Re: [PATCH 9/9] qemu-file: Account for rate_limit usage on qemu_fflush()

[Juan Quintela <quintela@redhat.com>]

Peter Xu <peterx@redhat.com> wrote:
> On Thu, May 04, 2023 at 01:38:41PM +0200, Juan Quintela wrote:
>> That is the moment we know we have transferred something.
>> 
>> Signed-off-by: Juan Quintela <quintela@redhat.com>
>
> There'll be a slight side effect that qemu_file_rate_limit() can be
> triggered later than before because data cached in the qemufile won't be
> accounted until flushed.
>
> Two limits here:
>
> - IO_BUF_SIZE==32K, the real buffer
> - MAX_IOV_SIZE==64 (I think), the async buffer to put guest page ptrs
>   directly, on x86 it's 64*4K=256K
>
> So the impact should be no more than 288KB on x86.  Looks still fine..

This was on purpose.  We are counting data as sent when it has not been
sent yet.

With this change, we account for the data written when we do the real
write.

And yes, I fully agree that with the size that we have it shouldn't make
much of a difference in the speed calculation.

The difference here is that I will move that counter somewhere else, and
the less places that I have to use it the better O:-)

> Reviewed-by: Peter Xu <peterx@redhat.com>

Thanks.