linux-kernel - Re: [PATCH 02/10] x86: Change size of node ids from u8 to u16 V3

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Message-Id: <20080116185356.e8d02344.dada1@cosmosbay.com>
Date:	Wed, 16 Jan 2008 18:53:56 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	travis@....com
Cc:	Andrew Morton <akpm@...ux-foundation.org>, Andi Kleen <ak@...e.de>,
	mingo@...e.hu, Christoph Lameter <clameter@....com>,
	Jack Steiner <steiner@....com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/10] x86: Change size of node ids from u8 to u16 V3

On Wed, 16 Jan 2008 09:09:04 -0800
travis@....com wrote:

> Change the size of node ids from 8 bits to 16 bits to
> accomodate more than 256 nodes.
> 
> Signed-off-by: Mike Travis <travis@....com>
> Reviewed-by: Christoph Lameter <clameter@....com>
> ---
> V1->V2:
>     - changed pxm_to_node_map to u16
>     - changed memnode map entries to u16
> V2->V3:
>     - changed memnode.embedded_map from [64-16] to [64-8]
>       (and size comment to 128 bytes)
> ---
>  arch/x86/mm/numa_64.c       |    9 ++++++---
>  arch/x86/mm/srat_64.c       |    2 +-
>  drivers/acpi/numa.c         |    2 +-
>  include/asm-x86/mmzone_64.h |    6 +++---
>  include/asm-x86/numa_64.h   |    4 ++--
>  include/asm-x86/topology.h  |    2 +-
>  6 files changed, 14 insertions(+), 11 deletions(-)

I know new typedefs are not welcome, but in this case, it could be nice
to define a fundamental type node_t (like pte_t, pmd_t, pgd_t, ...).

Clean NUMA code deserves it. 

#if MAX_NUMNODES > 256
typedef u16 node_t;
#else
typedef u8 node_t;
#endif

In 2016, we can add u32 for MAX_NUMNODES > 65536

Another point: you want this change, sorry if my previous mail was not detailed enough :

--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -78,7 +78,7 @@ static int __init allocate_cachealigned_memnodemap(void)
        unsigned long pad, pad_addr;
 
        memnodemap = memnode.embedded_map;
-       if (memnodemapsize <= 48)
+       if (memnodemapsize <= ARRAY_SIZE(memnode.embedded_map))
                return 0;
 
        pad = L1_CACHE_BYTES - 1;


Thanks
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