[RFC] virtio: Report new guest memory statistics pertinent to memory
ballooning
When using ballooning to manage overcommitted memory on a host, a system
for
guests to communicate their memory usage to the host can provide
information
that will minimize the impact of ballooning on the guests. The current
method
employs a daemon running in each guest that communicates memory statistics
to a
host daemon at a specified time interval. The host daemon aggregates this
information and inflates and/or deflates balloons according to the level of
host memory pressure. This approach is effective but overly complex since
a
daemon must be installed inside each guest and coordinated to communicate
with
the host. A simpler approach is to collect memory statistics in the virtio
balloon driver and communicate them to the host via the device config
space.
This patch implements the qemu side of the communication channel. I will
post
the kernel driver modifications in-reply to this message.
I'd like to pose a few questions concerning my implementation:
* Is there a better way to use feature codes than using one per variable?
* This patch causes the 'info balloon' monitor command to generate output
like
the following:
(qemu) info balloon
balloon: actual=1024 MB
balloon: pswapin=0 pages
balloon: pswapout=0 pages
balloon: panon=3928 KB
balloon: pgmajfault=0
balloon: pgminfault=247914
balloon: memfree=987032 KB
balloon: memtot=1020812 KB
Is this agreeable?