Re: [Qemu-devel] [PATCH] RFC: qio: Improve corking of TLS sessions

[Eric Blake]

On 6/10/19 9:02 AM, Eric Blake wrote:

> 
> send(MSG_MORE)
> send()
> 
> is ideal; under the hood, we can translate it to:
> 
> send(MSG_MORE)
>   gnutls_record_cork()
>   gnutls_record_send()
> send()
>   if (size > threshold) {
>     gnutls_record_uncork()
>     gnutls_record_send()
>   } else {
>     gnutls_record_send()
>     gnutls_record_uncork()
>   }
> 
> So we really need a way to plumb a MSG_MORE flag for senders to use,
> when they KNOW they will be sending back-to-back pieces and where the
> first piece is short, but it is not yet obvious whether the second piece
> is short or long.

This is what I meant to say,

> 
> MSG_MORE was lon the next message to go through the stack, if the
> previous message next paccork for

this was an editing accident on incomplete thoughts.  But I wanted to add:

Setting up the ability to pass MGS_MORE through the qio stack will
require either an update to ALL callers of qio_write to pass a flags
argument (usually 0), or to add a set of new entry points to qio for the
few callers that want to pass a non-zero flags argument (for now, nbd
and sheepdog).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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