linux-kernel - Re: [PATCH 2/2][v2] powerpc: Make the CMM memory hotplug aware

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Message-ID: <4ACDD71D.30809@linux.vnet.ibm.com>
Date:	Thu, 08 Oct 2009 14:12:13 +0200
From:	Gerald Schaefer <geralds@...ux.vnet.ibm.com>
To:	Robert Jennings <rcj@...ux.vnet.ibm.com>
CC:	Mel Gorman <mel@....ul.ie>, Ingo Molnar <mingo@...e.hu>,
	Badari Pulavarty <pbadari@...ibm.com>,
	Brian King <brking@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linuxppc-dev@...abs.org
Subject: Re: [PATCH 2/2][v2] powerpc: Make the CMM memory hotplug aware

Hi,

I am currently working on the s390 port for the cmm + hotplug
patch, and I'm a little confused about the memory allocation
policy, see below. Is it correct that the balloon cannot grow
into ZONE_MOVABLE, while the pages for the balloon page list
can?

Robert Jennings wrote:
> @@ -110,6 +125,9 @@ static long cmm_alloc_pages(long nr)
>  	cmm_dbg("Begin request for %ld pages\n", nr);
> 
>  	while (nr) {
> +		if (atomic_read(&hotplug_active))
> +			break;
> +
>  		addr = __get_free_page(GFP_NOIO | __GFP_NOWARN |
>  				       __GFP_NORETRY | __GFP_NOMEMALLOC);
>  		if (!addr)
> @@ -119,8 +137,10 @@ static long cmm_alloc_pages(long nr)
>  		if (!pa || pa->index >= CMM_NR_PAGES) {
>  			/* Need a new page for the page list. */
>  			spin_unlock(&cmm_lock);
> -			npa = (struct cmm_page_array *)__get_free_page(GFP_NOIO | __GFP_NOWARN |
> -								       __GFP_NORETRY | __GFP_NOMEMALLOC);
> +			npa = (struct cmm_page_array *)__get_free_page(
> +					GFP_NOIO | __GFP_NOWARN |
> +					__GFP_NORETRY | __GFP_NOMEMALLOC |
> +					__GFP_MOVABLE);
>  			if (!npa) {
>  				pr_info("%s: Can not allocate new page list\n", __func__);
>  				free_page(addr);

Why is the __GFP_MOVABLE added here, for the page list alloc, and not
above for the balloon page alloc?

--
Regards,
Gerald

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