Signed-off-by: Leonid Bloch <lbloch@janustech.com>
---
 docs/qcow2-cache.txt |  9 ++++++---
 qapi/block-core.json |  6 +++---
 qemu-options.hx      | 15 +++++++++------
 3 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/docs/qcow2-cache.txt b/docs/qcow2-cache.txt
index 8a09a5cc5f..fd9a6911cc 100644
--- a/docs/qcow2-cache.txt
+++ b/docs/qcow2-cache.txt
@@ -112,9 +112,9 @@ command-line, or the 'blockdev-add' QMP command.
 
 There are three options available, and all of them take bytes:
 
-"l2-cache-size":         maximum size of the L2 table cache
-"refcount-cache-size":   maximum size of the refcount block cache
-"cache-size":            maximum size of both caches combined
+"l2-cache-size":         maximal size of the L2 table cache
+"refcount-cache-size":   maximal size of the refcount block cache
+"cache-size":            maximal size of both caches combined
 
 There are a few things that need to be taken into account:
 
@@ -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.
+
 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/qapi/block-core.json b/qapi/block-core.json
index d40d5ecc3b..22f85687df 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2808,10 +2808,10 @@
 # @overlap-check:         which overlap checks to perform for writes
 #                         to the image, defaults to 'cached' (since 2.2)
 #
-# @cache-size:            the maximum total size of the L2 table and
+# @cache-size:            the maximal total size of the L2 table and
 #                         refcount block caches in bytes (since 2.2)
 #
-# @l2-cache-size:         the maximum size of the L2 table cache in
+# @l2-cache-size:         the maximal size of the L2 table cache in
 #                         bytes (since 2.2)
 #
 # @l2-cache-entry-size:   the size of each entry in the L2 cache in
@@ -2819,7 +2819,7 @@
 #                         and the cluster size. The default value is
 #                         the cluster size (since 2.12)
 #
-# @refcount-cache-size:   the maximum size of the refcount block cache
+# @refcount-cache-size:   the maximal size of the refcount block cache
 #                         in bytes (since 2.2)
 #
 # @cache-clean-interval:  clean unused entries in the L2 and refcount
diff --git a/qemu-options.hx b/qemu-options.hx
index b1bf0f485f..18f3f87da5 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -751,16 +751,19 @@ Whether to enable the lazy refcounts feature (on/off; default is taken from the
 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)
+The maximal total size of the L2 table and refcount block caches in bytes
+(default: the sum of l2-cache-size and refcount-cache-size)
 
 @item l2-cache-size
-The maximum size of the L2 table cache in bytes
-(default: 4/5 of the total cache size)
+The maximal size of the L2 table cache in bytes
+(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)
+The maximal size of the refcount block cache in bytes
+(default: 4 times the cluster size; or if cache-size is specified, the part of
+it which is not used for the L2 cache)
 
 @item cache-clean-interval
 Clean unused entries in the L2 and refcount caches. The interval is in seconds.
-- 
2.17.1

On Sun 29 Jul 2018 11:27:41 PM CEST, Leonid Bloch wrote:
> Signed-off-by: Leonid Bloch <lbloch@janustech.com>
> ---
>  docs/qcow2-cache.txt |  9 ++++++---
>  qapi/block-core.json |  6 +++---
>  qemu-options.hx      | 15 +++++++++------
>  3 files changed, 18 insertions(+), 12 deletions(-)
>
> diff --git a/docs/qcow2-cache.txt b/docs/qcow2-cache.txt
> index 8a09a5cc5f..fd9a6911cc 100644
> --- a/docs/qcow2-cache.txt
> +++ b/docs/qcow2-cache.txt
> @@ -112,9 +112,9 @@ command-line, or the 'blockdev-add' QMP command.
>  
>  There are three options available, and all of them take bytes:
>  
> -"l2-cache-size":         maximum size of the L2 table cache
> -"refcount-cache-size":   maximum size of the refcount block cache
> -"cache-size":            maximum size of both caches combined
> +"l2-cache-size":         maximal size of the L2 table cache
> +"refcount-cache-size":   maximal size of the refcount block cache
> +"cache-size":            maximal size of both caches combined

Why is 'maximum' not clear in this context?

Otherwise the patch looks good to me.

Berto

On 08/03/2018 02:27 PM, Alberto Garcia wrote:
> On Sun 29 Jul 2018 11:27:41 PM CEST, Leonid Bloch wrote:
>> Signed-off-by: Leonid Bloch <lbloch@janustech.com>
>> ---
>>   docs/qcow2-cache.txt |  9 ++++++---
>>   qapi/block-core.json |  6 +++---
>>   qemu-options.hx      | 15 +++++++++------
>>   3 files changed, 18 insertions(+), 12 deletions(-)
>>
>> diff --git a/docs/qcow2-cache.txt b/docs/qcow2-cache.txt
>> index 8a09a5cc5f..fd9a6911cc 100644
>> --- a/docs/qcow2-cache.txt
>> +++ b/docs/qcow2-cache.txt
>> @@ -112,9 +112,9 @@ command-line, or the 'blockdev-add' QMP command.
>>   
>>   There are three options available, and all of them take bytes:
>>   
>> -"l2-cache-size":         maximum size of the L2 table cache
>> -"refcount-cache-size":   maximum size of the refcount block cache
>> -"cache-size":            maximum size of both caches combined
>> +"l2-cache-size":         maximal size of the L2 table cache
>> +"refcount-cache-size":   maximal size of the refcount block cache
>> +"cache-size":            maximal size of both caches combined
> 
> Why is 'maximum' not clear in this context?

It seemed to me that it is grammatically incorrect, because maximum is a 
noun and maximal is an adjective. But after a quick check now I see that 
maximum can be used as an adjective as well, so indeed this change is 
not needed. Will update in the next version.

Thanks,
Leonid.

> 
> Otherwise the patch looks good to me.
> 
> Berto
>