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Groups > linux.kernel > #1487921 > unrolled thread
| Started by | Nicholas Piggin <npiggin@gmail.com> |
|---|---|
| First post | 2016-09-21 11:00 +0200 |
| Last post | 2016-09-23 09:40 +0200 |
| Articles | 10 — 4 participants |
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[PATCH] percpu: improve generic percpu modify-return implementation Nicholas Piggin <npiggin@gmail.com> - 2016-09-21 11:00 +0200
Re: [PATCH] percpu: improve generic percpu modify-return implementation kbuild test robot <lkp@intel.com> - 2016-09-21 12:30 +0200
Re: [PATCH] percpu: improve generic percpu modify-return implementation kbuild test robot <lkp@intel.com> - 2016-09-21 12:40 +0200
Re: [PATCH] percpu: improve generic percpu modify-return implementation Nicholas Piggin <npiggin@gmail.com> - 2016-09-21 13:00 +0200
Re: [PATCH] percpu: improve generic percpu modify-return implementation Tejun Heo <tj@kernel.org> - 2016-09-21 16:30 +0200
Re: [PATCH] percpu: improve generic percpu modify-return implementation Christoph Lameter <cl@linux.com> - 2016-09-21 22:20 +0200
Re: [PATCH] percpu: improve generic percpu modify-return implementation Nicholas Piggin <npiggin@gmail.com> - 2016-09-22 06:50 +0200
Re: [PATCH] percpu: improve generic percpu modify-return implementation Nicholas Piggin <npiggin@gmail.com> - 2016-09-22 07:00 +0200
Re: [PATCH] percpu: improve generic percpu modify-return implementation Tejun Heo <tj@kernel.org> - 2016-09-22 18:10 +0200
Re: [PATCH] percpu: improve generic percpu modify-return implementation Nicholas Piggin <npiggin@gmail.com> - 2016-09-23 09:40 +0200
| From | Nicholas Piggin <npiggin@gmail.com> |
|---|---|
| Date | 2016-09-21 11:00 +0200 |
| Subject | [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <sjLxM-6M9-23@gated-at.bofh.it> |
Some architectures require an additional load to find the address of
percpu pointers. In some implemenatations, the C aliasing rules do not
allow the result of that load to be kept over the store that modifies
the percpu variable, which causes additional loads.
Work around this by finding the pointer first, then operating on that.
It's also possible to mark things as restrict and those kind of games,
but that can require larger and arch specific changes.
On powerpc, __this_cpu_inc_return compiles to:
ld 10,48(13)
ldx 9,3,10
addi 9,9,1
stdx 9,3,10
ld 9,48(13)
ldx 3,9,3
With this patch it saves 2 loads:
ld 10,48(13)
ldx 9,3,10
addi 9,9,1
stdx 9,3,10
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
include/asm-generic/percpu.h | 54 +++++++++++++++++++++++++-------------------
1 file changed, 31 insertions(+), 23 deletions(-)
diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index 4d9f233..3fe18fe 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -65,6 +65,11 @@ extern void setup_per_cpu_areas(void);
#define PER_CPU_DEF_ATTRIBUTES
#endif
+#define raw_cpu_generic_read(pcp) \
+({ \
+ *raw_cpu_ptr(&(pcp)); \
+})
+
#define raw_cpu_generic_to_op(pcp, val, op) \
do { \
*raw_cpu_ptr(&(pcp)) op val; \
@@ -72,34 +77,39 @@ do { \
#define raw_cpu_generic_add_return(pcp, val) \
({ \
- raw_cpu_add(pcp, val); \
- raw_cpu_read(pcp); \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
+ \
+ *__p += val; \
+ *__p; \
})
#define raw_cpu_generic_xchg(pcp, nval) \
({ \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
- __ret = raw_cpu_read(pcp); \
- raw_cpu_write(pcp, nval); \
+ __ret = *__p; \
+ *__p = nval; \
__ret; \
})
#define raw_cpu_generic_cmpxchg(pcp, oval, nval) \
({ \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
- __ret = raw_cpu_read(pcp); \
+ __ret = *__p; \
if (__ret == (oval)) \
- raw_cpu_write(pcp, nval); \
+ *__p = nval; \
__ret; \
})
#define raw_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
({ \
+ typeof(&(pcp1)) __p1 = raw_cpu_ptr(&(pcp1)); \
+ typeof(&(pcp2)) __p2 = raw_cpu_ptr(&(pcp2)); \
int __ret = 0; \
- if (raw_cpu_read(pcp1) == (oval1) && \
- raw_cpu_read(pcp2) == (oval2)) { \
- raw_cpu_write(pcp1, nval1); \
- raw_cpu_write(pcp2, nval2); \
+ if (*__p1 == (oval1) && *__p2 == (oval2)) { \
+ *__p1 = nval1; \
+ *__p2 = nval2; \
__ret = 1; \
} \
(__ret); \
@@ -109,7 +119,7 @@ do { \
({ \
typeof(pcp) __ret; \
preempt_disable(); \
- __ret = *this_cpu_ptr(&(pcp)); \
+ __ret = raw_cpu_generic_read(pcp); \
preempt_enable(); \
__ret; \
})
@@ -118,17 +128,18 @@ do { \
do { \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- *raw_cpu_ptr(&(pcp)) op val; \
+ raw_cpu_generic_to_op(pcp, val, op); \
raw_local_irq_restore(__flags); \
} while (0)
+
#define this_cpu_generic_add_return(pcp, val) \
({ \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- raw_cpu_add(pcp, val); \
- __ret = raw_cpu_read(pcp); \
+ __ret = raw_cpu_generic_add_return(pcp, val); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -138,8 +149,7 @@ do { \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- __ret = raw_cpu_read(pcp); \
- raw_cpu_write(pcp, nval); \
+ __ret = raw_cpu_generic_xchg(pcp); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -149,9 +159,7 @@ do { \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- __ret = raw_cpu_read(pcp); \
- if (__ret == (oval)) \
- raw_cpu_write(pcp, nval); \
+ __ret = raw_cpu_generic_cmpxchg(pcp, oval, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -168,16 +176,16 @@ do { \
})
#ifndef raw_cpu_read_1
-#define raw_cpu_read_1(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_1(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_2
-#define raw_cpu_read_2(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_2(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_4
-#define raw_cpu_read_4(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_4(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_8
-#define raw_cpu_read_8(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_8(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_write_1
--
2.9.3
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| From | kbuild test robot <lkp@intel.com> |
|---|---|
| Date | 2016-09-21 12:30 +0200 |
| Subject | Re: [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <sjMWT-7Q9-59@gated-at.bofh.it> |
| In reply to | #1487921 |
[Multipart message — attachments visible in raw view] — view raw
Hi Nicholas,
[auto build test ERROR on asm-generic/master]
[also build test ERROR on v4.8-rc7 next-20160920]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
[Suggest to use git(>=2.9.0) format-patch --base=<commit> (or --base=auto for convenience) to record what (public, well-known) commit your patch series was built on]
[Check https://git-scm.com/docs/git-format-patch for more information]
url: https://github.com/0day-ci/linux/commits/Nicholas-Piggin/percpu-improve-generic-percpu-modify-return-implementation/20160921-170016
base: https://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git master
config: blackfin-BF561-EZKIT-SMP_defconfig (attached as .config)
compiler: bfin-uclinux-gcc (GCC) 6.2.0
reproduce:
wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=blackfin
All error/warnings (new ones prefixed by >>):
mm/vmstat.c: In function 'refresh_cpu_vm_stats':
>> mm/vmstat.c:476:1: error: macro "raw_cpu_generic_xchg" requires 2 arguments, but only 1 given
v = this_cpu_xchg(p->vm_stat_diff[i], 0);
^ ~~~~~~~~~~~~
In file included from arch/blackfin/include/generated/asm/percpu.h:1:0,
from include/linux/percpu.h:12,
from include/linux/percpu-rwsem.h:6,
from include/linux/fs.h:30,
from mm/vmstat.c:12:
>> include/asm-generic/percpu.h:152:10: error: 'raw_cpu_generic_xchg' undeclared (first use in this function)
__ret = raw_cpu_generic_xchg(pcp); \
^
>> include/asm-generic/percpu.h:382:36: note: in expansion of macro 'this_cpu_generic_xchg'
#define this_cpu_xchg_1(pcp, nval) this_cpu_generic_xchg(pcp, nval)
^~~~~~~~~~~~~~~~~~~~~
>> include/linux/percpu-defs.h:323:24: note: in expansion of macro 'this_cpu_xchg_1'
case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \
^~~~
>> include/linux/percpu-defs.h:500:34: note: in expansion of macro '__pcpu_size_call_return2'
#define this_cpu_xchg(pcp, nval) __pcpu_size_call_return2(this_cpu_xchg_, pcp, nval)
^~~~~~~~~~~~~~~~~~~~~~~~
>> mm/vmstat.c:476:8: note: in expansion of macro 'this_cpu_xchg'
v = this_cpu_xchg(p->vm_stat_diff[i], 0);
^~~~~~~~~~~~~
include/asm-generic/percpu.h:152:10: note: each undeclared identifier is reported only once for each function it appears in
__ret = raw_cpu_generic_xchg(pcp); \
^
>> include/asm-generic/percpu.h:382:36: note: in expansion of macro 'this_cpu_generic_xchg'
#define this_cpu_xchg_1(pcp, nval) this_cpu_generic_xchg(pcp, nval)
^~~~~~~~~~~~~~~~~~~~~
>> include/linux/percpu-defs.h:323:24: note: in expansion of macro 'this_cpu_xchg_1'
case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \
^~~~
>> include/linux/percpu-defs.h:500:34: note: in expansion of macro '__pcpu_size_call_return2'
#define this_cpu_xchg(pcp, nval) __pcpu_size_call_return2(this_cpu_xchg_, pcp, nval)
^~~~~~~~~~~~~~~~~~~~~~~~
>> mm/vmstat.c:476:8: note: in expansion of macro 'this_cpu_xchg'
v = this_cpu_xchg(p->vm_stat_diff[i], 0);
^~~~~~~~~~~~~
>> mm/vmstat.c:476:1: error: macro "raw_cpu_generic_xchg" requires 2 arguments, but only 1 given
v = this_cpu_xchg(p->vm_stat_diff[i], 0);
^ ~~~~~~~~~~~~
>> mm/vmstat.c:476:1: error: macro "raw_cpu_generic_xchg" requires 2 arguments, but only 1 given
>> mm/vmstat.c:476:1: error: macro "raw_cpu_generic_xchg" requires 2 arguments, but only 1 given
vim +/raw_cpu_generic_xchg +476 mm/vmstat.c
ee99c71c KOSAKI Motohiro 2009-03-31 470 for_each_populated_zone(zone) {
fbc2edb0 Christoph Lameter 2013-09-11 471 struct per_cpu_pageset __percpu *p = zone->pageset;
2244b95a Christoph Lameter 2006-06-30 472
fbc2edb0 Christoph Lameter 2013-09-11 473 for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
a7f75e25 Christoph Lameter 2008-02-04 474 int v;
a7f75e25 Christoph Lameter 2008-02-04 475
fbc2edb0 Christoph Lameter 2013-09-11 @476 v = this_cpu_xchg(p->vm_stat_diff[i], 0);
fbc2edb0 Christoph Lameter 2013-09-11 477 if (v) {
fbc2edb0 Christoph Lameter 2013-09-11 478
a7f75e25 Christoph Lameter 2008-02-04 479 atomic_long_add(v, &zone->vm_stat[i]);
:::::: The code at line 476 was first introduced by commit
:::::: fbc2edb05354480a88aa39db8a6acb5782fa1a1b vmstat: use this_cpu() to avoid irqon/off sequence in refresh_cpu_vm_stats
:::::: TO: Christoph Lameter <cl@linux.com>
:::::: CC: Linus Torvalds <torvalds@linux-foundation.org>
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[toc] | [prev] | [next] | [standalone]
| From | kbuild test robot <lkp@intel.com> |
|---|---|
| Date | 2016-09-21 12:40 +0200 |
| Subject | Re: [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <sjN6y-7Tm-39@gated-at.bofh.it> |
| In reply to | #1487921 |
[Multipart message — attachments visible in raw view] — view raw
Hi Nicholas,
[auto build test ERROR on asm-generic/master]
[also build test ERROR on v4.8-rc7 next-20160920]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
[Suggest to use git(>=2.9.0) format-patch --base=<commit> (or --base=auto for convenience) to record what (public, well-known) commit your patch series was built on]
[Check https://git-scm.com/docs/git-format-patch for more information]
url: https://github.com/0day-ci/linux/commits/Nicholas-Piggin/percpu-improve-generic-percpu-modify-return-implementation/20160921-170016
base: https://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git master
config: tile-tilegx_defconfig (attached as .config)
compiler: tilegx-linux-gcc (GCC) 4.6.2
reproduce:
wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=tile
All errors (new ones prefixed by >>):
mm/vmstat.c: In function 'refresh_cpu_vm_stats':
mm/vmstat.c:476:1: error: macro "raw_cpu_generic_xchg" requires 2 arguments, but only 1 given
>> mm/vmstat.c:476:1: error: 'raw_cpu_generic_xchg' undeclared (first use in this function)
mm/vmstat.c:476:1: note: each undeclared identifier is reported only once for each function it appears in
mm/vmstat.c:476:1: error: macro "raw_cpu_generic_xchg" requires 2 arguments, but only 1 given
mm/vmstat.c:476:1: error: macro "raw_cpu_generic_xchg" requires 2 arguments, but only 1 given
mm/vmstat.c:476:1: error: macro "raw_cpu_generic_xchg" requires 2 arguments, but only 1 given
vim +/raw_cpu_generic_xchg +476 mm/vmstat.c
ee99c71c KOSAKI Motohiro 2009-03-31 470 for_each_populated_zone(zone) {
fbc2edb0 Christoph Lameter 2013-09-11 471 struct per_cpu_pageset __percpu *p = zone->pageset;
2244b95a Christoph Lameter 2006-06-30 472
fbc2edb0 Christoph Lameter 2013-09-11 473 for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
a7f75e25 Christoph Lameter 2008-02-04 474 int v;
a7f75e25 Christoph Lameter 2008-02-04 475
fbc2edb0 Christoph Lameter 2013-09-11 @476 v = this_cpu_xchg(p->vm_stat_diff[i], 0);
fbc2edb0 Christoph Lameter 2013-09-11 477 if (v) {
fbc2edb0 Christoph Lameter 2013-09-11 478
a7f75e25 Christoph Lameter 2008-02-04 479 atomic_long_add(v, &zone->vm_stat[i]);
:::::: The code at line 476 was first introduced by commit
:::::: fbc2edb05354480a88aa39db8a6acb5782fa1a1b vmstat: use this_cpu() to avoid irqon/off sequence in refresh_cpu_vm_stats
:::::: TO: Christoph Lameter <cl@linux.com>
:::::: CC: Linus Torvalds <torvalds@linux-foundation.org>
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[toc] | [prev] | [next] | [standalone]
| From | Nicholas Piggin <npiggin@gmail.com> |
|---|---|
| Date | 2016-09-21 13:00 +0200 |
| Subject | Re: [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <sjNpT-7ZV-13@gated-at.bofh.it> |
| In reply to | #1487921 |
On Wed, 21 Sep 2016 18:51:37 +1000
Nicholas Piggin <npiggin@gmail.com> wrote:
> Some architectures require an additional load to find the address of
> percpu pointers. In some implemenatations, the C aliasing rules do not
> allow the result of that load to be kept over the store that modifies
> the percpu variable, which causes additional loads.
Sorry I picked up an old patch here. This one should be better.
From d0cb9052d6f4c31d24f999b7b0cecb34681eee9b Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Wed, 21 Sep 2016 18:23:43 +1000
Subject: [PATCH] percpu: improve generic percpu modify-return implementations
Some architectures require an additional load to find the address of
percpu pointers. In some implemenatations, the C aliasing rules do not
allow the result of that load to be kept over the store that modifies
the percpu variable, which causes additional loads.
Work around this by finding the pointer first, then operating on that.
It's also possible to mark things as restrict and those kind of games,
but that can require larger and arch specific changes.
On powerpc, __this_cpu_inc_return compiles to:
ld 10,48(13)
ldx 9,3,10
addi 9,9,1
stdx 9,3,10
ld 9,48(13)
ldx 3,9,3
With this patch it compiles to:
ld 10,48(13)
ldx 9,3,10
addi 9,9,1
stdx 9,3,10
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
include/asm-generic/percpu.h | 53 +++++++++++++++++++++++++-------------------
1 file changed, 30 insertions(+), 23 deletions(-)
diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index 4d9f233..40e8870 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -65,6 +65,11 @@ extern void setup_per_cpu_areas(void);
#define PER_CPU_DEF_ATTRIBUTES
#endif
+#define raw_cpu_generic_read(pcp) \
+({ \
+ *raw_cpu_ptr(&(pcp)); \
+})
+
#define raw_cpu_generic_to_op(pcp, val, op) \
do { \
*raw_cpu_ptr(&(pcp)) op val; \
@@ -72,34 +77,39 @@ do { \
#define raw_cpu_generic_add_return(pcp, val) \
({ \
- raw_cpu_add(pcp, val); \
- raw_cpu_read(pcp); \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
+ \
+ *__p += val; \
+ *__p; \
})
#define raw_cpu_generic_xchg(pcp, nval) \
({ \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
- __ret = raw_cpu_read(pcp); \
- raw_cpu_write(pcp, nval); \
+ __ret = *__p; \
+ *__p = nval; \
__ret; \
})
#define raw_cpu_generic_cmpxchg(pcp, oval, nval) \
({ \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
- __ret = raw_cpu_read(pcp); \
+ __ret = *__p; \
if (__ret == (oval)) \
- raw_cpu_write(pcp, nval); \
+ *__p = nval; \
__ret; \
})
#define raw_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
({ \
+ typeof(&(pcp1)) __p1 = raw_cpu_ptr(&(pcp1)); \
+ typeof(&(pcp2)) __p2 = raw_cpu_ptr(&(pcp2)); \
int __ret = 0; \
- if (raw_cpu_read(pcp1) == (oval1) && \
- raw_cpu_read(pcp2) == (oval2)) { \
- raw_cpu_write(pcp1, nval1); \
- raw_cpu_write(pcp2, nval2); \
+ if (*__p1 == (oval1) && *__p2 == (oval2)) { \
+ *__p1 = nval1; \
+ *__p2 = nval2; \
__ret = 1; \
} \
(__ret); \
@@ -109,7 +119,7 @@ do { \
({ \
typeof(pcp) __ret; \
preempt_disable(); \
- __ret = *this_cpu_ptr(&(pcp)); \
+ __ret = raw_cpu_generic_read(pcp); \
preempt_enable(); \
__ret; \
})
@@ -118,17 +128,17 @@ do { \
do { \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- *raw_cpu_ptr(&(pcp)) op val; \
+ raw_cpu_generic_to_op(pcp, val, op); \
raw_local_irq_restore(__flags); \
} while (0)
+
#define this_cpu_generic_add_return(pcp, val) \
({ \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- raw_cpu_add(pcp, val); \
- __ret = raw_cpu_read(pcp); \
+ __ret = raw_cpu_generic_add_return(pcp, val); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -138,8 +148,7 @@ do { \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- __ret = raw_cpu_read(pcp); \
- raw_cpu_write(pcp, nval); \
+ __ret = raw_cpu_generic_xchg(pcp, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -149,9 +158,7 @@ do { \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- __ret = raw_cpu_read(pcp); \
- if (__ret == (oval)) \
- raw_cpu_write(pcp, nval); \
+ __ret = raw_cpu_generic_cmpxchg(pcp, oval, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -168,16 +175,16 @@ do { \
})
#ifndef raw_cpu_read_1
-#define raw_cpu_read_1(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_1(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_2
-#define raw_cpu_read_2(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_2(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_4
-#define raw_cpu_read_4(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_4(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_8
-#define raw_cpu_read_8(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_8(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_write_1
--
2.9.3
[toc] | [prev] | [next] | [standalone]
| From | Tejun Heo <tj@kernel.org> |
|---|---|
| Date | 2016-09-21 16:30 +0200 |
| Subject | Re: [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <sjQH7-1Hi-15@gated-at.bofh.it> |
| In reply to | #1488043 |
Hello, Nick. How have you been? :) On Wed, Sep 21, 2016 at 08:57:11PM +1000, Nicholas Piggin wrote: > On Wed, 21 Sep 2016 18:51:37 +1000 > Nicholas Piggin <npiggin@gmail.com> wrote: > > > Some architectures require an additional load to find the address of > > percpu pointers. In some implemenatations, the C aliasing rules do not > > allow the result of that load to be kept over the store that modifies > > the percpu variable, which causes additional loads. > > Sorry I picked up an old patch here. This one should be better. > > From d0cb9052d6f4c31d24f999b7b0cecb34681eee9b Mon Sep 17 00:00:00 2001 > From: Nicholas Piggin <npiggin@gmail.com> > Date: Wed, 21 Sep 2016 18:23:43 +1000 > Subject: [PATCH] percpu: improve generic percpu modify-return implementations > > Some architectures require an additional load to find the address of > percpu pointers. In some implemenatations, the C aliasing rules do not > allow the result of that load to be kept over the store that modifies > the percpu variable, which causes additional loads. > > Work around this by finding the pointer first, then operating on that. > > It's also possible to mark things as restrict and those kind of games, > but that can require larger and arch specific changes. > > On powerpc, __this_cpu_inc_return compiles to: > > ld 10,48(13) > ldx 9,3,10 > addi 9,9,1 > stdx 9,3,10 > ld 9,48(13) > ldx 3,9,3 > > With this patch it compiles to: > > ld 10,48(13) > ldx 9,3,10 > addi 9,9,1 > stdx 9,3,10 > > Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Patch looks good to me but seems QP encoded. Can you please resend? Thanks and it's great to see you again! -- tejun
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| From | Christoph Lameter <cl@linux.com> |
|---|---|
| Date | 2016-09-21 22:20 +0200 |
| Subject | Re: [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <sjW9P-598-31@gated-at.bofh.it> |
| In reply to | #1488157 |
On Wed, 21 Sep 2016, Tejun Heo wrote: > Hello, Nick. > > How have you been? :) > He is baack. Are we getting SL!B? ;-)
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| From | Nicholas Piggin <npiggin@gmail.com> |
|---|---|
| Date | 2016-09-22 06:50 +0200 |
| Subject | Re: [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <sk47n-1KL-15@gated-at.bofh.it> |
| In reply to | #1488376 |
On Wed, 21 Sep 2016 15:16:25 -0500 (CDT) Christoph Lameter <cl@linux.com> wrote: > On Wed, 21 Sep 2016, Tejun Heo wrote: > > > Hello, Nick. > > > > How have you been? :) > > > > He is baack. Are we getting SL!B? ;-) > Hey Christoph. Sure, why not.
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| From | Nicholas Piggin <npiggin@gmail.com> |
|---|---|
| Date | 2016-09-22 07:00 +0200 |
| Subject | Re: [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <sk4h3-1NV-5@gated-at.bofh.it> |
| In reply to | #1488157 |
On Wed, 21 Sep 2016 10:23:43 -0400
Tejun Heo <tj@kernel.org> wrote:
> Hello, Nick.
>
> How have you been? :)
Hey Tejun,
Well thank you, how about you?
> On Wed, Sep 21, 2016 at 08:57:11PM +1000, Nicholas Piggin wrote:
> > On Wed, 21 Sep 2016 18:51:37 +1000
> > Nicholas Piggin <npiggin@gmail.com> wrote:
> >
> > > Some architectures require an additional load to find the address of
> > > percpu pointers. In some implemenatations, the C aliasing rules do not
> > > allow the result of that load to be kept over the store that modifies
> > > the percpu variable, which causes additional loads.
> >
> > Sorry I picked up an old patch here. This one should be better.
> >
> > From d0cb9052d6f4c31d24f999b7b0cecb34681eee9b Mon Sep 17 00:00:00 2001
> > From: Nicholas Piggin <npiggin@gmail.com>
> > Date: Wed, 21 Sep 2016 18:23:43 +1000
> > Subject: [PATCH] percpu: improve generic percpu modify-return implementations
> >
> > Some architectures require an additional load to find the address of
> > percpu pointers. In some implemenatations, the C aliasing rules do not
> > allow the result of that load to be kept over the store that modifies
> > the percpu variable, which causes additional loads.
> >
> > Work around this by finding the pointer first, then operating on that.
> >
> > It's also possible to mark things as restrict and those kind of games,
> > but that can require larger and arch specific changes.
> >
> > On powerpc, __this_cpu_inc_return compiles to:
> >
> > ld 10,48(13)
> > ldx 9,3,10
> > addi 9,9,1
> > stdx 9,3,10
> > ld 9,48(13)
> > ldx 3,9,3
> >
> > With this patch it compiles to:
> >
> > ld 10,48(13)
> > ldx 9,3,10
> > addi 9,9,1
> > stdx 9,3,10
> >
> > Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
>
> Patch looks good to me but seems QP encoded. Can you please resend?
>
> Thanks and it's great to see you again!
>
Trying a new mail client, sorry. It *seems* to be working now, how's
this?
From d0cb9052d6f4c31d24f999b7b0cecb34681eee9b Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Wed, 21 Sep 2016 18:23:43 +1000
Subject: [PATCH] percpu: improve generic percpu modify-return implementations
Some architectures require an additional load to find the address of
percpu pointers. In some implemenatations, the C aliasing rules do not
allow the result of that load to be kept over the store that modifies
the percpu variable, which causes additional loads.
Work around this by finding the pointer first, then operating on that.
It's also possible to mark things as restrict and those kind of games,
but that can require larger and arch specific changes.
On powerpc, __this_cpu_inc_return compiles to:
ld 10,48(13)
ldx 9,3,10
addi 9,9,1
stdx 9,3,10
ld 9,48(13)
ldx 3,9,3
With this patch it compiles to:
ld 10,48(13)
ldx 9,3,10
addi 9,9,1
stdx 9,3,10
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
To: Tejun Heo <tj@kernel.org>
To: Christoph Lameter <cl@linux.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-arch@vger.kernel.org
---
include/asm-generic/percpu.h | 53 +++++++++++++++++++++++++-------------------
1 file changed, 30 insertions(+), 23 deletions(-)
diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index 4d9f233..40e8870 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -65,6 +65,11 @@ extern void setup_per_cpu_areas(void);
#define PER_CPU_DEF_ATTRIBUTES
#endif
+#define raw_cpu_generic_read(pcp) \
+({ \
+ *raw_cpu_ptr(&(pcp)); \
+})
+
#define raw_cpu_generic_to_op(pcp, val, op) \
do { \
*raw_cpu_ptr(&(pcp)) op val; \
@@ -72,34 +77,39 @@ do { \
#define raw_cpu_generic_add_return(pcp, val) \
({ \
- raw_cpu_add(pcp, val); \
- raw_cpu_read(pcp); \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
+ \
+ *__p += val; \
+ *__p; \
})
#define raw_cpu_generic_xchg(pcp, nval) \
({ \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
- __ret = raw_cpu_read(pcp); \
- raw_cpu_write(pcp, nval); \
+ __ret = *__p; \
+ *__p = nval; \
__ret; \
})
#define raw_cpu_generic_cmpxchg(pcp, oval, nval) \
({ \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
- __ret = raw_cpu_read(pcp); \
+ __ret = *__p; \
if (__ret == (oval)) \
- raw_cpu_write(pcp, nval); \
+ *__p = nval; \
__ret; \
})
#define raw_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
({ \
+ typeof(&(pcp1)) __p1 = raw_cpu_ptr(&(pcp1)); \
+ typeof(&(pcp2)) __p2 = raw_cpu_ptr(&(pcp2)); \
int __ret = 0; \
- if (raw_cpu_read(pcp1) == (oval1) && \
- raw_cpu_read(pcp2) == (oval2)) { \
- raw_cpu_write(pcp1, nval1); \
- raw_cpu_write(pcp2, nval2); \
+ if (*__p1 == (oval1) && *__p2 == (oval2)) { \
+ *__p1 = nval1; \
+ *__p2 = nval2; \
__ret = 1; \
} \
(__ret); \
@@ -109,7 +119,7 @@ do { \
({ \
typeof(pcp) __ret; \
preempt_disable(); \
- __ret = *this_cpu_ptr(&(pcp)); \
+ __ret = raw_cpu_generic_read(pcp); \
preempt_enable(); \
__ret; \
})
@@ -118,17 +128,17 @@ do { \
do { \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- *raw_cpu_ptr(&(pcp)) op val; \
+ raw_cpu_generic_to_op(pcp, val, op); \
raw_local_irq_restore(__flags); \
} while (0)
+
#define this_cpu_generic_add_return(pcp, val) \
({ \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- raw_cpu_add(pcp, val); \
- __ret = raw_cpu_read(pcp); \
+ __ret = raw_cpu_generic_add_return(pcp, val); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -138,8 +148,7 @@ do { \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- __ret = raw_cpu_read(pcp); \
- raw_cpu_write(pcp, nval); \
+ __ret = raw_cpu_generic_xchg(pcp, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -149,9 +158,7 @@ do { \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- __ret = raw_cpu_read(pcp); \
- if (__ret == (oval)) \
- raw_cpu_write(pcp, nval); \
+ __ret = raw_cpu_generic_cmpxchg(pcp, oval, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -168,16 +175,16 @@ do { \
})
#ifndef raw_cpu_read_1
-#define raw_cpu_read_1(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_1(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_2
-#define raw_cpu_read_2(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_2(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_4
-#define raw_cpu_read_4(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_4(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_8
-#define raw_cpu_read_8(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_8(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_write_1
--
2.9.3
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| From | Tejun Heo <tj@kernel.org> |
|---|---|
| Date | 2016-09-22 18:10 +0200 |
| Subject | Re: [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <skeJs-7S-27@gated-at.bofh.it> |
| In reply to | #1488533 |
Hello, On Thu, Sep 22, 2016 at 02:35:00PM +1000, Nicholas Piggin wrote: > Well thank you, how about you? Heh, can't complain. Hope to see you around sometime. It's been forever. > Trying a new mail client, sorry. It *seems* to be working now, how's > this? Hmm... Still encoded. > From d0cb9052d6f4c31d24f999b7b0cecb34681eee9b Mon Sep 17 00:00:00 2001 > From: Nicholas Piggin <npiggin@gmail.com> > Date: Wed, 21 Sep 2016 18:23:43 +1000 > Subject: [PATCH] percpu: improve generic percpu modify-return implementations > > Some architectures require an additional load to find the address of > percpu pointers. In some implemenatations, the C aliasing rules do not > allow the result of that load to be kept over the store that modifies > the percpu variable, which causes additional loads. > > Work around this by finding the pointer first, then operating on that. > > It's also possible to mark things as restrict and those kind of games, > but that can require larger and arch specific changes. QP-decoded and applied to percpu/for-4.9. Thanks. -- tejun
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| From | Nicholas Piggin <npiggin@gmail.com> |
|---|---|
| Date | 2016-09-23 09:40 +0200 |
| Subject | Re: [PATCH] percpu: improve generic percpu modify-return implementation |
| Message-ID | <sktfs-JS-35@gated-at.bofh.it> |
| In reply to | #1489070 |
On Thu, 22 Sep 2016 12:07:49 -0400 Tejun Heo <tj@kernel.org> wrote: > Hello, > > On Thu, Sep 22, 2016 at 02:35:00PM +1000, Nicholas Piggin wrote: > > Well thank you, how about you? > > Heh, can't complain. Hope to see you around sometime. It's been > forever. Yeah, it has been. Hopefully I'll see you around. > > Trying a new mail client, sorry. It *seems* to be working now, how's > > this? > > Hmm... Still encoded. It looks to be a helpful surprise feature of claws. Any line starting with the word "From" make it go q-p due to some mail servers treating that differently. Sigh. > > > From d0cb9052d6f4c31d24f999b7b0cecb34681eee9b Mon Sep 17 00:00:00 2001 > > From: Nicholas Piggin <npiggin@gmail.com> > > Date: Wed, 21 Sep 2016 18:23:43 +1000 > > Subject: [PATCH] percpu: improve generic percpu modify-return implementations > > > > Some architectures require an additional load to find the address of > > percpu pointers. In some implemenatations, the C aliasing rules do not > > allow the result of that load to be kept over the store that modifies > > the percpu variable, which causes additional loads. > > > > Work around this by finding the pointer first, then operating on that. > > > > It's also possible to mark things as restrict and those kind of games, > > but that can require larger and arch specific changes. > > QP-decoded and applied to percpu/for-4.9. > > Thanks. > Thanks!
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