From: Christoph Lameter <cl@linux.com>
To: David Rientjes <rientjes@google.com>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>,
Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>,
linux-mm@kvack.org, "David S. Miller" <davem@davemloft.net>,
netfilter@vger.kernel.org, Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [PATCH] slob: push the min alignment to long long
Date: Thu, 23 Jun 2011 09:36:12 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1106230934250.19668@router.home> (raw)
In-Reply-To: <alpine.DEB.2.00.1106221641120.14635@chino.kir.corp.google.com>
On Wed, 22 Jun 2011, David Rientjes wrote:
> > * struct kmem_cache
> > *
> > * manages a cache.
>
> Looks like we lost some valuable information in the comments when this got
> moved to slab.h :(
Ok. If we want a description for these defines then lets use this.
Subject: slab allocators: Provide generic description of alignment defines
Provide description for alignment defines.
Signed-off-by: Christoph Lameter <cl@linux.com>
---
include/linux/slab.h | 10 ++++++++++
1 file changed, 10 insertions(+)
Index: linux-2.6/include/linux/slab.h
===================================================================
--- linux-2.6.orig/include/linux/slab.h 2011-06-23 09:26:55.000000000 -0500
+++ linux-2.6/include/linux/slab.h 2011-06-23 09:33:46.000000000 -0500
@@ -133,12 +133,22 @@ unsigned int kmem_cache_size(struct kmem
#define KMALLOC_MAX_SIZE (1UL << KMALLOC_SHIFT_HIGH)
#define KMALLOC_MAX_ORDER (KMALLOC_SHIFT_HIGH - PAGE_SHIFT)
+/*
+ * Some archs want to perform DMA into kmalloc caches and need a guaranteed
+ * alignment larger than the alignment of a 64-bit integer.
+ * Setting ARCH_KMALLOC_MINALIGN in arch headers allows that.
+ */
#ifdef ARCH_DMA_MINALIGN
#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
#else
#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
#endif
+/*
+ * Setting ARCH_SLAB_MINALIGN in arch headers allows a different alignment.
+ * Intended for arches that get misalignment faults even for 64 bit integer
+ * aligned buffers.
+ */
#ifndef ARCH_SLAB_MINALIGN
#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
#endif
--
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next prev parent reply other threads:[~2011-06-23 14:36 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-14 20:10 Sebastian Andrzej Siewior
2011-06-14 20:40 ` Christoph Lameter
2011-06-14 21:16 ` Christoph Lameter
2011-06-15 20:06 ` Sebastian Andrzej Siewior
2011-06-16 16:48 ` Pekka Enberg
2011-06-22 23:41 ` David Rientjes
2011-06-23 14:36 ` Christoph Lameter [this message]
2011-06-23 20:24 ` David Rientjes
2011-06-14 22:05 ` Matt Mackall
2011-06-15 20:12 ` Sebastian Andrzej Siewior
2011-06-15 20:24 ` Matt Mackall
2011-06-15 20:40 ` Pekka Enberg
2011-06-15 20:55 ` Matt Mackall
2011-06-15 22:11 ` David Miller
2011-06-15 22:53 ` Matt Mackall
2011-06-16 6:59 ` Pekka Enberg
2011-06-16 15:23 ` Matt Mackall
2011-06-16 15:28 ` Pekka Enberg
2011-06-15 22:08 ` David Miller
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