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Message-Id: <200812091433.03670.rusty@rustcorp.com.au>
Date: Tue, 9 Dec 2008 14:33:03 +1030
From: Rusty Russell <rusty@...tcorp.com.au>
To: Eric Dumazet <dada1@...mosbay.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PACH] smp: uninline num_online_cpus() & num_possible_cpus()
On Saturday 06 December 2008 04:03:44 Eric Dumazet wrote:
> num_online_cpus() and num_possible_cpus() are not performance
> critical and are quite large.
>
> Unlining them shrinks kernel text size by 7523 bytes on x86,
> if NR_CPUS>32
Hi Eric!
Slight misdiagnosis, I think. One base problem is addressed in fixing
the bitmap operators (see "[PATCH] bitmap: test for constant as well as
small size for inline versions" on lkml Message-Id: <200811160907.07140.rusty@...tcorp.com.au>). This is already in
linux-next, and I've pasted it below.
Worse, you used the obsolete cpumask operators :)
Thanks!
Rusty.
bitmap: test for constant as well as small size for inline versions
bitmap_zero et al have a fastpath for nbits <= BITS_PER_LONG, but this
should really only apply where the nbits is known at compile time.
This only saves about 1200 bytes on an allyesconfig kernel, but with
cpumasks going variable that number will increase.
text data bss dec hex filename
35327852 5035607 6782976 47146435 2cf65c3 vmlinux-before
35326640 5035607 6782976 47145223 2cf6107 vmlinux-after
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
---
include/linux/bitmap.h | 35 +++++++++++++++++++----------------
1 file changed, 19 insertions(+), 16 deletions(-)
diff -r b4540ad329c1 include/linux/bitmap.h
--- a/include/linux/bitmap.h Thu Nov 06 13:00:51 2008 +1100
+++ b/include/linux/bitmap.h Thu Nov 06 14:34:07 2008 +1100
@@ -137,9 +137,12 @@ extern void bitmap_copy_le(void *dst, co
(1UL<<((nbits) % BITS_PER_LONG))-1 : ~0UL \
)
+#define small_const_nbits(nbits) \
+ (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG)
+
static inline void bitmap_zero(unsigned long *dst, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
*dst = 0UL;
else {
int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
@@ -150,7 +153,7 @@ static inline void bitmap_fill(unsigned
static inline void bitmap_fill(unsigned long *dst, int nbits)
{
size_t nlongs = BITS_TO_LONGS(nbits);
- if (nlongs > 1) {
+ if (!small_const_nbits(nbits)) {
int len = (nlongs - 1) * sizeof(unsigned long);
memset(dst, 0xff, len);
}
@@ -160,7 +163,7 @@ static inline void bitmap_copy(unsigned
static inline void bitmap_copy(unsigned long *dst, const unsigned long *src,
int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
*dst = *src;
else {
int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
@@ -171,7 +174,7 @@ static inline void bitmap_and(unsigned l
static inline void bitmap_and(unsigned long *dst, const unsigned long *src1,
const unsigned long *src2, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
*dst = *src1 & *src2;
else
__bitmap_and(dst, src1, src2, nbits);
@@ -180,7 +183,7 @@ static inline void bitmap_or(unsigned lo
static inline void bitmap_or(unsigned long *dst, const unsigned long *src1,
const unsigned long *src2, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
*dst = *src1 | *src2;
else
__bitmap_or(dst, src1, src2, nbits);
@@ -189,7 +192,7 @@ static inline void bitmap_xor(unsigned l
static inline void bitmap_xor(unsigned long *dst, const unsigned long *src1,
const unsigned long *src2, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
*dst = *src1 ^ *src2;
else
__bitmap_xor(dst, src1, src2, nbits);
@@ -198,7 +201,7 @@ static inline void bitmap_andnot(unsigne
static inline void bitmap_andnot(unsigned long *dst, const unsigned long *src1,
const unsigned long *src2, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
*dst = *src1 & ~(*src2);
else
__bitmap_andnot(dst, src1, src2, nbits);
@@ -207,7 +210,7 @@ static inline void bitmap_complement(uns
static inline void bitmap_complement(unsigned long *dst, const unsigned long *src,
int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
*dst = ~(*src) & BITMAP_LAST_WORD_MASK(nbits);
else
__bitmap_complement(dst, src, nbits);
@@ -216,7 +219,7 @@ static inline int bitmap_equal(const uns
static inline int bitmap_equal(const unsigned long *src1,
const unsigned long *src2, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
return ! ((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits));
else
return __bitmap_equal(src1, src2, nbits);
@@ -225,7 +228,7 @@ static inline int bitmap_intersects(cons
static inline int bitmap_intersects(const unsigned long *src1,
const unsigned long *src2, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
return ((*src1 & *src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0;
else
return __bitmap_intersects(src1, src2, nbits);
@@ -234,7 +237,7 @@ static inline int bitmap_subset(const un
static inline int bitmap_subset(const unsigned long *src1,
const unsigned long *src2, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
return ! ((*src1 & ~(*src2)) & BITMAP_LAST_WORD_MASK(nbits));
else
return __bitmap_subset(src1, src2, nbits);
@@ -242,7 +245,7 @@ static inline int bitmap_subset(const un
static inline int bitmap_empty(const unsigned long *src, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
return ! (*src & BITMAP_LAST_WORD_MASK(nbits));
else
return __bitmap_empty(src, nbits);
@@ -250,7 +253,7 @@ static inline int bitmap_empty(const uns
static inline int bitmap_full(const unsigned long *src, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
return ! (~(*src) & BITMAP_LAST_WORD_MASK(nbits));
else
return __bitmap_full(src, nbits);
@@ -258,7 +261,7 @@ static inline int bitmap_full(const unsi
static inline int bitmap_weight(const unsigned long *src, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
return hweight_long(*src & BITMAP_LAST_WORD_MASK(nbits));
return __bitmap_weight(src, nbits);
}
@@ -266,7 +269,7 @@ static inline void bitmap_shift_right(un
static inline void bitmap_shift_right(unsigned long *dst,
const unsigned long *src, int n, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
*dst = *src >> n;
else
__bitmap_shift_right(dst, src, n, nbits);
@@ -275,7 +278,7 @@ static inline void bitmap_shift_left(uns
static inline void bitmap_shift_left(unsigned long *dst,
const unsigned long *src, int n, int nbits)
{
- if (nbits <= BITS_PER_LONG)
+ if (small_const_nbits(nbits))
*dst = (*src << n) & BITMAP_LAST_WORD_MASK(nbits);
else
__bitmap_shift_left(dst, src, n, nbits);
--
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