netdev - Re: [PATCH v8 net-next 5/7] net: simple poll/select low latency socket poll

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Message-ID: <51ACA15C.4060101@linux.intel.com>
Date:	Mon, 03 Jun 2013 16:59:56 +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>,
	Alex Rosenbaum <alexr@...lanox.com>,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH v8 net-next 5/7] net: simple poll/select low latency socket
 poll

On 03/06/2013 16:15, Eric Dumazet wrote:
> On Mon, 2013-06-03 at 11:02 +0300, Eliezer Tamir wrote:
>>   	sock = file->private_data;
>> -	return sock->ops->poll(file, sock, wait);
>> +
>> +	poll_result = sock->ops->poll(file, sock, wait);
>> +
>> +	if (!(poll_result & (POLLRDNORM | POLLERR | POLLRDHUP | POLLHUP)) &&
>> +		sk_valid_ll(sock->sk) && sk_poll_ll(sock->sk, 1))
>> +			poll_result = sock->ops->poll(file, sock, NULL);
>> +
>> +	return poll_result;
>>   }
>>
>>   static int sock_mmap(struct file *file, struct vm_area_struct *vma)
>>
>
>
> In fact, for TCP, POLLOUT event being ready can also be triggered by
> incoming messages, as the ACK might allow the user application to push
> more data in the write queue.
>
> And you might check wait->_key to avoid testing flags that user is not
> interested into.

yes, comparing to _key is more correct.
In any case this needs to be completely rewritten for support for
working well with a large number of sockets.

-Eliezer
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