
> this should just be the number, and documented elsewhere what 
> the units are.

I also hesitated that there give units or not.
First, units are not given.
However, I myself didn't understand units which is byte? or pages?.
In procfs, It is easy to understand because there have units.
So, in this time, I take them units.

As you say, it should be remove.


> I also don't quite get the location. I don't quite think of 
> balloon as a real "driver" as such, it's core kernel 
> functionality rather. Wouldn't 
> /sys/hypervisor/properties/balloon/ be a more sensible place?

In this time, it locate by following reason.
  A balloon driver is similar to front-end driver.
   1. It does not handle real device.
       Namely, by virtualization technology,
       it feign to handle computer elements. 
   2. Its computer elements is handled in 
       Domain (VM).
       Namely, it does not handle the whole real environments,
       and Its information is valid for VM.

I feel that the term "hypervisor" means VMM in general.
And a balloon exists for VM, and not for VMM.
Therefore, I think that such information should not be located to 
/sys/hypervisor.

Should new location make for storing such (VM's) information ?
For example, as following.
  /sys/virtualization -+--- domain
                             +--- hypervisor

Tnaks your reply.

Regards
Satoshi UCHIDA 
   NEC Corporation, Japan



> -----Original Message-----
> From: John Levon [mailto:levon@xxxxxxxxxxxxxxxxx] 
> Sent: Wednesday, September 20, 2006 10:13 AM
> To: Satoshi Uchida
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] [PATCH] Sysfs Interface for balloon driver
> 
> On Wed, Sep 20, 2006 at 09:26:43AM +0900, Satoshi Uchida wrote:
> 
> >     [root@Dom0 ~]# cat 
> /sys/bus/xen/drivers/balloon/statistics/balloon_high
> >           0 kB
> 
> It's very unusual to have units in a sysfs node. I believe 
> this should just be the number, and documented elsewhere what 
> the units are.
> 
> I also don't quite get the location. I don't quite think of 
> balloon as a real "driver" as such, it's core kernel 
> functionality rather. Wouldn't 
> /sys/hypervisor/properties/balloon/ be a more sensible place?
> 
> regards,
> john
> 


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