From: Andi Kleen <andi@firstfloor.org>
Subject: Re: [PATCH v4 net-next] net: poll/select low latency
	socket support
Date: Fri, 28 Jun 2013 06:43:05 +0200
Message-ID: <20130628044305.GQ6123@two.firstfloor.org>
References: <20130624072751.26134.78163.stgit@ladj378.jer.intel.com>
	<20130624072803.26134.41593.stgit@ladj378.jer.intel.com>
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Cc: Willem de Bruijn <willemb@google.com>, Or Gerlitz <or.gerlitz@gmail.com>,
	e1000-devel@lists.sourceforge.net, netdev@vger.kernel.org,
	HPA <hpa@zytor.com>, Amir Vadai <amirv@mellanox.com>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Alex Rosenbaum <alexr@mellanox.com>, linux-kernel@vger.kernel.org,
	Eliezer Tamir <eliezer@tamir.org.il>, Andi Kleen <andi@firstfloor.org>,
	Ben Hutchings <bhutchings@solarflare.com>,
	Eric Dumazet <erdnetdev@gmail.com>, Eilon Greenstien <eilong@broadcom.com>,
	David Miller <davem@davemloft.net>
To: Eliezer Tamir <eliezer.tamir@linux.intel.com>
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In-Reply-To: <20130624072803.26134.41593.stgit@ladj378.jer.intel.com>
Errors-To: e1000-devel-bounces@lists.sourceforge.net

> @@ -400,6 +402,8 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
>  	poll_table *wait;
>  	int retval, i, timed_out = 0;
>  	unsigned long slack = 0;
> +	unsigned int ll_flag = POLL_LL;
> +	u64 ll_time = ll_end_time();

So you're adding a sched_clock to every select call, even if it has
nothing to do with ll? 

That seems rather drastic. select can be performance critical.

-andi

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