* [PATCH] kstat_this_cpu in terms of __get_cpu_var and use it
@ 2003-07-04 1:53 Rusty Russell
2003-07-04 2:24 ` Linus Torvalds
0 siblings, 1 reply; 3+ messages in thread
From: Rusty Russell @ 2003-07-04 1:53 UTC (permalink / raw)
To: torvalds; +Cc: linux-kernel, trivial
Linus, please apply.
kstat_this_cpu() is defined in terms of per_cpu instead of __get_cpu_var.
This patch changes that, and uses it where appropriate.
Name: Make kstat_this_cpu in terms of __get_cpu_var and use it
Author: Rusty Russell
Status: Tested on 2.5.74-bk1
D: kstat_this_cpu is defined in terms of per_cpu instead of __get_cpu_var.
D: This patch changes that, and uses it everywhere appropriate.
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .19878-linux-2.5.74-bk1/arch/i386/kernel/irq.c .19878-linux-2.5.74-bk1.updated/arch/i386/kernel/irq.c
--- .19878-linux-2.5.74-bk1/arch/i386/kernel/irq.c 2003-06-15 11:29:47.000000000 +1000
+++ .19878-linux-2.5.74-bk1.updated/arch/i386/kernel/irq.c 2003-07-04 11:40:36.000000000 +1000
@@ -416,7 +416,6 @@ asmlinkage unsigned int do_IRQ(struct pt
* handled by some other CPU. (or is disabled)
*/
int irq = regs.orig_eax & 0xff; /* high bits used in ret_from_ code */
- int cpu = smp_processor_id();
irq_desc_t *desc = irq_desc + irq;
struct irqaction * action;
unsigned int status;
@@ -437,7 +436,7 @@ asmlinkage unsigned int do_IRQ(struct pt
}
}
#endif
- kstat_cpu(cpu).irqs[irq]++;
+ kstat_this_cpu.irqs[irq]++;
spin_lock(&desc->lock);
desc->handler->ack(irq);
/*
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .19878-linux-2.5.74-bk1/include/linux/kernel_stat.h .19878-linux-2.5.74-bk1.updated/include/linux/kernel_stat.h
--- .19878-linux-2.5.74-bk1/include/linux/kernel_stat.h 2003-02-07 19:17:07.000000000 +1100
+++ .19878-linux-2.5.74-bk1.updated/include/linux/kernel_stat.h 2003-07-04 11:39:39.000000000 +1000
@@ -31,7 +31,8 @@ struct kernel_stat {
DECLARE_PER_CPU(struct kernel_stat, kstat);
#define kstat_cpu(cpu) per_cpu(kstat, cpu)
-#define kstat_this_cpu kstat_cpu(smp_processor_id())
+/* Must have preemption disabled for this to be meaningful. */
+#define kstat_this_cpu __get_cpu_var(kstat)
extern unsigned long nr_context_switches(void);
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .19878-linux-2.5.74-bk1/kernel/sched.c .19878-linux-2.5.74-bk1.updated/kernel/sched.c
--- .19878-linux-2.5.74-bk1/kernel/sched.c 2003-07-03 09:44:01.000000000 +1000
+++ .19878-linux-2.5.74-bk1.updated/kernel/sched.c 2003-07-04 11:39:39.000000000 +1000
@@ -1184,19 +1184,19 @@ void scheduler_tick(int user_ticks, int
if (p == rq->idle) {
/* note: this timer irq context must be accounted for as well */
if (irq_count() - HARDIRQ_OFFSET >= SOFTIRQ_OFFSET)
- kstat_cpu(cpu).cpustat.system += sys_ticks;
+ kstat_this_cpu.cpustat.system += sys_ticks;
else if (atomic_read(&rq->nr_iowait) > 0)
- kstat_cpu(cpu).cpustat.iowait += sys_ticks;
+ kstat_this_cpu.cpustat.iowait += sys_ticks;
else
- kstat_cpu(cpu).cpustat.idle += sys_ticks;
+ kstat_this_cpu.cpustat.idle += sys_ticks;
rebalance_tick(rq, 1);
return;
}
if (TASK_NICE(p) > 0)
- kstat_cpu(cpu).cpustat.nice += user_ticks;
+ kstat_this_cpu.cpustat.nice += user_ticks;
else
- kstat_cpu(cpu).cpustat.user += user_ticks;
- kstat_cpu(cpu).cpustat.system += sys_ticks;
+ kstat_this_cpu.cpustat.user += user_ticks;
+ kstat_this_cpu.cpustat.system += sys_ticks;
/* Task might have expired already, but not scheduled off yet */
if (p->array != rq->active) {
--
Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] kstat_this_cpu in terms of __get_cpu_var and use it
2003-07-04 1:53 [PATCH] kstat_this_cpu in terms of __get_cpu_var and use it Rusty Russell
@ 2003-07-04 2:24 ` Linus Torvalds
2003-07-07 5:32 ` Rusty Russell
0 siblings, 1 reply; 3+ messages in thread
From: Linus Torvalds @ 2003-07-04 2:24 UTC (permalink / raw)
To: Rusty Russell; +Cc: Kernel Mailing List, trivial
On Fri, 4 Jul 2003, Rusty Russell wrote:
>
> kstat_this_cpu() is defined in terms of per_cpu instead of __get_cpu_var.
> This patch changes that, and uses it where appropriate.
This makes some things much slower, since we'll re-compute the cpu number
over and over and over again.
This per-cpu'ification has to stop if it just makes code slower.
Linus
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] kstat_this_cpu in terms of __get_cpu_var and use it
2003-07-04 2:24 ` Linus Torvalds
@ 2003-07-07 5:32 ` Rusty Russell
0 siblings, 0 replies; 3+ messages in thread
From: Rusty Russell @ 2003-07-07 5:32 UTC (permalink / raw)
To: Linus Torvalds; +Cc: Kernel Mailing List, trivial
In message <Pine.LNX.4.44.0307031923230.3664-100000@home.osdl.org> you write:
>
> On Fri, 4 Jul 2003, Rusty Russell wrote:
> >
> > kstat_this_cpu() is defined in terms of per_cpu instead of __get_cpu_var.
> > This patch changes that, and uses it where appropriate.
>
> This makes some things much slower, since we'll re-compute the cpu number
> over and over and over again.
Not quite, even on i386.
I did actually test the gcc 3.3 x86 output on other examples: it's
quite happy to optimize away multiple
__per_cpu_offset[smp_processor_id()] references.
Unfortunately (for my argument), you're right here: gcc doesn't cover
itself in glory. For example, the old case calculated "current" 4
times, the new case does it 6 times (if were recalculated every time,
it would be 9 times, so it's not completely hopeless).
So this version of the patch explicitly puts the kstat in a local
variable. It's smaller (and presumably faster) than the original:
clearly, noone was so anal about the original code.
Hope this helps!
Rusty.
--
Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
Name: Make kstat_this_cpu in terms of __get_cpu_var and use it
Author: Rusty Russell
Status: Tested on 2.5.74-bk1
D: kstat_this_cpu() is defined in terms of per_cpu instead of __get_cpu_var.
D: This patch changes that, and uses it everywhere appropriate. The sched.c
D: change puts it in a local variable, which helps gcc generate better code.
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.74-bk4/arch/i386/kernel/irq.c working-2.5.74-bk4-kstat-percpu/arch/i386/kernel/irq.c
--- linux-2.5.74-bk4/arch/i386/kernel/irq.c 2003-06-15 11:29:47.000000000 +1000
+++ working-2.5.74-bk4-kstat-percpu/arch/i386/kernel/irq.c 2003-07-07 14:03:14.000000000 +1000
@@ -416,7 +416,6 @@ asmlinkage unsigned int do_IRQ(struct pt
* handled by some other CPU. (or is disabled)
*/
int irq = regs.orig_eax & 0xff; /* high bits used in ret_from_ code */
- int cpu = smp_processor_id();
irq_desc_t *desc = irq_desc + irq;
struct irqaction * action;
unsigned int status;
@@ -437,7 +436,7 @@ asmlinkage unsigned int do_IRQ(struct pt
}
}
#endif
- kstat_cpu(cpu).irqs[irq]++;
+ kstat_this_cpu.irqs[irq]++;
spin_lock(&desc->lock);
desc->handler->ack(irq);
/*
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.74-bk4/include/linux/kernel_stat.h working-2.5.74-bk4-kstat-percpu/include/linux/kernel_stat.h
--- linux-2.5.74-bk4/include/linux/kernel_stat.h 2003-02-07 19:17:07.000000000 +1100
+++ working-2.5.74-bk4-kstat-percpu/include/linux/kernel_stat.h 2003-07-07 14:03:14.000000000 +1000
@@ -31,7 +31,8 @@ struct kernel_stat {
DECLARE_PER_CPU(struct kernel_stat, kstat);
#define kstat_cpu(cpu) per_cpu(kstat, cpu)
-#define kstat_this_cpu kstat_cpu(smp_processor_id())
+/* Must have preemption disabled for this to be meaningful. */
+#define kstat_this_cpu __get_cpu_var(kstat)
extern unsigned long nr_context_switches(void);
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.74-bk4/kernel/sched.c working-2.5.74-bk4-kstat-percpu/kernel/sched.c
--- linux-2.5.74-bk4/kernel/sched.c 2003-07-03 09:44:01.000000000 +1000
+++ working-2.5.74-bk4-kstat-percpu/kernel/sched.c 2003-07-07 15:18:20.000000000 +1000
@@ -1175,6 +1176,7 @@ DEFINE_PER_CPU(struct kernel_stat, kstat
void scheduler_tick(int user_ticks, int sys_ticks)
{
int cpu = smp_processor_id();
+ struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
runqueue_t *rq = this_rq();
task_t *p = current;
@@ -1184,19 +1186,19 @@ void scheduler_tick(int user_ticks, int
if (p == rq->idle) {
/* note: this timer irq context must be accounted for as well */
if (irq_count() - HARDIRQ_OFFSET >= SOFTIRQ_OFFSET)
- kstat_cpu(cpu).cpustat.system += sys_ticks;
+ cpustat->system += sys_ticks;
else if (atomic_read(&rq->nr_iowait) > 0)
- kstat_cpu(cpu).cpustat.iowait += sys_ticks;
+ cpustat->iowait += sys_ticks;
else
- kstat_cpu(cpu).cpustat.idle += sys_ticks;
+ cpustat->idle += sys_ticks;
rebalance_tick(rq, 1);
return;
}
if (TASK_NICE(p) > 0)
- kstat_cpu(cpu).cpustat.nice += user_ticks;
+ cpustat->nice += user_ticks;
else
- kstat_cpu(cpu).cpustat.user += user_ticks;
- kstat_cpu(cpu).cpustat.system += sys_ticks;
+ cpustat->user += user_ticks;
+ cpustat->system += sys_ticks;
/* Task might have expired already, but not scheduled off yet */
if (p->array != rq->active) {
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2003-07-07 5:40 UTC | newest]
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2003-07-04 1:53 [PATCH] kstat_this_cpu in terms of __get_cpu_var and use it Rusty Russell
2003-07-04 2:24 ` Linus Torvalds
2003-07-07 5:32 ` Rusty Russell
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