qemu/docs/qcow2-cache.txt

6 This work is licensed under the terms of the GNU GPL, version 2 or
15 This document attempts to give an overview of the L2 and refcount
89 (16), this becomes:
106 cluster size of 64 KB, it is 256 KB (262144 bytes). This is sufficient for
129    for full coverage of 256 GB images, with the default cluster size). This
132    of this max. value.
134    this difference stems from the fact that on Linux the cache can be cleared
151 (this can change if you are using internal snapshots, so you may want
155 L2 cache size. This resulted in unnecessarily large caches, so now the
161 The qcow2 L2 cache can store complete tables. This means that if QEMU
166 This can be inefficient with large cluster sizes since it results in
170 it smaller than the cluster size. This can be configured using the
184    disk I/O faster. This is particularly true with solid state drives
194  - Only the L2 cache can be configured this way. The refcount cache
199    configure the cache sizes" sections in this document) then none of
200    this is necessary and you can omit the "l2-cache-entry-size"
201    parameter altogether. In this case QEMU makes the entry size
212 interval are removed from memory. Setting this parameter to 0 disables this
219 If unset, the default value for this parameter is 600 on platforms which
220 support this functionality, and is 0 (disabled) on other platforms.
222 This functionality currently relies on the MADV_DONTNEED argument for
223 madvise() to actually free the memory. This is a Linux-specific feature,
229 All numbers shown in this document are valid for qcow2 images with normal
241 Refcount blocks are not affected by this.