[Qemu-devel] [PATCH v7 6/9] qcow2: Increase the default upper limit on the L2 cache size

[Leonid Bloch <lbloch@janustech.com>]

The upper limit on the L2 cache size is increased from 1 MB to 32 MB.
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>
---
 block/qcow2.h        | 2 +-
 docs/qcow2-cache.txt | 6 +++---
 qemu-options.hx      | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index d917b5f577..e699a55d02 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -74,7 +74,7 @@
 /* Must be at least 4 to cover all cases of refcount table growth */
 #define MIN_REFCOUNT_CACHE_SIZE 4 /* clusters */
 
-#define DEFAULT_L2_CACHE_MAX_SIZE (1 * MiB)
+#define DEFAULT_L2_CACHE_MAX_SIZE (32 * MiB)
 
 #define DEFAULT_CLUSTER_SIZE (64 * KiB)
 
diff --git a/docs/qcow2-cache.txt b/docs/qcow2-cache.txt
index 69af306267..6ad1081d1a 100644
--- a/docs/qcow2-cache.txt
+++ b/docs/qcow2-cache.txt
@@ -125,8 +125,8 @@ There are a few things that need to be taken into account:
    (or the cache entry size: see "Using smaller cache sizes" below).
 
  - The default L2 cache size will cover the entire virtual size of an
-   image, up to a certain maximum. This maximum is 1 MB by default
-   (enough for image sizes of up to 8 GB with the default cluster size)
+   image, up to a certain maximum. This maximum is 32 MB by default
+   (enough for image sizes of up to 256 GB with the default cluster size)
    and it can be reduced or enlarged using the "l2-cache-size" option.
    The minimum is 2 clusters (or 2 cache entries, see below).
 
@@ -186,7 +186,7 @@ Some things to take into account:
    always uses the cluster size as the entry size.
 
  - If the L2 cache is big enough to hold all of the image's L2 tables
-   (the default behavior for images of up to 8 GB in size) then none
+   (the default behavior for images of up to 256 GB in size) then none
    of this is necessary and you can omit the "l2-cache-entry-size"
    parameter altogether.
 
diff --git a/qemu-options.hx b/qemu-options.hx
index 22e8e2d113..4c44cdbc23 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -756,7 +756,7 @@ The maximum total size of the L2 table and refcount block caches in bytes
 
 @item l2-cache-size
 The maximum size of the L2 table cache in bytes
-(default: if cache-size is not specified - 1M; otherwise, as large as possible
+(default: if cache-size is not specified - 32M; otherwise, as large as possible
 within the cache-size, while permitting the requested or the minimal refcount
 cache size)
 
-- 
2.17.1