Thread: faster version of AllocSetFreeIndex for x86 architecture
Hi,
I made a faster version of AllocSetFreeIndex for x86 architecture.
Attached files are benchmark programs and patch file.
alloc_test.pl: benchmark script
alloc_test.c: benchmark program
aset_free_index.patch: patch for util/mmgr/aset.c
This benchmark compares the original function with a faster version.
To try the benchmark, only execute alloc_test.pl. This script compiles
alloc_test.c and execute the benchmark.
Results of benchmark script:
Xeon(Core architecture), RedHat EL4, gcc 3.4.6
bytes : 4 8 16 32 64 128 256 512 1024 mix
original: 0.780 0.780 0.820 0.870 0.930 0.970 1.030 1.080 1.130 0.950
patched : 0.380 0.170 0.170 0.170 0.170 0.180 0.170 0.180 0.180 0.280
Core2, Windows XP, gcc 3.4.4 (cygwin)
bytes : 4 8 16 32 64 128 256 512 1024 mix
original: 0.249 0.249 0.515 0.452 0.577 0.671 0.796 0.890 0.999 1.577
patched : 0.358 0.218 0.202 0.218 0.218 0.218 0.202 0.218 0.218 0.218
Xeon(Pentium4 architecture), RedHal EL4, gcc 3.4.6
bytes : 4 8 16 32 64 128 256 512 1024 mix
original: 0.510 0.520 0.620 0.860 0.970 1.260 1.150 1.220 1.290 0.860
patched : 0.620 0.530 0.530 0.540 0.540 0.530 0.540 0.530 0.530 0.490
The effect of the patch that I measured by oprofile is:
- test program: pgbench -c 1 -t 50000 (fsync=off)
original:
CPU: P4 / Xeon with 2 hyper-threads, speed 2793.55 MHz (estimated)
Counted GLOBAL_POWER_EVENTS events
with a unit mask of 0x01 (mandatory) count 100000
samples % symbol name
66854 6.6725 AllocSetAlloc
47679 4.7587 base_yyparse
29058 2.9002 hash_search_with_hash_value
22053 2.2011 SearchCatCache
19264 1.9227 MemoryContextAllocZeroAligned
16223 1.6192 base_yylex
13819 1.3792 ScanKeywordLookup
13305 1.3279 expression_tree_walker
12144 1.2121 LWLockAcquire
11850 1.1827 XLogInsert
11817 1.1794 AllocSetFree
patched:
CPU: P4 / Xeon with 2 hyper-threads, speed 2793.55 MHz (estimated)
Counted GLOBAL_POWER_EVENTS events
with a unit mask of 0x01 (mandatory) count 100000
samples % symbol name
47610 4.9333 AllocSetAlloc
47441 4.9158 base_yyparse
28243 2.9265 hash_search_with_hash_value
22197 2.3000 SearchCatCache
18984 1.9671 MemoryContextAllocZeroAligned
15747 1.6317 base_yylex
13368 1.3852 ScanKeywordLookup
12889 1.3356 expression_tree_walker
12092 1.2530 LWLockAcquire
12078 1.2515 XLogInsert
(skip)
6248 0.6474 AllocSetFree
I think this patch improves AllocSetAlloc/AllocSetFree performance.
Best regards,
---
Atsushi Ogawa
a_ogawa@hi-ho.ne.jp
#!/usr/bin/perl
system "gcc -O2 -o alloc_test alloc_test.c";
my @test_bytes = (4,8,16,32,64,128,256,512,1024,
'8 16 28 36 12 4 8 64 1024 8 24 12 8 64 16');
my $cnt = 10000000;
my @old_result;
my @new_result;
my $t0, $t1, $e;
foreach $e (@test_bytes) {
$t0 = (times)[2];
system "./alloc_test old $cnt $e";
push @old_result, (times)[2] - $t0;
$t0 = (times)[2];
system "./alloc_test new $cnt $e";
push @new_result, (times)[2] - $t0;
}
print " bytes : ";
foreach $e (@test_bytes) {
$e = 'mix' if($e =~ /\d+ \d+/);
printf("%5s ", $e);
}
print "\n";
print " original: ";
foreach $e (@old_result) { printf("%.3f ", $e); }
print "\n";
print " patched : ";
foreach $e (@new_result) { printf("%.3f ", $e); }
print "\n";
#include <stdio.h>
#define Assert(condition)
#define ALLOC_MINBITS 3
#define ALLOCSET_NUM_FREELISTS 11
typedef size_t Size;
/*
* faster version of AllocSetFreeIndex for x86 architecure.
* this function runs in O(1).
*/
static inline int
AllocSetFreeIndex_new(Size size)
{
int idx;
if (__builtin_expect(size < (1 << ALLOC_MINBITS), 0))
size = (1 << ALLOC_MINBITS);
/* bsr(Bit Scan Reverse): Search the most significant set bit */
__asm__ ("bsr %1, %0" :"=r"(idx) :"g"(size - 1));
return idx - (ALLOC_MINBITS - 1);
}
static inline int
AllocSetFreeIndex(Size size)
{
int idx = 0;
if (size > 0)
{
size = (size - 1) >> ALLOC_MINBITS;
while (size != 0)
{
idx++;
size >>= 1;
}
Assert(idx < ALLOCSET_NUM_FREELISTS);
}
return idx;
}
int main(int argc, char *argv[])
{
int loop_cnt;
int size[16];
int i, j;
int result = 0;
if(argc < 4) {
fprintf(stderr, "usage: asettest (new|old) loop_cnt size...\n");
return 1;
}
loop_cnt = atoi(argv[2]);
for(i = 0; i < 16; i++) {
if(argc <= i + 3) {
size[i] = size[0];
} else {
size[i] = atoi(argv[i + 3]);
}
}
if(strcmp(argv[1], "new") == 0) {
for(i = 0; i < loop_cnt; i++) {
for(j = 0; j < 16; j++) {
result += AllocSetFreeIndex_new(size[j]);
}
}
} else if(strcmp(argv[1], "old") == 0) {
for(i = 0; i < loop_cnt; i++) {
for(j = 0; j < 16; j++) {
result += AllocSetFreeIndex(size[j]);
}
}
} else {
fprintf(stderr, "usage: asettest (new|old) size loop_cnt\n");
return 1;
}
fprintf(stderr, "%s, size:%d, loop:%d, checksum:%d\n",
argv[1], size[0], loop_cnt, result);
return 0;
}
*** ./src/backend/utils/mmgr/aset.c.orig 2009-06-01 23:12:10.000000000 +0900
--- ./src/backend/utils/mmgr/aset.c 2009-06-02 08:47:30.000000000 +0900
***************
*** 263,268 ****
--- 263,287 ----
* that size <= ALLOC_CHUNK_LIMIT.
* ----------
*/
+ #if defined(__i386__) && defined(__GNUC__)
+ /*
+ * faster version of AllocSetFreeIndex for x86 architecure.
+ * this function runs in O(1).
+ */
+ static inline int
+ AllocSetFreeIndex(Size size)
+ {
+ int idx;
+
+ if (__builtin_expect(size < (1 << ALLOC_MINBITS), 0))
+ size = (1 << ALLOC_MINBITS);
+
+ /* bsr(Bit Scan Reverse): Search the most significant set bit */
+ __asm__ ("bsr %1, %0" :"=r"(idx) :"g"(size - 1));
+
+ return idx - (ALLOC_MINBITS - 1);
+ }
+ #else
static inline int
AllocSetFreeIndex(Size size)
{
***************
*** 281,286 ****
--- 300,306 ----
return idx;
}
+ #endif /* defined(__i386__) && defined(__GNUC__) */
#ifdef RANDOMIZE_ALLOCATED_MEMORY
Hi,
> I made a faster version of AllocSetFreeIndex for x86 architecture.
Neat, I have a version for PowerPC too.
In order to prevent writing multiple copies of AllocSetFreeIndex, I
propose that we add a fls() function ("find last set"); this can be
defined in an architecture-independent manner (ie, shift mask & test in
a loop), and re-defined for arches that have faster ways of doing the
same (ie, cntlz instruction on powerpc).
We can then change AllocSetFreeIndex to use fls().
Patches coming...
Jeremy
Add a utility header for simple bit operatios - bitops.h.
At present, just contains the fls() (find last set bit) function.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
---src/include/utils/bitops.h | 52 +++++++++++++++++++++++++++++++++++++++++++++1 file changed, 52 insertions(+)
diff --git a/src/include/utils/bitops.h b/src/include/utils/bitops.h
new file mode 100644
index 0000000..de11624
--- /dev/null
+++ b/src/include/utils/bitops.h
@@ -0,0 +1,52 @@
+/*-------------------------------------------------------------------------
+ *
+ * bitops.h
+ * Simple bit operations.
+ *
+ * Portions Copyright (c) 2009, PostgreSQL Global Development Group
+ *
+ * $PostgreSQL$
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef BITOPS_H
+#define BITOPS_H
+
+#if defined(__ppc__) || defined(__powerpc__) || \
+ defined(__ppc64__) || defined (__powerpc64__)
+
+static inline int
+fls(unsigned int x)
+{
+ int lz;
+ asm("cntlz %0,%1" : "=r" (lz) : "r" (x));
+ return 32 - lz;
+}
+
+#else /* !powerpc */
+
+/* Architecture-independent implementations */
+
+/*
+ * fls: find last set bit.
+ *
+ * Returns the 1-based index of the most-significant bit in x. The MSB
+ * is bit number 32, the LSB is bit number 1. If x is zero, returns zero.
+ */
+static inline int
+fls(unsigned int x)
+{
+ int ls = 0;
+
+ while (x != 0)
+ {
+ ls++;
+ x >>= 1;
+ }
+
+ return ls;
+}
+
+#endif
+
+#endif /* BITOPS_H */
Results in a ~2% performance increase by using the powerpc fls()
implementation.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
---src/backend/utils/mmgr/aset.c | 8 ++------1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c
index 0e2d4d5..762cf72 100644
--- a/src/backend/utils/mmgr/aset.c
+++ b/src/backend/utils/mmgr/aset.c
@@ -65,6 +65,7 @@#include "postgres.h"#include "utils/memutils.h"
+#include "utils/bitops.h"/* Define this to detail debug alloc information *//* #define HAVE_ALLOCINFO */
@@ -270,12 +271,7 @@ AllocSetFreeIndex(Size size) if (size > 0) {
- size = (size - 1) >> ALLOC_MINBITS;
- while (size != 0)
- {
- idx++;
- size >>= 1;
- }
+ idx = fls((size - 1) >> ALLOC_MINBITS); Assert(idx < ALLOCSET_NUM_FREELISTS); }
Jeremy Kerr <jk@ozlabs.org> writes:
> Add a utility header for simple bit operatios - bitops.h.
This will fail outright on any non-gcc compiler.
regards, tom lane
Add a utility header for simple bit operatios - bitops.h.
At present, just contains the fls() (find last set bit) function.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
---
v2: only use inline asm with gcc
---src/include/utils/bitops.h | 53 +++++++++++++++++++++++++++++++++++++++++++++1 file changed, 53 insertions(+)
diff --git a/src/include/utils/bitops.h b/src/include/utils/bitops.h
new file mode 100644
index 0000000..4f2bbc9
--- /dev/null
+++ b/src/include/utils/bitops.h
@@ -0,0 +1,53 @@
+/*-------------------------------------------------------------------------
+ *
+ * bitops.h
+ * Simple bit operations.
+ *
+ * Portions Copyright (c) 2009, PostgreSQL Global Development Group
+ *
+ * $PostgreSQL$
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef BITOPS_H
+#define BITOPS_H
+
+#if defined(__GNUC__) && \
+ (defined(__ppc__) || defined(__powerpc__) || \
+ defined(__ppc64__) || defined (__powerpc64__))
+
+static inline int
+fls(unsigned int x)
+{
+ int lz;
+ asm("cntlz %0,%1" : "=r" (lz) : "r" (x));
+ return 32 - lz;
+}
+
+#else /* !(gcc && powerpc) */
+
+/* Architecture-independent implementations */
+
+/*
+ * fls: find last set bit.
+ *
+ * Returns the 1-based index of the most-significant bit in x. The MSB
+ * is bit number 32, the LSB is bit number 1. If x is zero, returns zero.
+ */
+static inline int
+fls(unsigned int x)
+{
+ int ls = 0;
+
+ while (x != 0)
+ {
+ ls++;
+ x >>= 1;
+ }
+
+ return ls;
+}
+
+#endif
+
+#endif /* BITOPS_H */
* Jeremy Kerr: > +#if defined(__GNUC__) && \ > + (defined(__ppc__) || defined(__powerpc__) || \ > + defined(__ppc64__) || defined (__powerpc64__)) If you require GCC anyway, you can use __builtin_clz instead. (It's been available since GCC 4.1 at least.) -- Florian Weimer <fweimer@bfk.de> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99
Florian, > > +#if defined(__GNUC__) && \ > > + (defined(__ppc__) || defined(__powerpc__) || \ > > + defined(__ppc64__) || defined (__powerpc64__)) > > If you require GCC anyway, you can use __builtin_clz instead. > (It's been available since GCC 4.1 at least.) Because now we have to test the compiler *and* the version as well? But I do agree that using the builtins makes for much better code; I'm looking at a future change that does this. Cheers, Jeremy
* Jeremy Kerr: > Florian, > >> > +#if defined(__GNUC__) && \ >> > + (defined(__ppc__) || defined(__powerpc__) || \ >> > + defined(__ppc64__) || defined (__powerpc64__)) >> >> If you require GCC anyway, you can use __builtin_clz instead. >> (It's been available since GCC 4.1 at least.) > > Because now we have to test the compiler *and* the version as well? This builtin is not architecture-specific, so you'd save the architecture check. -- Florian Weimer <fweimer@bfk.de> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99
Florian Weimer <fweimer@bfk.de> writes:
> * Jeremy Kerr:
>> Because now we have to test the compiler *and* the version as well?
> This builtin is not architecture-specific, so you'd save the
> architecture check.
The appropriate way to handle it would be a configure probe to see if
the function is available, thus avoiding any wired-in knowledge about
compiler or compiler version *or* architecture.
The other thing I didn't like about the patch was the assumption that
it's okay to have a "static inline" function in a header. You can
get away with that in gcc but *not* in other compilers. Look at the
existing coding patterns for, eg, list_head; then go thou and do
likewise. Or, since there's currently no need for the code outside
aset.c, forget about putting it in a header and just plop it into
aset.c.
regards, tom lane
Hi Tom, > The other thing I didn't like about the patch was the assumption that > it's okay to have a "static inline" function in a header. You can > get away with that in gcc but *not* in other compilers. Gee, you user-space guys have it tough! :D Point taken, will rework. > Look at the existing coding patterns for, eg, list_head; then go thou > and do likewise. Or, since there's currently no need for the code > outside aset.c, forget about putting it in a header and just plop it > into aset.c. OK, I'll add a configure check and conditionally use the builtin if it's available. I have some other patches that could be improved by using other builtins, so it would be a good opportunity to figure out a nice pattern for doing this. Cheers, Jeremy
Move the shift-and-test login into a separate fls() function, which
can use __builtin_clz() if it's available.
This requires a new check for __builtin_clz in the configure script.
Results in a ~2% performance increase on PowerPC.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
---configure.in | 13 +++++++++++++src/backend/utils/mmgr/aset.c | 32
++++++++++++++++++++++++++------2files changed, 39 insertions(+), 6 deletions(-)
diff --git a/configure.in b/configure.in
index b8d2685..6a317b0 100644
--- a/configure.in
+++ b/configure.in
@@ -1361,6 +1361,19 @@ case $host_os in AC_FUNC_FSEEKO;;esac
+# GCC builtins
+#
+# We need AC_TRY_LINK here, as the prototype generated by AC_CHECK_FUNC
+# will cause gcc to try to reference a non-builtin symbol.
+
+AC_MSG_CHECKING([for __builtin_clz])
+AC_TRY_LINK([],
+ [__builtin_clz(0);],
+ [AC_DEFINE(HAVE_BUILTIN_CLZ, 1,
+ [Define to 1 if you have __builtin_clz().])
+ AC_MSG_RESULT(yes)],
+ [AC_MSG_RESULT(no)])
+## Pthreads
diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c
index 0e2d4d5..af352b8 100644
--- a/src/backend/utils/mmgr/aset.c
+++ b/src/backend/utils/mmgr/aset.c
@@ -255,6 +255,31 @@ static MemoryContextMethods AllocSetMethods = {#define AllocAllocInfo(_cxt, _chunk)#endif
+/*
+ * fls: find last set bit.
+ *
+ * Returns the 1-based index of the most-significant bit in x. The MSB
+ * is bit number 32, the LSB is bit number 1. If x is zero, the result is
+ * undefined.
+ */
+static inline int
+fls(unsigned int x)
+{
+#ifdef HAVE_BUILTIN_CLZ
+ return 32 - __builtin_clz(x);
+#else
+ int ls = 0;
+
+ while (x != 0)
+ {
+ ls++;
+ x >>= 1;
+ }
+
+ return ls;
+#endif
+}
+/* ---------- * AllocSetFreeIndex - *
@@ -270,12 +295,7 @@ AllocSetFreeIndex(Size size) if (size > 0) {
- size = (size - 1) >> ALLOC_MINBITS;
- while (size != 0)
- {
- idx++;
- size >>= 1;
- }
+ idx = fls((size - 1) >> ALLOC_MINBITS); Assert(idx < ALLOCSET_NUM_FREELISTS); }
> +/*
> + * fls: find last set bit.
> + *
> + * Returns the 1-based index of the most-significant bit in x. The MSB
> + * is bit number 32, the LSB is bit number 1. If x is zero, the result is
> + * undefined.
> + */
> +static inline int
> +fls(unsigned int x)
...
> + idx = fls((size - 1) >> ALLOC_MINBITS);
If size <= 8, fls((size - 1) >> ALLOC_MINBITS) is fls(0).
The result of fls(0) is undefined.
I think we have to never call fls(0) from AllocSetFreeIndex().
My proposal code:
if (size > (1 << ALLOC_MINBITS)) { idx = fls((size - 1) >> ALLOC_MINBITS); Assert(idx <
ALLOCSET_NUM_FREELISTS); }
Best regards,
---
Atsushi Ogawa
On Tue, 2009-06-02 at 23:53 +0900, Atsushi Ogawa wrote: > I made a faster version of AllocSetFreeIndex for x86 architecture. > Results of benchmark script: > Xeon(Core architecture), RedHat EL4, gcc 3.4.6 > bytes : 4 8 16 32 64 128 256 512 1024 mix > original: 0.780 0.780 0.820 0.870 0.930 0.970 1.030 1.080 1.130 0.950 > patched : 0.380 0.170 0.170 0.170 0.170 0.180 0.170 0.180 0.180 0.280 > The effect of the patch that I measured by oprofile is: > - test program: pgbench -c 1 -t 50000 (fsync=off) > > original: > CPU: P4 / Xeon with 2 hyper-threads, speed 2793.55 MHz (estimated) > Counted GLOBAL_POWER_EVENTS events > with a unit mask of 0x01 (mandatory) count 100000 > samples % symbol name > 66854 6.6725 AllocSetAlloc > patched: > CPU: P4 / Xeon with 2 hyper-threads, speed 2793.55 MHz (estimated) > Counted GLOBAL_POWER_EVENTS events > with a unit mask of 0x01 (mandatory) count 100000 > samples % symbol name > 47610 4.9333 AllocSetAlloc > I think this patch improves AllocSetAlloc/AllocSetFree performance. Looks like very good work. Much appreciated. -- Simon Riggs www.2ndQuadrant.comPostgreSQL Training, Services and Support
Hi Atsushi,
> If size <= 8, fls((size - 1) >> ALLOC_MINBITS) is fls(0).
> The result of fls(0) is undefined.
Yep, got caught out by this because my previous fls() supported zero.
> I think we have to never call fls(0) from AllocSetFreeIndex().
> My proposal code:
>
> if (size > (1 << ALLOC_MINBITS))
> {
> idx = fls((size - 1) >> ALLOC_MINBITS);
> Assert(idx < ALLOCSET_NUM_FREELISTS);
> }
Looks good, I'll send an updated patch.
Also, are you still seeing the same improvement with the __builtin_clz
as your inline asm implementation?
Cheers,
Jeremy
Move the shift-and-test login into a separate fls() function, which
can use __builtin_clz() if it's available.
This requires a new check for __builtin_clz in the configure script.
Results in a ~2% performance increase on PowerPC.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
---
v2: prevent fls(0)
---configure.in | 13 +++++++++++++src/backend/utils/mmgr/aset.c | 34
+++++++++++++++++++++++++++-------2files changed, 40 insertions(+), 7 deletions(-)
diff --git a/configure.in b/configure.in
index b8d2685..6a317b0 100644
--- a/configure.in
+++ b/configure.in
@@ -1361,6 +1361,19 @@ case $host_os in AC_FUNC_FSEEKO;;esac
+# GCC builtins
+#
+# We need AC_TRY_LINK here, as the prototype generated by AC_CHECK_FUNC
+# will cause gcc to try to reference a non-builtin symbol.
+
+AC_MSG_CHECKING([for __builtin_clz])
+AC_TRY_LINK([],
+ [__builtin_clz(0);],
+ [AC_DEFINE(HAVE_BUILTIN_CLZ, 1,
+ [Define to 1 if you have __builtin_clz().])
+ AC_MSG_RESULT(yes)],
+ [AC_MSG_RESULT(no)])
+## Pthreads
diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c
index 0e2d4d5..9eb3117 100644
--- a/src/backend/utils/mmgr/aset.c
+++ b/src/backend/utils/mmgr/aset.c
@@ -255,6 +255,31 @@ static MemoryContextMethods AllocSetMethods = {#define AllocAllocInfo(_cxt, _chunk)#endif
+/*
+ * fls: find last set bit.
+ *
+ * Returns the 1-based index of the most-significant bit in x. The MSB
+ * is bit number 32, the LSB is bit number 1. If x is zero, the result is
+ * undefined.
+ */
+static inline int
+fls(unsigned int x)
+{
+#ifdef HAVE_BUILTIN_CLZ
+ return 32 - __builtin_clz(x);
+#else
+ int ls = 0;
+
+ while (x != 0)
+ {
+ ls++;
+ x >>= 1;
+ }
+
+ return ls;
+#endif
+}
+/* ---------- * AllocSetFreeIndex - *
@@ -268,14 +293,9 @@ AllocSetFreeIndex(Size size){ int idx = 0;
- if (size > 0)
+ if (size > (1 << ALLOC_MINBITS)) {
- size = (size - 1) >> ALLOC_MINBITS;
- while (size != 0)
- {
- idx++;
- size >>= 1;
- }
+ idx = fls((size - 1) >> ALLOC_MINBITS); Assert(idx < ALLOCSET_NUM_FREELISTS); }
Hi, > Also, are you still seeing the same improvement with the __builtin_clz > as your inline asm implementation? In my benchmark program, it is a little different performance in fls implementation and inline asm implementation. However, the result of a pgbench is almost the same improvement. Here is the result of my benchmark. Xeon(Core architecture) bytes : 4 8 16 32 64 128 256 512 1024 mix original : 0.780 0.790 0.8200.870 0.930 0.980 1.040 1.080 1.140 0.910 inline asm: 0.320 0.180 0.190 0.180 0.190 0.180 0.190 0.180 0.190 0.170 fls : 0.270 0.260 0.290 0.290 0.290 0.290 0.290 0.300 0.290 0.380 Xeon(P4 architecrure) bytes : 4 8 16 32 64 128 256 512 1024 mix original : 0.520 0.520 0.6700.780 0.950 1.000 1.060 1.190 1.250 0.940 inline asm: 0.610 0.530 0.530 0.520 0.520 0.540 0.540 0.580 0.540 0.600 fls : 0.390 0.370 0.780 0.780 0.780 0.790 0.780 0.780 0.780 0.520 pgbench result (measured by oprofile) CPU: Xeon(P4 architecrure) test program: pgbench -c 1 -t 50000 (fsync=off) original samples % symbol name 66854 6.6725 AllocSetAlloc 11817 1.1794 AllocSetFree inline asm samples % symbol name 47610 4.9333 AllocSetAlloc 6248 0.6474 AllocSetFree fls samples % symbol name 48779 4.9954 AllocSetAlloc 7648 0.7832 AllocSetFree Best regards, --- Atsushi Ogawa
Hi Atsushi, > In my benchmark program, it is a little different performance > in fls implementation and inline asm implementation. > However, the result of a pgbench is almost the same improvement. > > Here is the result of my benchmark. Excellent, thank you for getting this extra set of numbers. Cheers, Jeremy