[pulseaudio-discuss] [PATCH 2/2] pstream: Optimise read of smaller packages

[David Henningsson]

On 04/10/2013 02:07 PM, Tanu Kaskinen wrote:
> On Wed, 2013-04-10 at 08:50 +0200, David Henningsson wrote:
>> On 04/08/2013 06:27 PM, Tanu Kaskinen wrote:
>>> On Sun, 2013-04-07 at 11:59 +0200, David Henningsson wrote:
>>> I also have some reservations about using goto to backwards in a complex
>>> function. I'm not sure, however, that using a proper loop structure
>>> would make the code any more readable. Splitting the function into
>>> smaller functions is something to consider, but I'm not demanding that
>>> if you don't think it's a good idea.
>>>
>>
>> For the record, I've pushed the write patch to both branches now.
>>
>> I'm having second thoughts about the read patch. Perhaps it's better to
>> introduce an extra layer of buffering instead? E g, pa_iochannel_read
>> would then never call pa_read with anything less than, say, 256 bytes.
>> (For big reads, there would still be no memory copy.)
>
> Reading always at least 256 bytes at a time sounds like a good idea, but
> I don't immediately see how it would work in practice. Just adding some
> buffering in the iochannel doesn't help much. It may save a read()
> syscall (if libc doesn't already do some extra buffering), but if
> do_read() isn't modified in any way, the extra ppoll() call will still
> be there.
>

Right, do_pstream_read_write would then have a
   while iochannel_is_readable()
     do_read();

...and the readable flag is not cleared as long as there is something in 
the intermediate buffer.

-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic