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

["Satoshi Uchida" <s-uchida@xxxxxxxxxxxxx>]

Hi.

This patch provides a sysfs interface for the balloon driver.

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/bus/xen/driver/balloon.
I thought of other locations for the information, such as /sys/class/mem or 
/sys/devices/xen, but I finally selected the place because the balloon driver 
is similar to the front-end driver.
Please comments about that location.


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

 Example 1.  Show each information

    [root@Dom0 ~]# ls /sys/bus/xen/drivers/
    balloon/  pcifront/ vbd/
    [root@Dom0 ~]# ls /sys/bus/xen/drivers/balloon/
    bind  statistics  unbind
    [root@Dom0 ~]# ls /sys/bus/xen/drivers/balloon/statistics/
    balloon_high  current_pages  hard_limit
    balloon_low   driver_pages   target_pages
    [root@Dom0 ~]# cat /sys/bus/xen/drivers/balloon/statistics/balloon_high
          0 kB
    [root@Dom0 ~]# cat /sys/bus/xen/drivers/balloon/statistics/balloon_low
       510976 kB
   [root@Dom0 ~]# cat /sys/bus/xen/drivers/balloon/statistics/current_pages
       262144 kB
   [root@Dom0 ~]# cat /sys/bus/xen/drivers/balloon/statistics/driver_pages
       1024 kB
   [root@Dom0 ~]# cat /sys/bus/xen/drivers/balloon/statistics/hard_limit
       ??? kB


 Example 2. Set memory size of a domain

   [root@Dom0 ~]# cat /sys/bus/xen/drivers/balloon/statistics/target_pages
     262144 kB
   [root@Dom0 ~]# echo 1024M > 
/sys/bus/xen/drivers/balloon/statistics/target_pages
   [root@Dom0 ~]# cat /sys/bus/xen/drivers/balloon/statistics/target_pages
    1048576 kB
   [root@Dom0 ~]# cat /sys/bus/xen/drivers/balloon/statistics/current_pages
     758192 kB
   [root@Dom0 ~]# cat /sys/bus/xen/drivers/balloon/statistics/hard_limit
     758192 kB


The information for VMs should be located one place.
I want to propose a new location for the information of VMs, for example:
  /sys/virtualization -+--- domain
                               +--- hypervisor


Regards
Satoshi UCHIDA 
   NEC Corporation, Japan

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