linux-kernel - Re: [PATCH] PM / Hiberante : optimize swsusp

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Date:	Thu, 19 Mar 2015 09:54:48 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Tom(JeHyeon) Yeon" <tomyeon750415lkml@...il.com>
Cc:	len.brown@...el.com, jroedel@...e.de, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Tom(JeHyeon) Yeon" <tom.yeon@...driver.com>
Subject: Re: [PATCH] PM / Hiberante : optimize swsusp_free()

On Thu 2015-03-19 17:28:58, Tom(JeHyeon) Yeon wrote:
> From: "Tom(JeHyeon) Yeon" <tom.yeon@...driver.com>
> 
> I tested the performance of swsusp_free operation.
> The free time took about 58768us before commit fdd64ed, and
> the free time took about 40535us after the commit fdd64ed.
> 
> But, I optimized the function before I saw commit fdd64ed.
> So, I applied the patch in my system.(ARM Coretex A9, Dual Core 1GHz)
> The free time took about 35164us.
> I think that the finding routine for the same pfn is redundant
> 
> Signed-off-by: Tom(JeHyeon) Yeon <tom.yeon@...driver.com>

Well, saving 5msec on operation that takes 30 seconds is not that
much, but new code looks cleaner.

Acked-by: Pavel Machek <pavel@....cz>

> @@ -726,14 +726,6 @@ static void memory_bm_clear_bit(struct memory_bitmap *bm, unsigned long pfn)
>  	clear_bit(bit, addr);
>  }
>  
> -static void memory_bm_clear_current(struct memory_bitmap *bm)
> -{
> -	int bit;
> -
> -	bit = max(bm->cur.node_bit - 1, 0);
> -	clear_bit(bit, bm->cur.node->data);
> -}
> -
>  static int memory_bm_test_bit(struct memory_bitmap *bm, unsigned long pfn)
>  {
>  	void *addr;
> @@ -1342,36 +1334,21 @@ static struct memory_bitmap copy_bm;
>  
>  void swsusp_free(void)
>  {
> -	unsigned long fb_pfn, fr_pfn;
> +	unsigned long pfn;
>  
>  	if (!forbidden_pages_map || !free_pages_map)
>  		goto out;
>  
>  	memory_bm_position_reset(forbidden_pages_map);
> -	memory_bm_position_reset(free_pages_map);
> -
> -loop:
> -	fr_pfn = memory_bm_next_pfn(free_pages_map);
> -	fb_pfn = memory_bm_next_pfn(forbidden_pages_map);
> -
> -	/*
> -	 * Find the next bit set in both bitmaps. This is guaranteed to
> -	 * terminate when fb_pfn == fr_pfn == BM_END_OF_MAP.
> -	 */
> -	do {
> -		if (fb_pfn < fr_pfn)
> -			fb_pfn = memory_bm_next_pfn(forbidden_pages_map);
> -		if (fr_pfn < fb_pfn)
> -			fr_pfn = memory_bm_next_pfn(free_pages_map);
> -	} while (fb_pfn != fr_pfn);
> -
> -	if (fr_pfn != BM_END_OF_MAP && pfn_valid(fr_pfn)) {
> -		struct page *page = pfn_to_page(fr_pfn);
> -
> -		memory_bm_clear_current(forbidden_pages_map);
> -		memory_bm_clear_current(free_pages_map);
> -		__free_page(page);
> -		goto loop;
> +	for ( ; ; ) {
> +		pfn  = memory_bm_next_pfn(forbidden_pages_map);
> +		if (BM_END_OF_MAP == pfn)
> +			break;
> +		if (memory_bm_test_bit(free_pages_map, pfn)) {
> +			memory_bm_clear_bit(forbidden_pages_map, pfn);
> +			memory_bm_clear_bit(free_pages_map, pfn);
> +			__free_page(pfn_to_page(pfn));
> +		}
>  	}
>  
>  out:

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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