[0/4] Introduction of l2-cache-full option for qcow2 images

Message

Leonid Bloch July 24, 2018, 12:17 p.m. UTC

This series introduces an option to calculate and allocate
automatically enough qcow2 L2 cache to cover the entire image.
Using cache that covers the entire image can benefit performance,
while having only a small memory overhead (just 1 MB for every 8 GB
of virtual image size with the default cluster size).

Leonid Bloch (4):
  qcow2: Introduce an option for sufficient L2 cache for the entire
    image
  docs: Fix an inaccuracy due to recent changes
  docs: Document the l2-cache-full option
  iotests: Add tests for the new l2-cache-full option

 block/qcow2.c              | 37 +++++++++++++++++++++++++++++--------
 block/qcow2.h              |  1 +
 docs/qcow2-cache.txt       | 18 +++++++++++-------
 qapi/block-core.json       |  4 ++++
 qemu-options.hx            |  4 ++++
 tests/qemu-iotests/103     |  6 ++++++
 tests/qemu-iotests/103.out |  4 +++-
 tests/qemu-iotests/137     |  2 ++
 tests/qemu-iotests/137.out |  4 +++-
 9 files changed, 63 insertions(+), 17 deletions(-)

Comments

Eric Blake July 24, 2018, 2:49 p.m. UTC | #1

On 07/24/2018 07:17 AM, Leonid Bloch wrote:
> This series introduces an option to calculate and allocate
> automatically enough qcow2 L2 cache to cover the entire image.
> Using cache that covers the entire image can benefit performance,
> while having only a small memory overhead (just 1 MB for every 8 GB
> of virtual image size with the default cluster size).

Is this still needed after Berto's work on commit 603790e and related, 
that maximizes the l2 cache by minimizing the refcount cache?

Leonid Bloch July 24, 2018, 3:19 p.m. UTC | #2

On 07/24/2018 05:49 PM, Eric Blake wrote:

     On 07/24/2018 07:17 AM, Leonid Bloch wrote:

     This series introduces an option to calculate and allocate
     automatically enough qcow2 L2 cache to cover the entire image.
     Using cache that covers the entire image can benefit performance,
     while having only a small memory overhead (just 1 MB for every 8 GB
     of virtual image size with the default cluster size).

     Is this still needed after Berto's work on commit 603790e and
     related, that maximizes the l2 cache by minimizing the refcount
     cache?

   Yes. In the commits you refer to, the L2 cache was set to cover all the
   image size only in the case that the combined cache size is set, and is
   larger than max_l2_cache+min_refcount_cache. This series adds an option
   to set the L2 cache to cover the entire image without the need to
   calculate the required size externally, and without dependency on the
   combined cache size setting.