linux-kernel - Re: [PATCH 3/4] PM/Hibernate: Use memory allocations to free memory (rev. 2)

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Date:	Sun, 3 May 2009 11:36:59 +0200
From:	Pavel Machek <pavel@....cz>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	jens.axboe@...cle.com, alan-jenkins@...fmail.co.uk,
	linux-kernel@...r.kernel.org, kernel-testers@...r.kernel.org,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH 3/4] PM/Hibernate: Use memory allocations to free
	memory (rev. 2)

Hi!

> > Remove the shrinking of memory from the suspend-to-RAM code, where it is 
> > not really necessary.
> 
> Hmm. Shouldn't we do this _regardless_?
> 
> IOW, shouldn't this be a totally separate patch? It seems to be left-over 
> from when we shared the same code-paths, and before the split of the STR 
> and hibernate code?
> 
> IOW, shouldn't the very _first_ patch just be this part? That code doesn't 
> make any sense anyway (that FREE_PAGE_NUMBER really _is_ totally 
> arbitrary).
> 
> This part seems to be totally independent of all the other parts in your 
> patch-series. No?

I'm not sure this one is a good idea: drivers will need to allocate
memory during suspend/resume, and when processes are frozen/disk
driver is suspended, normal memory management will no longer work.

So, freeing 4M of memory before starting suspend seems like a good
idea. That way those small alocations will not fail.
								Pavel


> @@ -188,9 +188,6 @@ static void suspend_test_finish(const char *label)
>  
>  #endif
>  
> -/* This is just an arbitrary number */
> -#define FREE_PAGE_NUMBER (100)
> -
>  static struct platform_suspend_ops *suspend_ops;
>  
>  /**
> @@ -241,24 +238,10 @@ static int suspend_prepare(void)
>  	if (error)
>  		goto Finish;
>  
> -	if (suspend_freeze_processes()) {
> -		error = -EAGAIN;
> -		goto Thaw;
> -	}
> -
> -	free_pages = global_page_state(NR_FREE_PAGES);
> -	if (free_pages < FREE_PAGE_NUMBER) {
> -		pr_debug("PM: free some memory\n");
> -		shrink_all_memory(FREE_PAGE_NUMBER - free_pages);
> -		if (nr_free_pages() < FREE_PAGE_NUMBER) {
> -			error = -ENOMEM;
> -			printk(KERN_ERR "PM: No enough memory\n");
> -		}
> -	}
> +	error = suspend_freeze_processes();
>  	if (!error)
>  		return 0;
>  
> - Thaw:
>  	suspend_thaw_processes();
>  	usermodehelper_enable();
>   Finish:

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