Re: [Xen-devel] [PATCH 4 of 4 v3] blkif.h: Define and document the request number/size/segments extension

["Justin T. Gibbs" <justing@xxxxxxxxxxxxxxxx>]

On Feb 21, 2012, at 7:38 AM, Ian Campbell wrote:

> On Mon, 2012-02-20 at 18:07 +0000, Justin T. Gibbs wrote:
>> Note: As of __XEN_INTERFACE_VERSION__ 0x00040201 the definition of
>>      BLKIF_MAX_SEGMENTS_PER_REQUEST has changed.  Drivers must be updated
>>      to, at minimum, use BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK, before being
>>      recompiled with a __XEN_INTERFACE_VERSION greater than or equal to
>>      this value.
>> 
>> This extension first appeared in the FreeBSD Operating System.
>> 
>> Signed-off-by: Justin T. Gibbs <justing@xxxxxxxxxxxxxxxx>
>> 
>> diff -r 09051133e2fe -r a777cbc5f48b xen/include/public/io/blkif.h
>> --- a/xen/include/public/io/blkif.h  Mon Feb 20 11:02:53 2012 -0700
>> +++ b/xen/include/public/io/blkif.h  Mon Feb 20 11:03:01 2012 -0700
>> @@ -145,6 +145,32 @@
>>  *      The maximum supported size of the request ring buffer in units of
>>  *      machine pages.  The value must be a power of 2.
>>  *
>> + * max-requests         <uint32_t>
>> + *      Default Value:  BLKIF_MAX_RING_REQUESTS(PAGE_SIZE)
>> + *      Maximum Value:  BLKIF_MAX_RING_REQUESTS(PAGE_SIZE * max-ring-pages)
>> + *
>> + *      The maximum number of concurrent, logical requests that will be
>> + *      issued by the backend.
> 
> by "issued" do you mean the maximum number that the backend is willing
> to consume/have-in-flight at once? I guess that means issued to the
> underlying storage? (backend doesn't issue requests to the frontend does
> it? That's how I first read it, hence my question)
> 
> Ian.
> 

I should have used the same language as in the other entries.  Does this
make more sense?

 *      The maximum number of concurrent, logical requests supported by
 *      the backend.

--
Justin
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