Xen devel - Oct 2006 - [PATCH][Take 3-2][Resend] Sysfs Interface for balloon driver

This mail is resend mail.
But, the units is modified by result of discussion.
The attached patch is final version.

Have anyone comments?


Hi. 

This patch provides a sysfs interface for the balloon driver (Take 3).

Currently, the interface for the balloon driver is provided by procfs.
However, I was suggested by Kier and Anthony that procfs should handle  only
process information and other information should be located in sysfs,
  when I made the interface for virtual block devices.

The information for the balloon driver also should be moved to sysfs.
So, I have made a sysfs interface for the balloon driver.

The information for balloon driver is placed in /sys/devices/system/memory/.

For Take 2 patch, this patch modifies only target_kibi_bytes is kept in
/sys/devices/system/memory/memory0 as parameter, and other information (ex.
current_kibi_bytes) is moved to info sub directory.

The hard limit is remained for the present.
Perhaps, anyone maybe used at someday, and it may be useful now.


Example outputs of the sysfs interface of the balloon driver are as follows:

 Example 1.  Show each information

[root@Dom0 ~]# ls -al /sys/devices/system/memory/memory0/
total 0
drwxr-xr-x 3 root root    0 Oct  2 20:13 .
drwxr-xr-x 3 root root    0 Oct  3  2006 ..
drwxr-xr-x 2 root root    0 Oct  2 20:11 info
-rw-r--r-- 1 root root 4096 Oct  2 20:13 target_kB [root@Dom0 ~]# cat
/sys/devices/system/memory/memory0/target_kB
262144
[root@noir ~]# ls -al /sys/devices/system/memory/memory0/info/
total 0
drwxr-xr-x 2 root root    0 Oct  2 20:11 .
drwxr-xr-x 3 root root    0 Oct  2 20:13 ..
-r--r--r-- 1 root root 4096 Oct  2 20:14 current_kB
-r--r--r-- 1 root root 4096 Oct  2 20:14 driver_kB
-r--r--r-- 1 root root 4096 Oct  2 20:14 hard_limit_kB
-r--r--r-- 1 root root 4096 Oct  2 20:14 high_kB
-r--r--r-- 1 root root 4096 Oct  2 20:14 low_kB [root@Dom0 ~]# cat
/sys/devices/system/memory/memory0/info/current_kB
262144
[root@Dom0 ~]# cat /sys/devices/system/memory/memory0/info/driver_kB
1024
[root@Dom0 ~]# cat /sys/devices/system/memory/memory0/info/hard_limit_kB
???
[root@Dom0 ~]# cat /sys/devices/system/memory/memory0/info/high_kB
0
[root@Dom0 ~]# cat /sys/devices/system/memory/memory0/info/low_kB
509952


 Example 2. Set memory size of a domain

[root@Dom0 ~]# echo 1024M > /sys/devices/system/memory/memory0/target_kB
[root@Dom0 ~]# cat /sys/devices/system/memory/memory0/target_kB
1048576
[root@Dom0 ~]# cat /sys/devices/system/memory/memory0/info/current_kB
758192
[root@Dom0 ~]# cat /sys/devices/system/memory/memory0/info/hard_limit_kB
758192
[root@Dom0 ~]# cat /sys/devices/system/memory/memory0/info/driver_kB
1024



Regards
Satoshi UCHIDA 
   NEC Corporation, Japan


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On 20/10/06 11:32 am, "Satoshi Uchida" <s-uchida@ap.jp.nec.com>
wrote:
> This mail is resend mail.
> But, the units is modified by result of discussion.
> The attached patch is final version.
> 
> Have anyone comments?
I don''t remember the precise details of the debate about the sysfs
names,
but <foo>_kibi_bytes isn''t going to get checked in. I hate that
stupid
naming scheme, especially where noone is likely to get confused between
whether 10^3 and 2^10 is meant. And the suffix is rather long too: it dwarfs
the interesting bit of the name.

Can I just ''s/kibi_bytes/kb/g'' when I check this in?
Noone''s going to get
confused that it''s units of 10^3-bits or 10^3-bytes or 2^10-bits.

 -- Keir



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On Fri, Oct 20, 2006 at 08:17:03PM +0100, Keir Fraser wrote:
> I don''t remember the precise details of the debate about the sysfs
names,
> but <foo>_kibi_bytes isn''t going to get checked in. I hate
that stupid
> naming scheme, especially where noone is likely to get confused between
> whether 10^3 and 2^10 is meant. And the suffix is rather long too: it
dwarfs
> the interesting bit of the name.
> 
> Can I just ''s/kibi_bytes/kb/g'' when I check this in?
Noone''s going to get
> confused that it''s units of 10^3-bits or 10^3-bytes or 2^10-bits.
Please! This is what I was asking for...

regards
john

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> 
> Can I just ''s/kibi_bytes/kb/g'' when I check this in?
Noone''s
> going to get confused that it''s units of 10^3-bits or 
> 10^3-bytes or 2^10-bits.
> 
No problem.
I think that ''s/kibi_bytes/kib/g'' may be also fine.

The most important one is to be able to take information.
Next, it is important that anyone can understand easily and clearly.

We discussed which representations is more better.
However, there are many representation in the field and
there are traditional representation in each field.
  Ex. If based on formal, it should represented at ''KiB'' (kilo
binary bytes).
       In xenmon, this representation is also used. (ex.MiB)
       However, traditional representation is ''kb'' in sysfs
(block and memory field)
      and no computer engineers is going to mistake as you say.
        
I can not decided that which formal or traditional representation is better.

Thanks,
Satoshi UCHIDA


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