lkml.org 
[lkml]   [2018]   [Jun]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v4 1/2] powerpc/time: Only set CONFIG_ARCH_HAS_SCALED_CPUTIME on PPC64
Date
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 in 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 5% 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:

~# perf stat chrt -f 98 ./sched 100000

Performance counter stats for 'chrt -f 98 ./sched 100000':

8622.166272 task-clock (msec) # 0.955 CPUs utilized
200027 context-switches # 0.023 M/sec

After the patch:

~# perf stat chrt -f 98 ./sched 100000

Performance counter stats for 'chrt -f 98 ./sched 100000':

8207.090048 task-clock (msec) # 0.958 CPUs utilized
200025 context-switches # 0.024 M/sec

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
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/Kconfig | 2 +-
arch/powerpc/include/asm/accounting.h | 4 ++
arch/powerpc/include/asm/cputime.h | 1 -
arch/powerpc/kernel/time.c | 111 +++++++++++++++++++++-------------
arch/powerpc/xmon/xmon.c | 4 ++
5 files changed, 77 insertions(+), 45 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index b62a16e2c7cc..735398fd390d 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -142,7 +142,7 @@ config PPC
select ARCH_HAS_PHYS_TO_DMA
select ARCH_HAS_PMEM_API if PPC64
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 bc4903badb3f..a48c7b5e5cf9 100644
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -62,7 +62,6 @@ 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 70f145e02487..7a9f4e2f22c8 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -171,19 +171,6 @@ static void calc_cputime_factors(void)
__cputime_usec_factor = res.result_low;
}

-/*
- * 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)
-{
- if (cpu_has_feature(CPU_FTR_SPURR))
- return mfspr(SPRN_SPURR);
- if (cpu_has_feature(CPU_FTR_PURR))
- return mfspr(SPRN_PURR);
- return tb;
-}
-
#ifdef CONFIG_PPC_SPLPAR

/*
@@ -277,30 +264,27 @@ static inline u64 calculate_stolen_time(u64 stop_tb)

#endif /* CONFIG_PPC_SPLPAR */

-/*
- * 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;
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
+ unsigned long nowscaled, deltascaled;
unsigned long utime, utime_scaled;
- struct cpu_accounting_data *acct = get_accounting(tsk);
+ unsigned long stime_scaled;

- WARN_ON_ONCE(!irqs_disabled());
+ /*
+ * Read the SPURR on systems that have it, otherwise the PURR,
+ * or if that doesn't exist user the timebase value passed in.
+ */
+ if (cpu_has_feature(CPU_FTR_SPURR))
+ nowscaled = mfspr(SPRN_SPURR);
+ else if (cpu_has_feature(CPU_FTR_PURR))
+ nowscaled = mfspr(SPRN_PURR);
+ else
+ nowscaled = now;

- 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 +298,46 @@ 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;
+#else
+ return 0;
+#endif
+}
+
+/*
+ * 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)
+{
+ unsigned long now;
+ unsigned long 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;
}

@@ -341,7 +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;
@@ -350,7 +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);
@@ -364,6 +380,21 @@ 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)
+{
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
+ 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;
+#endif
+}
+
/*
* Account the whole cputime accumulated in the paca
* Must be called with interrupts disabled.
@@ -378,9 +409,6 @@ 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 +421,6 @@ 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),
@@ -404,15 +430,14 @@ void vtime_flush(struct task_struct *tsk)
CPUTIME_SOFTIRQ);

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;
+
+ vtime_flush_scaled(tsk, acct);
}

#else /* ! CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 47166ad2a669..b1e551d40ee1 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -2443,11 +2443,15 @@ 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
\
 
 \ /
  Last update: 2018-06-06 16:21    [W:0.026 / U:1.968 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site