Re: [hybi] frame length encoding

["Shelby Moore" <[e-mail]>]

> On Sat, 2010-08-21 at 15:54 -0400, Shelby Moore wrote:
>
>>
>> No because for any file on disk larger than 4GB, we will have to move
>> the
>> entire file through the CPU, when we wouldn't had to otherwise:
>>
>
> there seems to be a misunderstanding about ZC techniques here. To be
> efficient they certainly require a large-ish chunk size, but there is no
> all-or-nothing requirement like you assert that would require copying
> through the CPU to only send a subset of the data.
>
> 32 bits with chunking would be fine to accommodate zero copy.

My understanding is there would be copying, if you read my link again
carefully:

http://www.ietf.org/mail-archive/web/hybi/current/msg03402.html

The reason is because I understand from what I read at John's links that
the entire file is contiguous in memory (because it is a memory mapped or
memory cached copy of the file on the disk), and thus to insert the frame
headers at the 32bit chunks, you would have to move the entire file
through the CPU.  Is my understanding incorrect?  Can you simply rewrite
one sector on disk and the memory manager remaps?

>
> there are some folks that want to be able to send any message in one
> chunk for unrelated reasons.