netdev - Re: [PATCH 1/2] rtlwifi: Fix improve function 'rtl_addr

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Message-ID: <56B371BE.1060805@lwfinger.net>
Date:	Thu, 4 Feb 2016 09:43:58 -0600
From:	Larry Finger <Larry.Finger@...inger.net>
To:	David Laight <David.Laight@...LAB.COM>,
	ByeoungWook Kim <quddnr145@...il.com>
Cc:	"kvalo@...eaurora.org" <kvalo@...eaurora.org>,
	"chaoming_li@...lsil.com.cn" <chaoming_li@...lsil.com.cn>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] rtlwifi: Fix improve function 'rtl_addr_delay()' in
 core.c

On 02/04/2016 03:48 AM, David Laight wrote:
> From: Larry Finger
>> Sent: 03 February 2016 19:45
> ...
>> The performance will depend on where you satisfy the condition. All switch cases
>> have the same execution time, but in the if .. else if .. else form, the earlier
>> tests execute more quickly. I'm not sure that one can make any blanket statement
>> about performance. Certainly, the switch version will be larger. For a switch
>> with 8 cases plus default, the object code if 43 bytes larger than the nested
>> ifs in a test program that I created. That is a significant penalty.
>
> There is also the penalty of the (likely) data cache miss reading the jump table.
> But given this code is all about generating a variable delay the execution
> speed is probably irrelevant.
>
> It would be much more interesting if the delay could be changed for sleeps.

Unfortunately, sleeping is not possible for the routines that call rtl_addr_delay().

Larry