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[Qemu-block] [PATCH v2 0/5] qcow2: Make the L2 cache cover the whole ima
From: |
Leonid Bloch |
Subject: |
[Qemu-block] [PATCH v2 0/5] qcow2: Make the L2 cache cover the whole image by default |
Date: |
Tue, 7 Aug 2018 23:21:17 +0300 |
This series makes the qcow2 L2 cache cover the entire image by default.
The importance of this change is in noticeable performance improvement,
especially with heavy random I/O. The memory overhead is not big in most
cases, as only 1 MB of cache for every 8 GB of image size is used.
For cases with very large images and/or small cluster sizes, or systems
with limited RAM resources, there is an upper limit on the default L2
cache: 32 MB. To modify this limit one can use the already existing
'l2-cache-size' and 'cache-size' options. Moreover, this fixes the
behavior of 'l2-cache-size', as it was documented as the *maximum* L2
cache size, but in practice behaved as an absolute size.
To compensate the memory overhead which may be increased following this
behavior, the default cache-clean-interval is set to 30 seconds by
default (was disabled by default before).
The L2 cache is also resized accordingly, by default, if the image is
resized.
Additionally, few minor changes are made (refactoring and documentation
fixes).
Differences from v1:
* .gitignore modification patch removed (unneeded).
* The grammar fix in conflicting cache sizing patch removed (merged).
* The update total_sectors when resizing patch squashed with the
resizing patch.
* L2 cache is now capped at 32 MB.
* The default cache-clean-interval is set to 30 seconds.
Leonid Bloch (5):
qcow2: Options' documentation fixes
qcow2: Make the default L2 cache sufficient to cover the entire image
qcow2: Resize the cache upon image resizing
qcow2: Set the default cache-clean-interval to 30 seconds
qcow2: Explicit number replaced by a constant
block/qcow2.c | 47 +++++++++++++++++++-------------------
block/qcow2.h | 5 ++--
docs/qcow2-cache.txt | 30 ++++++++++++++----------
qapi/block-core.json | 3 ++-
qemu-options.hx | 11 +++++----
tests/qemu-iotests/137 | 1 -
tests/qemu-iotests/137.out | 1 -
7 files changed, 53 insertions(+), 45 deletions(-)
--
2.17.1
- [Qemu-block] [PATCH v2 0/5] qcow2: Make the L2 cache cover the whole image by default,
Leonid Bloch <=
- [Qemu-block] [PATCH v2 1/5] qcow2: Options' documentation fixes, Leonid Bloch, 2018/08/07
- [Qemu-block] [PATCH v2 5/5] qcow2: Explicit number replaced by a constant, Leonid Bloch, 2018/08/07
- [Qemu-block] [PATCH v2 3/5] qcow2: Resize the cache upon image resizing, Leonid Bloch, 2018/08/07
- [Qemu-block] [PATCH v2 4/5] qcow2: Set the default cache-clean-interval to 30 seconds, Leonid Bloch, 2018/08/07
- [Qemu-block] [PATCH v2 2/5] qcow2: Make the default L2 cache sufficient to cover the entire image, Leonid Bloch, 2018/08/07