linux-kernel - Re: [PATCH v9 net-next 2/7] net: add low latency socket poll

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Date:	Wed, 05 Jun 2013 18:46:34 +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 2/7] net: add low latency socket poll

On 05/06/2013 18:39, Eric Dumazet wrote:
> On Wed, 2013-06-05 at 18:30 +0300, Eliezer Tamir wrote:
>> On 05/06/2013 18:21, Eric Dumazet wrote:

>>> It would also make sense to give end_time as a parameter, so that the
>>> polling() code could really give  a end_time for the whole duration of
>>> poll().
>>>
>>> (You then should test can_poll_ll(end_time) _before_ call to
>>> ndo_ll_poll())
>>
>> how would you handle a nonblocking operation in that case?
>> I guess if we have a socket option, then we don't need to handle none
>> blocking any diffrent, since the user specified exactly how much time to
>> waste polling. right?
>
> If the thread already spent 50us in the poll() system call, it for sure
> should not call any ndo_ll_poll(). This makes no more sense at this
> point.

what about a non-blocking read from a socket?
Right now we assume this means poll only once since the application will 
repeat as needed.

maybe add a "once" parameter that will cause sk_poll_ll() to ignore end 
time and only try once?
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