linux-kernel - Re: [v3 9/9] s390: teach platforms not to zero struct pages memory

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Date:   Mon, 8 May 2017 13:36:24 +0200
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
Cc:     linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, borntraeger@...ibm.com,
        davem@...emloft.net
Subject: Re: [v3 9/9] s390: teach platforms not to zero struct pages memory

On Fri, May 05, 2017 at 01:03:16PM -0400, Pavel Tatashin wrote:
> If we are using deferred struct page initialization feature, most of
> "struct page"es are getting initialized after other CPUs are started, and
> hence we are benefiting from doing this job in parallel. However, we are
> still zeroing all the memory that is allocated for "struct pages" using the
> boot CPU.  This patch solves this problem, by deferring zeroing "struct
> pages" to only when they are initialized on s390 platforms.
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
> Reviewed-by: Shannon Nelson <shannon.nelson@...cle.com>
> ---
>  arch/s390/mm/vmem.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
> index 9c75214..ffe9ba1 100644
> --- a/arch/s390/mm/vmem.c
> +++ b/arch/s390/mm/vmem.c
> @@ -252,7 +252,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
>  				void *new_page;
>  
>  				new_page = vmemmap_alloc_block(PMD_SIZE, node,
> -							       true);
> +							       VMEMMAP_ZERO);
>  				if (!new_page)
>  					goto out;
>  				pmd_val(*pm_dir) = __pa(new_page) | sgt_prot;

If you add the hunk below then this is

Acked-by: Heiko Carstens <heiko.carstens@...ibm.com>

diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index ffe9ba1aec8b..bf88a8b9c24d 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -272,7 +272,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 		if (pte_none(*pt_dir)) {
 			void *new_page;
 
-			new_page = vmemmap_alloc_block(PAGE_SIZE, node, true);
+			new_page = vmemmap_alloc_block(PAGE_SIZE, node, VMEMMAP_ZERO);
 			if (!new_page)
 				goto out;
 			pte_val(*pt_dir) = __pa(new_page) | pgt_prot;