linux-kernel - Re: [PATCH v9 net-next 5/7] net: simple poll/select low latency socket poll

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Date:	Wed, 05 Jun 2013 17:56:19 +0300
From:	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	David Miller <davem@...emloft.net>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	e1000-devel@...ts.sourceforge.net,
	Willem de Bruijn <willemb@...gle.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Andi Kleen <andi@...stfloor.org>, HPA <hpa@...or.com>,
	Eilon Greenstien <eilong@...adcom.com>,
	Or Gerlitz <or.gerlitz@...il.com>,
	Amir Vadai <amirv@...lanox.com>,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH v9 net-next 5/7] net: simple poll/select low latency socket
 poll

On 05/06/2013 17:17, Eric Dumazet wrote:
> On Wed, 2013-06-05 at 06:56 -0700, Eric Dumazet wrote:
>
>> This looks quite easy, by adding in include/uapi/asm-generic/poll.h
>>
>> #define POLL_LL 0x8000
>>
>> And do the sk_poll_ll() call only if flag is set.
>>
>> I do not think we have to support select(), as its legacy interface, and
>> people wanting ll should really use epoll() or poll().
>
> Alternatively, add a per socket flag to enable/disable ll
>
> This global enable assumes the application owns the host anyway.
>

I plan on adding a socket option in the next stage.
I'm also testing a patch much like you described with a poll flag.
Select/poll set it to indicate that they want to busy poll.
Sock_poll sets it to indicate that this socket can (at the moment)
busy-poll.

If you think the way things are done right now is unacceptable,
even as an experimental feature, I would much prefer to drop this patch
and have the rest applied rather then bring in new code that is not 
fully tested at this stage.

-Eliezer

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