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2018-10-01qcow2: Fix cache-clean-interval documentationLeonid Bloch1-10/+10
Fixing cache-clean-interval documentation following the recent change to a default of 600 seconds on supported plarforms (only Linux currently). Signed-off-by: Leonid Bloch <lbloch@janustech.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-10-01qcow2: Set the default cache-clean-interval to 10 minutesLeonid Bloch1-2/+2
The default cache-clean-interval is set to 10 minutes, in order to lower the overhead of the qcow2 caches (before the default was 0, i.e. disabled). * For non-Linux platforms the default is kept at 0, because cache-clean-interval is not supported there yet. Signed-off-by: Leonid Bloch <lbloch@janustech.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-10-01qcow2: Increase the default upper limit on the L2 cache sizeLeonid Bloch1-6/+9
The upper limit on the L2 cache size is increased from 1 MB to 32 MB on Linux platforms, and to 8 MB on other platforms (this difference is caused by the ability to set intervals for cache cleaning on Linux platforms only). This is done in order to allow default full coverage with the L2 cache for images of up to 256 GB in size (was 8 GB). Note, that only the needed amount to cover the full image is allocated. The value which is changed here is just the upper limit on the L2 cache size, beyond which it will not grow, even if the size of the image will require it to. Signed-off-by: Leonid Bloch <lbloch@janustech.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-10-01qcow2: Assign the L2 cache relatively to the image sizeLeonid Bloch1-5/+10
Sufficient L2 cache can noticeably improve the performance when using large images with frequent I/O. Previously, unless 'cache-size' was specified and was large enough, the L2 cache was set to a certain size without taking the virtual image size into account. Now, the L2 cache assignment is aware of the virtual size of the image, and will cover the entire image, unless the cache size needed for that is larger than a certain maximum. This maximum is set to 1 MB by default (enough to cover an 8 GB image with the default cluster size) but can be increased or decreased using the 'l2-cache-size' option. This option was previously documented as the *maximum* L2 cache size, and this patch makes it behave as such, instead of as a constant size. Also, the existing option 'cache-size' can limit the sum of both L2 and refcount caches, as previously. Signed-off-by: Leonid Bloch <lbloch@janustech.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-10-01qcow2: Options' documentation fixesLeonid Bloch1-7/+14
Signed-off-by: Leonid Bloch <lbloch@janustech.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-05-15docs: Document the new default sizes of the qcow2 cachesAlberto Garcia1-17/+16
We have just reduced the refcount cache size to the minimum unless the user explicitly requests a larger one, so we have to update the documentation to reflect this change. Signed-off-by: Alberto Garcia <berto@igalia.com> Message-id: c5f0bde23558dd9d33b21fffc76ac9953cc19c56.1523968389.git.berto@igalia.com Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-03-02docs: document how to use the l2-cache-entry-size parameterAlberto Garcia1-3/+43
This patch updates docs/qcow2-cache.txt explaining how to use the new l2-cache-entry-size parameter. Here's a more detailed technical description of this feature: https://lists.gnu.org/archive/html/qemu-block/2017-09/msg00635.html And here are some performance numbers: https://lists.gnu.org/archive/html/qemu-block/2017-12/msg00507.html Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-07-31docs: fix broken paths to docs/interop/qcow2.txtPhilippe Mathieu-Daudé1-1/+1
With the move of some docs to docs/interop on d59157ea05, a reference path was not updated. Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2016-11-25docs: Specify that cache-clean-interval is only supported in LinuxAlberto Garcia1-2/+3
Make it clear that having Linux is a hard requirement for this feature. Signed-off-by: Alberto Garcia <berto@igalia.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-09-04docs: document how to configure the qcow2 L2/refcount cachesAlberto Garcia1-0/+164
QEMU has options to configure the size of the L2 and refcount caches for the qcow2 format. However, choosing the right sizes for a particular disk image is not a straightforward operation since the ratio between the cache size and the allocated disk space is not obvious and depends on the size of the cluster and the refcount entries. This document attempts to give an overview of both caches and how to configure their sizes. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: 55de928e139b1ba3f3d40fe9c6c88f30b1f36410.1438690126.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
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