On 07/26/2018 01:02 PM, Kevin Wolf wrote:
Am 25.07.2018 um 16:27 hat Leonid Bloch geschrieben:
Signed-off-by: Leonid Bloch <lbl...@janustech.com>
---
docs/qcow2-cache.txt | 3 +++
qemu-options.hx | 10 ++++++----
2 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/docs/qcow2-cache.txt b/docs/qcow2-cache.txt
index 8a09a5cc5f..3673f2be0e 100644
--- a/docs/qcow2-cache.txt
+++ b/docs/qcow2-cache.txt
@@ -130,6 +130,9 @@ There are a few things that need to be taken into account:
memory as possible to the L2 cache before increasing the refcount
cache size.
+- At most two of "l2-cache-size", "refcount-cache-size", and "cache-size"
+ can be set simultaneously.
The indentation is off here, the other list items have one space more.
Unlike L2 tables, refcount blocks are not used during normal I/O but
only during allocations and internal snapshots. In most cases they are
accessed sequentially (even during random guest I/O) so increasing the
diff --git a/qemu-options.hx b/qemu-options.hx
index b1bf0f485f..13ece21cb6 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -752,15 +752,17 @@ image file)
@item cache-size
The maximum total size of the L2 table and refcount block caches in bytes
-(default: 1048576 bytes or 8 clusters, whichever is larger)
I think it would be good to still say something about the default.
Maybe something like "default: the sum of l2-cache-size and
refcount-cache-size"?
Yes, that sounds good!
@item l2-cache-size
-The maximum size of the L2 table cache in bytes
-(default: 4/5 of the total cache size)
+The maximum size of the L2 table cache.
Why did you remove "in bytes" and add a period which the other options
don't have? I prefer the old version of this line.
I removed "in bytes" because it also accepts k, M, G, ... but on a
second thought, these are amounts of bytes as well, so changing back to
the old version.
+(default: if cache-size is not defined - 1048576 bytes or 8 clusters, whichever
+is larger; otherwise, as large as possible or needed within the cache-size,
+while permitting the requested or the minimal refcount cache size)
@item refcount-cache-size
The maximum size of the refcount block cache in bytes
-(default: 1/5 of the total cache size)
+(default: 4 times the cluster size, or any portion of the cache-size, if it is
+specified and large enough, left over after allocating the full L2 cache)
I found the second part hard to understand. Maybe "4 times the cluster
size; or if both cache-size and l2-cache-size are given, the part of
the cache-size that is not used for the L2 cache yet."?
That is not accurate. Because even if l2-cache-size is not given and
cache-size is large enough to accommodate enough L2 cache to cover the
entire image, plus the minimal amount of refcount cache with room to
spare - refcount cache will use all the rest of the cache-size. How about:
"default: 4 times the cluster size; or if cache-size is specified, the
part of it which is not used for the L2 cache"
Leonid.
Kevin
