From: David Howells <dhowells@redhat.com>
To: torvalds@osdl.org, mingo@elte.hu, tglx@linutronix.de,
matthew@wil.cx, arjan@infradead.org
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
David Howells <dhowells@redhat.com>
Subject: [PATCH 2/3] Adjust the comment on get_order() to describe the size==0 case [ver #2]
Date: Sat, 17 Apr 2010 15:07:06 +0100 [thread overview]
Message-ID: <20100417140706.15855.78347.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <20100417140701.15855.26978.stgit@warthog.procyon.org.uk>
Adjust the comment on get_order() to note that the result of passing a size of
0 results in an undefined value.
Signed-off-by: David Howells <dhowells@redhat.com>
---
include/asm-generic/getorder.h | 23 ++++++++++++++++++++++-
1 files changed, 22 insertions(+), 1 deletions(-)
diff --git a/include/asm-generic/getorder.h b/include/asm-generic/getorder.h
index 67e7245..76e9687 100644
--- a/include/asm-generic/getorder.h
+++ b/include/asm-generic/getorder.h
@@ -5,7 +5,28 @@
#include <linux/compiler.h>
-/* Pure 2^n version of get_order */
+/**
+ * get_order - Determine the allocation order of a memory size
+ * @size: The size for which to get the order
+ *
+ * Determine the allocation order of a particular sized block of memory. This
+ * is on a logarithmic scale, where:
+ *
+ * 0 -> 2^0 * PAGE_SIZE and below
+ * 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1
+ * 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1
+ * 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1
+ * 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1
+ * ...
+ *
+ * The order returned is used to find the smallest allocation granule required
+ * to hold an object of the specified size.
+ *
+ * The result is undefined if the size is 0.
+ *
+ * This function may be used to initialise variables with compile time
+ * evaluations of constants.
+ */
static inline __attribute_const__ int get_order(unsigned long size)
{
int order;
next prev parent reply other threads:[~2010-04-17 14:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-17 14:07 [PATCH 1/3] X86_64: Optimise fls(), ffs() and fls64() [ver #2] David Howells
2010-04-17 14:07 ` David Howells [this message]
2010-04-17 14:07 ` [PATCH 3/3] Optimise get_order() " David Howells
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