Huge memory leak in virtio, see kvm-Bugs-2989366

[Leszek Urbanski <tygrys@moo.pl>]

Hi,

this is a follow-up to bug 2989366:

https://sourceforge.net/tracker/?func=detail&atid=893831&aid=2989366&group_id=180599

after extensive debugging with the guys on #kvm it turns out that the leak is
in the qemu-kvm userland process, in virtio-blk.

A summary of my setup is described in the bug report above.

The affected guests have a common load profile: frequent sequential I/O on
large (~ 2 GB) files.

I tried switching off or changing almost all options in my qemu command
line and the only option that makes a difference is -drive if=virtio.

When an affected guest is run with virtio drives the qemu-kvm process starts
leaking immediately after startup and grows (for the most heavily leaking
guests) by ~ 1 GB RSS for every ten hours (and keeps growing until OOM).

With -drive if=ide or scsi, it doesn't leak at all.

A diff of /proc/<pid>/maps of an affected qemu-kvm at startup and after
1.5 hrs:

-039b9000-5ccd0000 rw-p 00000000 00:00 0
+039b9000-65803000 rw-p 00000000 00:00 0

(a heap leak?)

I'm willing to debug further. The problem is 100% reproducible.


-- 
Leszek "Tygrys" Urbanski, SCSA, SCNA
 "Unix-to-Unix Copy Program;" said PDP-1. "You will never find a more
  wretched hive of bugs and flamers. We must be cautious." -- DECWARS
     http://cygnus.moo.pl/ -- Cygnus High Altitude Balloon