scaled cputime is only meaningfull when the processor has
SPURR and/or PURR, which means only on PPC64.
In preparation of the following patch that will remove
CONFIG_ARCH_HAS_SCALED_CPUTIME on PPC32, this patch moves
all scaled cputing accounting logic into dedicated functions.
This patch doesn't change any functionality. It's only code
reorganisation.
Signed-off-by: Christophe Leroy <[email protected]>
---
v5:
- v4 patch split in two patches. First part isolates scaled cputime accounting
in dedicated functions, second part activates it only on PPC64.
- read_spurr() kept as a separate function.
v4:
- Using the correct symbol CONFIG_ARCH_HAS_SCALED_CPUTIME instead of ARCH_HAS_SCALED_CPUTIME
- Grouped CONFIG_ARCH_HAS_SCALED_CPUTIME related code in dedicated functions to reduce the number of #ifdefs
- Integrated read_spurr() directly into the related function.
v3: Rebased following modifications in xmon.c
v2: added ifdefs in xmon to fix compilation error
arch/powerpc/kernel/time.c | 69 +++++++++++++++++++++++++++++-----------------
1 file changed, 43 insertions(+), 26 deletions(-)
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 70f145e02487..6196bd7393a3 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -281,26 +281,16 @@ static inline u64 calculate_stolen_time(u64 stop_tb)
* Account time for a transition between system, hard irq
* or soft irq state.
*/
-static unsigned long vtime_delta(struct task_struct *tsk,
- unsigned long *stime_scaled,
- unsigned long *steal_time)
+static unsigned long vtime_delta_scaled(struct cpu_accounting_data *acct,
+ unsigned long now, unsigned long stime)
{
- unsigned long now, nowscaled, deltascaled;
- unsigned long stime;
+ unsigned long stime_scaled;
+ unsigned long nowscaled, deltascaled;
unsigned long utime, utime_scaled;
- struct cpu_accounting_data *acct = get_accounting(tsk);
- WARN_ON_ONCE(!irqs_disabled());
-
- now = mftb();
nowscaled = read_spurr(now);
- stime = now - acct->starttime;
- acct->starttime = now;
deltascaled = nowscaled - acct->startspurr;
acct->startspurr = nowscaled;
-
- *steal_time = calculate_stolen_time(now);
-
utime = acct->utime - acct->utime_sspurr;
acct->utime_sspurr = acct->utime;
@@ -314,18 +304,38 @@ static unsigned long vtime_delta(struct task_struct *tsk,
* the user ticks get saved up in paca->user_time_scaled to be
* used by account_process_tick.
*/
- *stime_scaled = stime;
+ stime_scaled = stime;
utime_scaled = utime;
if (deltascaled != stime + utime) {
if (utime) {
- *stime_scaled = deltascaled * stime / (stime + utime);
- utime_scaled = deltascaled - *stime_scaled;
+ stime_scaled = deltascaled * stime / (stime + utime);
+ utime_scaled = deltascaled - stime_scaled;
} else {
- *stime_scaled = deltascaled;
+ stime_scaled = deltascaled;
}
}
acct->utime_scaled += utime_scaled;
+ return stime_scaled;
+}
+
+static unsigned long vtime_delta(struct task_struct *tsk,
+ unsigned long *stime_scaled,
+ unsigned long *steal_time)
+{
+ unsigned long now, stime;
+ struct cpu_accounting_data *acct = get_accounting(tsk);
+
+ WARN_ON_ONCE(!irqs_disabled());
+
+ now = mftb();
+ stime = now - acct->starttime;
+ acct->starttime = now;
+
+ *stime_scaled = vtime_delta_scaled(acct, now, stime);
+
+ *steal_time = calculate_stolen_time(now);
+
return stime;
}
@@ -364,6 +374,19 @@ void vtime_account_idle(struct task_struct *tsk)
acct->idle_time += stime + steal_time;
}
+static void vtime_flush_scaled(struct task_struct *tsk,
+ struct cpu_accounting_data *acct)
+{
+ if (acct->utime_scaled)
+ tsk->utimescaled += cputime_to_nsecs(acct->utime_scaled);
+ if (acct->stime_scaled)
+ tsk->stimescaled += cputime_to_nsecs(acct->stime_scaled);
+
+ acct->utime_scaled = 0;
+ acct->utime_sspurr = 0;
+ acct->stime_scaled = 0;
+}
+
/*
* Account the whole cputime accumulated in the paca
* Must be called with interrupts disabled.
@@ -378,9 +401,6 @@ void vtime_flush(struct task_struct *tsk)
if (acct->utime)
account_user_time(tsk, cputime_to_nsecs(acct->utime));
- if (acct->utime_scaled)
- tsk->utimescaled += cputime_to_nsecs(acct->utime_scaled);
-
if (acct->gtime)
account_guest_time(tsk, cputime_to_nsecs(acct->gtime));
@@ -393,8 +413,6 @@ void vtime_flush(struct task_struct *tsk)
if (acct->stime)
account_system_index_time(tsk, cputime_to_nsecs(acct->stime),
CPUTIME_SYSTEM);
- if (acct->stime_scaled)
- tsk->stimescaled += cputime_to_nsecs(acct->stime_scaled);
if (acct->hardirq_time)
account_system_index_time(tsk, cputime_to_nsecs(acct->hardirq_time),
@@ -403,14 +421,13 @@ void vtime_flush(struct task_struct *tsk)
account_system_index_time(tsk, cputime_to_nsecs(acct->softirq_time),
CPUTIME_SOFTIRQ);
+ vtime_flush_scaled(tsk, acct);
+
acct->utime = 0;
- acct->utime_scaled = 0;
- acct->utime_sspurr = 0;
acct->gtime = 0;
acct->steal_time = 0;
acct->idle_time = 0;
acct->stime = 0;
- acct->stime_scaled = 0;
acct->hardirq_time = 0;
acct->softirq_time = 0;
}
--
2.13.3
If CONFIG_PPC_SPLPAR is not selected, steal_time will always
be NUL, so accounting it is pointless
Signed-off-by: Christophe Leroy <[email protected]>
---
v5: moved the change to the original localtion
v4: removed the check in vtime_account_system(), the compiler removes the code regardless.
v3: new
arch/powerpc/kernel/time.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 3b03731221c1..b0f5cc491f8b 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -412,8 +412,10 @@ void vtime_flush(struct task_struct *tsk)
if (acct->gtime)
account_guest_time(tsk, cputime_to_nsecs(acct->gtime));
- if (acct->steal_time)
+ if (IS_ENABLED(CONFIG_PPC_SPLPAR) && acct->steal_time) {
account_steal_time(cputime_to_nsecs(acct->steal_time));
+ acct->steal_time = 0;
+ }
if (acct->idle_time)
account_idle_time(cputime_to_nsecs(acct->idle_time));
@@ -433,7 +435,6 @@ void vtime_flush(struct task_struct *tsk)
acct->utime = 0;
acct->gtime = 0;
- acct->steal_time = 0;
acct->idle_time = 0;
acct->stime = 0;
acct->hardirq_time = 0;
--
2.13.3
scaled cputime is only meaningfull when the processor has
SPURR and/or PURR, which means only on PPC64.
Removing it on PPC32 significantly reduces the size of
vtime_account_system() and vtime_account_idle() on an 8xx:
Before:
00000000 l F .text 000000a8 vtime_delta
00000280 g F .text 0000010c vtime_account_system
0000038c g F .text 00000048 vtime_account_idle
After:
(vtime_delta gets inlined inside the two functions)
000001d8 g F .text 000000a0 vtime_account_system
00000278 g F .text 00000038 vtime_account_idle
In terms of performance, we also get approximatly 7% improvement on
task switch. The following small benchmark app is run with perf stat:
void *thread(void *arg)
{
int i;
for (i = 0; i < atoi((char*)arg); i++)
pthread_yield();
}
int main(int argc, char **argv)
{
pthread_t th1, th2;
pthread_create(&th1, NULL, thread, argv[1]);
pthread_create(&th2, NULL, thread, argv[1]);
pthread_join(th1, NULL);
pthread_join(th2, NULL);
return 0;
}
Before the patch:
Performance counter stats for 'chrt -f 98 ./sched 100000' (50 runs):
8228.476465 task-clock (msec) # 0.954 CPUs utilized ( +- 0.23% )
200004 context-switches # 0.024 M/sec ( +- 0.00% )
After the patch:
Performance counter stats for 'chrt -f 98 ./sched 100000' (50 runs):
7649.070444 task-clock (msec) # 0.955 CPUs utilized ( +- 0.27% )
200004 context-switches # 0.026 M/sec ( +- 0.00% )
Signed-off-by: Christophe Leroy <[email protected]>
---
v5: New (previous patch splitted in two parts)
arch/powerpc/Kconfig | 2 +-
arch/powerpc/include/asm/accounting.h | 4 ++++
arch/powerpc/include/asm/cputime.h | 1 -
arch/powerpc/kernel/time.c | 12 ++++++++++--
arch/powerpc/xmon/xmon.c | 4 ++++
5 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 5eb4d969afbf..1f5ce708a650 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -137,7 +137,7 @@ config PPC
select ARCH_HAS_PMEM_API if PPC64
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_MEMBARRIER_CALLBACKS
- select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE
+ select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE && PPC64
select ARCH_HAS_SG_CHAIN
select ARCH_HAS_STRICT_KERNEL_RWX if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
diff --git a/arch/powerpc/include/asm/accounting.h b/arch/powerpc/include/asm/accounting.h
index 3abcf98ed2e0..c607c5d835cc 100644
--- a/arch/powerpc/include/asm/accounting.h
+++ b/arch/powerpc/include/asm/accounting.h
@@ -15,8 +15,10 @@ struct cpu_accounting_data {
/* Accumulated cputime values to flush on ticks*/
unsigned long utime;
unsigned long stime;
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
unsigned long utime_scaled;
unsigned long stime_scaled;
+#endif
unsigned long gtime;
unsigned long hardirq_time;
unsigned long softirq_time;
@@ -25,8 +27,10 @@ struct cpu_accounting_data {
/* Internal counters */
unsigned long starttime; /* TB value snapshot */
unsigned long starttime_user; /* TB value on exit to usermode */
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
unsigned long startspurr; /* SPURR value snapshot */
unsigned long utime_sspurr; /* ->user_time when ->startspurr set */
+#endif
};
#endif
diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
index 133672744b2e..ae73dc8da2d4 100644
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -61,7 +61,6 @@ static inline void arch_vtime_task_switch(struct task_struct *prev)
struct cpu_accounting_data *acct0 = get_accounting(prev);
acct->starttime = acct0->starttime;
- acct->startspurr = acct0->startspurr;
}
#endif
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 6196bd7393a3..3b03731221c1 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -175,7 +175,7 @@ static void calc_cputime_factors(void)
* Read the SPURR on systems that have it, otherwise the PURR,
* or if that doesn't exist return the timebase value passed in.
*/
-static unsigned long read_spurr(unsigned long tb)
+static inline unsigned long read_spurr(unsigned long tb)
{
if (cpu_has_feature(CPU_FTR_SPURR))
return mfspr(SPRN_SPURR);
@@ -284,7 +284,8 @@ static inline u64 calculate_stolen_time(u64 stop_tb)
static unsigned long vtime_delta_scaled(struct cpu_accounting_data *acct,
unsigned long now, unsigned long stime)
{
- unsigned long stime_scaled;
+ unsigned long stime_scaled = 0;
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
unsigned long nowscaled, deltascaled;
unsigned long utime, utime_scaled;
@@ -315,6 +316,7 @@ static unsigned long vtime_delta_scaled(struct cpu_accounting_data *acct,
}
}
acct->utime_scaled += utime_scaled;
+#endif
return stime_scaled;
}
@@ -351,7 +353,9 @@ void vtime_account_system(struct task_struct *tsk)
if ((tsk->flags & PF_VCPU) && !irq_count()) {
acct->gtime += stime;
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
acct->utime_scaled += stime_scaled;
+#endif
} else {
if (hardirq_count())
acct->hardirq_time += stime;
@@ -360,7 +364,9 @@ void vtime_account_system(struct task_struct *tsk)
else
acct->stime += stime;
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
acct->stime_scaled += stime_scaled;
+#endif
}
}
EXPORT_SYMBOL_GPL(vtime_account_system);
@@ -377,6 +383,7 @@ void vtime_account_idle(struct task_struct *tsk)
static void vtime_flush_scaled(struct task_struct *tsk,
struct cpu_accounting_data *acct)
{
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
if (acct->utime_scaled)
tsk->utimescaled += cputime_to_nsecs(acct->utime_scaled);
if (acct->stime_scaled)
@@ -385,6 +392,7 @@ static void vtime_flush_scaled(struct task_struct *tsk,
acct->utime_scaled = 0;
acct->utime_sspurr = 0;
acct->stime_scaled = 0;
+#endif
}
/*
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index c7324e8469ee..cb7d1ce029c6 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -2442,11 +2442,15 @@ static void dump_one_paca(int cpu)
DUMP(p, accounting.utime, "%#-*lx");
DUMP(p, accounting.stime, "%#-*lx");
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
DUMP(p, accounting.utime_scaled, "%#-*lx");
+#endif
DUMP(p, accounting.starttime, "%#-*lx");
DUMP(p, accounting.starttime_user, "%#-*lx");
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
DUMP(p, accounting.startspurr, "%#-*lx");
DUMP(p, accounting.utime_sspurr, "%#-*lx");
+#endif
DUMP(p, accounting.steal_time, "%#-*lx");
#undef DUMP
--
2.13.3
On Thu, 2018-08-02 at 07:53:57 UTC, Christophe Leroy wrote:
> scaled cputime is only meaningfull when the processor has
> SPURR and/or PURR, which means only on PPC64.
>
> In preparation of the following patch that will remove
> CONFIG_ARCH_HAS_SCALED_CPUTIME on PPC32, this patch moves
> all scaled cputing accounting logic into dedicated functions.
>
> This patch doesn't change any functionality. It's only code
> reorganisation.
>
> Signed-off-by: Christophe Leroy <[email protected]>
Series applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/b38a181c11d0b5e84b40732dbb06cc
cheers