[Qemu-devel] [PATCH 0/2] qcow2 metadata cache

[Kevin Wolf <kwolf@redhat.com>]

block-queue turned out to be too big effort to be useful for quickly fixing the
performance problems that qcow2 got since we introduced the metadata flushes.
While I still think the idea is right, it needs more time and qcow2 doesn't
have more time. Let's come back to block-queue later when the most urgent qcow2
problems are fixed.

So this is the idea of block-queue applied to the very specific case of qcow2.
Whereas block-queue tried to be a generic solution for all kind of things and
tried to make all writes asynchronous at the same time, this is only about
batching writes to refcount blocks and L2 tables in qcow2 and getting the
dependencies right. (Yes, the L1 table and refcount table is left alone. They
are almost never written to anyway.)

This should be much easier to understand and review, and I myself feel a bit
more confident about it than with block-queue, too.

v1:
- Don't read newly allocated tables from the disk before memsetting them to
  zero

Kevin Wolf (2):
  qcow2: Add QcowCache
  qcow2: Use QcowCache

 Makefile.objs          |    2 +-
 block/qcow2-cache.c    |  284 ++++++++++++++++++++++++++++++++++++++++++++++++
 block/qcow2-cluster.c  |  206 ++++++++++++-----------------------
 block/qcow2-refcount.c |  249 +++++++++++++++++-------------------------
 block/qcow2.c          |   43 +++++++-
 block/qcow2.h          |   31 +++++-
 6 files changed, 520 insertions(+), 295 deletions(-)
 create mode 100644 block/qcow2-cache.c

-- 
1.7.2.3