linux-kernel - Re: [patch] snd hda suspend latency: shorten codec read

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Date:	Fri, 16 Nov 2007 14:31:39 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Mark Lord <lkml@....ca>, perex@...ex.cz,
	Takashi Iwai <tiwai@...e.de>, Pavel Machek <pavel@....cz>,
	Mark Lord <liml@....ca>, Thomas Gleixner <tglx@...utronix.de>,
	len.brown@...el.com, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Len Brown <lenb@...nel.org>
Subject: Re: [patch] snd hda suspend latency: shorten codec read

On Friday, 16 of November 2007, Ingo Molnar wrote:
> 
> snd hda suspend latency goes down a second via the patch below.
> 
> 	Ingo
> 
> ------------->
> Subject: snd hda suspend latency: shorten codec read
> From: Ingo Molnar <mingo@...e.hu>
> 
> not sleeping for every codec read/write but doing a short udelay and
> a conditional reschedule has cut suspend+resume latency by about 1
> second on my T60.
> 
> Signed-off-by: Ingo Molnar <mingo@...e.hu>

Acked-by: Rafael J. Wysocki <rjw@...k.pl>

> ---
>  sound/pci/hda/hda_intel.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> Index: linux/sound/pci/hda/hda_intel.c
> ===================================================================
> --- linux.orig/sound/pci/hda/hda_intel.c
> +++ linux/sound/pci/hda/hda_intel.c
> @@ -555,7 +555,8 @@ static unsigned int azx_rirb_get_respons
>  		}
>  		if (!chip->rirb.cmds)
>  			return chip->rirb.res; /* the last value */
> -		schedule_timeout_uninterruptible(1);
> +		udelay(10);
> +		cond_resched();
>  	} while (time_after_eq(timeout, jiffies));
>  
>  	if (chip->msi) {
> 
> 



-- 
"Premature optimization is the root of all evil." - Donald Knuth
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