linux-kernel - Re: [PATCH v4 net-next] net: poll/select low latency socket support

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Message-ID: <20130628044305.GQ6123@two.firstfloor.org>
Date:	Fri, 28 Jun 2013 06:43:05 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Eliezer Tamir <eliezer.tamir@...ux.intel.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>,
	Eric Dumazet <erdnetdev@...il.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>,
	Alex Rosenbaum <alexr@...lanox.com>,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH v4 net-next] net: poll/select low latency socket support

> @@ -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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