Re: [PATCH 3/4] cputime/powerpc/s390: make scaled cputime arch specific

Christian Borntraeger
2016-11-02T09:11:22Z

On 10/31/2016 01:36 PM, Stanislaw Gruszka wrote:
> Only s390 and powerpc have hardware facilities allowing to measure
> cputimes scaled by frequency. On all other architectures
> utimescaled/stimescaled are equal to utime/stime (however they are
> accounted separately).
>
> Patch remove {u,s}timescaled accounting on all architectures except
> powerpc and s390, where those values are explicitly accounted on proper
> places.

If we remove it everywhere else (and assuming that there are no users then)
I aks myself if we should remove this as well from s390.

We already had to optimize this because the initial code caused some
regressions (commit f341b8dff9 s390/vtime: limit MT scaling value updates).
The code still adds a multiply and a divide to do_account_vtime (and 2
multiplies and 2 divides into vtime_account_irq_enter) which is still
noticeable in perf annotate for switch intense workload.

Martin are you aware of any user of that values?

>
> Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
> ---
> arch/ia64/kernel/time.c | 4 +-
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/kernel/time.c | 6 +++-
> arch/s390/Kconfig | 1 +
> arch/s390/kernel/vtime.c | 9 ++++--
> include/linux/kernel_stat.h | 4 +-
> include/linux/sched.h | 23 ++++++++++++----
> kernel/fork.c | 2 +
> kernel/sched/cputime.c | 61 ++++++++++--------------------------------
> 9 files changed, 50 insertions(+), 61 deletions(-)
>
> diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
> index 6f892b9..021f44a 100644
> --- a/arch/ia64/kernel/time.c
> +++ b/arch/ia64/kernel/time.c
> @@ -68,7 +68,7 @@ void vtime_account_user(struct task_struct *tsk)
>
> if (ti->ac_utime) {
> delta_utime = cycle_to_cputime(ti->ac_utime);
> - account_user_time(tsk, delta_utime, delta_utime);
> + account_user_time(tsk, delta_utime);
> ti->ac_utime = 0;
> }
> }
> @@ -112,7 +112,7 @@ void vtime_account_system(struct task_struct *tsk)
> {
> cputime_t delta = vtime_delta(tsk);
>
> - account_system_time(tsk, 0, delta, delta);
> + account_system_time(tsk, 0, delta);
> }
> EXPORT_SYMBOL_GPL(vtime_account_system);
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 65fba4c..c7f120a 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -160,6 +160,7 @@ config PPC
> select HAVE_LIVEPATCH if HAVE_DYNAMIC_FTRACE_WITH_REGS
> select GENERIC_CPU_AUTOPROBE
> select HAVE_VIRT_CPU_ACCOUNTING
> + select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE
> select HAVE_ARCH_HARDENED_USERCOPY
> select HAVE_KERNEL_GZIP
>
> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
> index 8105198..be9751f 100644
> --- a/arch/powerpc/kernel/time.c
> +++ b/arch/powerpc/kernel/time.c
> @@ -358,7 +358,8 @@ void vtime_account_system(struct task_struct *tsk)
> unsigned long delta, sys_scaled, stolen;
>
> delta = vtime_delta(tsk, &sys_scaled, &stolen);
> - account_system_time(tsk, 0, delta, sys_scaled);
> + account_system_time(tsk, 0, delta);
> + tsk->stimescaled += sys_scaled;
> if (stolen)
> account_steal_time(stolen);
> }
> @@ -391,7 +392,8 @@ void vtime_account_user(struct task_struct *tsk)
> acct->user_time = 0;
> acct->user_time_scaled = 0;
> acct->utime_sspurr = 0;
> - account_user_time(tsk, utime, utimescaled);
> + account_user_time(tsk, utime);
> + tsk->utimescaled += utimescaled;
> }
>
> #ifdef CONFIG_PPC32
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 426481d..028f97b 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -171,6 +171,7 @@ config S390
> select SYSCTL_EXCEPTION_TRACE
> select TTY
> select VIRT_CPU_ACCOUNTING
> + select ARCH_HAS_SCALED_CPUTIME
> select VIRT_TO_BUS
> select HAVE_NMI
>
> diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
> index 856e30d..90eeb7c 100644
> --- a/arch/s390/kernel/vtime.c
> +++ b/arch/s390/kernel/vtime.c
> @@ -137,8 +137,10 @@ static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
> user_scaled = (user_scaled * mult) / div;
> system_scaled = (system_scaled * mult) / div;
> }
> - account_user_time(tsk, user, user_scaled);
> - account_system_time(tsk, hardirq_offset, system, system_scaled);
> + account_user_time(tsk, user);
> + tsk->utimescaled += user_scaled;
> + account_system_time(tsk, hardirq_offset, system)
> + tsk->stimescaled += system_scaled;
>
> steal = S390_lowcore.steal_timer;
> if ((s64) steal > 0) {
> @@ -202,7 +204,8 @@ void vtime_account_irq_enter(struct task_struct *tsk)
>
> system_scaled = (system_scaled * mult) / div;
> }
> - account_system_time(tsk, 0, system, system_scaled);
> + account_system_time(tsk, 0, system);
> + tsk->stimescaled += system_scaled;
>
> virt_timer_forward(system);
> }
> diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
> index 44fda64..00f7768 100644
> --- a/include/linux/kernel_stat.h
> +++ b/include/linux/kernel_stat.h
> @@ -78,8 +78,8 @@ static inline unsigned int kstat_cpu_irqs_sum(unsigned int cpu)
> return kstat_cpu(cpu).irqs_sum;
> }
>
> -extern void account_user_time(struct task_struct *, cputime_t, cputime_t);
> -extern void account_system_time(struct task_struct *, int, cputime_t, cputime_t);
> +extern void account_user_time(struct task_struct *, cputime_t);
> +extern void account_system_time(struct task_struct *, int, cputime_t);
> extern void account_steal_time(cputime_t);
> extern void account_idle_time(cputime_t);
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 348f51b..36a2c2e 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1627,7 +1627,10 @@ struct task_struct {
> int __user *set_child_tid; /* CLONE_CHILD_SETTID */
> int __user *clear_child_tid; /* CLONE_CHILD_CLEARTID */
>
> - cputime_t utime, stime, utimescaled, stimescaled;
> + cputime_t utime, stime;
> +#ifdef ARCH_HAS_SCALED_CPUTIME
> + cputime_t utimescaled, stimescaled;
> +#endif
> cputime_t gtime;
> struct prev_cputime prev_cputime;
> #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
> @@ -2220,8 +2223,6 @@ static inline void put_task_struct(struct task_struct *t)
> #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
> extern void task_cputime(struct task_struct *t,
> cputime_t *utime, cputime_t *stime);
> -extern void task_cputime_scaled(struct task_struct *t,
> - cputime_t *utimescaled, cputime_t *stimescaled);
> extern cputime_t task_gtime(struct task_struct *t);
> #else
> static inline void task_cputime(struct task_struct *t,
> @@ -2233,6 +2234,13 @@ static inline void task_cputime(struct task_struct *t,
> *stime = t->stime;
> }
>
> +static inline cputime_t task_gtime(struct task_struct *t)
> +{
> + return t->gtime;
> +}
> +#endif
> +
> +#ifdef ARCH_HAS_SCALED_CPUTIME
> static inline void task_cputime_scaled(struct task_struct *t,
> cputime_t *utimescaled,
> cputime_t *stimescaled)
> @@ -2242,12 +2250,15 @@ static inline void task_cputime_scaled(struct task_struct *t,
> if (stimescaled)
> *stimescaled = t->stimescaled;
> }
> -
> -static inline cputime_t task_gtime(struct task_struct *t)
> +#else
> +static inline void task_cputime_scaled(struct task_struct *t,
> + cputime_t *utimescaled,
> + cputime_t *stimescaled)
> {
> - return t->gtime;
> + task_cputime(t, utimescaled, stimescaled);
> }
> #endif
> +
> extern void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st);
> extern void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st);
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 623259f..dbc9f60 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1548,7 +1548,9 @@ static void posix_cpu_timers_init(struct task_struct *tsk)
> init_sigpending(&p->pending);
>
> p->utime = p->stime = p->gtime = 0;
> +#ifdef ARCH_HAS_SCALED_CPUTIME
> p->utimescaled = p->stimescaled = 0;
> +#endif
> prev_cputime_init(&p->prev_cputime);
>
> #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> index 3229c72..d427def 100644
> --- a/kernel/sched/cputime.c
> +++ b/kernel/sched/cputime.c
> @@ -128,16 +128,13 @@ static inline void task_group_account_field(struct task_struct *p, int index,
> * Account user cpu time to a process.
> * @p: the process that the cpu time gets accounted to
> * @cputime: the cpu time spent in user space since the last update
> - * @cputime_scaled: cputime scaled by cpu frequency
> */
> -void account_user_time(struct task_struct *p, cputime_t cputime,
> - cputime_t cputime_scaled)
> +void account_user_time(struct task_struct *p, cputime_t cputime)
> {
> int index;
>
> /* Add user time to process. */
> p->utime += cputime;
> - p->utimescaled += cputime_scaled;
> account_group_user_time(p, cputime);
>
> index = (task_nice(p) > 0) ? CPUTIME_NICE : CPUTIME_USER;
> @@ -153,16 +150,13 @@ void account_user_time(struct task_struct *p, cputime_t cputime,
> * Account guest cpu time to a process.
> * @p: the process that the cpu time gets accounted to
> * @cputime: the cpu time spent in virtual machine since the last update
> - * @cputime_scaled: cputime scaled by cpu frequency
> */
> -static void account_guest_time(struct task_struct *p, cputime_t cputime,
> - cputime_t cputime_scaled)
> +static void account_guest_time(struct task_struct *p, cputime_t cputime)
> {
> u64 *cpustat = kcpustat_this_cpu->cpustat;
>
> /* Add guest time to process. */
> p->utime += cputime;
> - p->utimescaled += cputime_scaled;
> account_group_user_time(p, cputime);
> p->gtime += cputime;
>
> @@ -180,16 +174,13 @@ static void account_guest_time(struct task_struct *p, cputime_t cputime,
> * Account system cpu time to a process and desired cpustat field
> * @p: the process that the cpu time gets accounted to
> * @cputime: the cpu time spent in kernel space since the last update
> - * @cputime_scaled: cputime scaled by cpu frequency
> - * @target_cputime64: pointer to cpustat field that has to be updated
> + * @index: pointer to cpustat field that has to be updated
> */
> static inline
> -void __account_system_time(struct task_struct *p, cputime_t cputime,
> - cputime_t cputime_scaled, int index)
> +void __account_system_time(struct task_struct *p, cputime_t cputime, int index)
> {
> /* Add system time to process. */
> p->stime += cputime;
> - p->stimescaled += cputime_scaled;
> account_group_system_time(p, cputime);
>
> /* Add system time to cpustat. */
> @@ -204,15 +195,14 @@ void __account_system_time(struct task_struct *p, cputime_t cputime,
> * @p: the process that the cpu time gets accounted to
> * @hardirq_offset: the offset to subtract from hardirq_count()
> * @cputime: the cpu time spent in kernel space since the last update
> - * @cputime_scaled: cputime scaled by cpu frequency
> */
> void account_system_time(struct task_struct *p, int hardirq_offset,
> - cputime_t cputime, cputime_t cputime_scaled)
> + cputime_t cputime)
> {
> int index;
>
> if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) {
> - account_guest_time(p, cputime, cputime_scaled);
> + account_guest_time(p, cputime);
> return;
> }
>
> @@ -223,7 +213,7 @@ void account_system_time(struct task_struct *p, int hardirq_offset,
> else
> index = CPUTIME_SYSTEM;
>
> - __account_system_time(p, cputime, cputime_scaled, index);
> + __account_system_time(p, cputime, index);
> }
>
> /*
> @@ -410,15 +400,15 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
> * So, we have to handle it separately here.
> * Also, p->stime needs to be updated for ksoftirqd.
> */
> - __account_system_time(p, cputime, cputime, CPUTIME_SOFTIRQ);
> + __account_system_time(p, cputime, CPUTIME_SOFTIRQ);
> } else if (user_tick) {
> - account_user_time(p, cputime, cputime);
> + account_user_time(p, cputime);
> } else if (p == rq->idle) {
> account_idle_time(cputime);
> } else if (p->flags & PF_VCPU) { /* System time or guest time */
> - account_guest_time(p, cputime, cputime);
> + account_guest_time(p, cputime);
> } else {
> - __account_system_time(p, cputime, cputime, CPUTIME_SYSTEM);
> + __account_system_time(p, cputime CPUTIME_SYSTEM);
> }
> }
>
> @@ -521,9 +511,9 @@ void account_process_tick(struct task_struct *p, int user_tick)
> cputime -= steal;
>
> if (user_tick)
> - account_user_time(p, cputime, cputime);
> + account_user_time(p, cputime);
> else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
> - account_system_time(p, HARDIRQ_OFFSET, cputime, cputime);
> + account_system_time(p, HARDIRQ_OFFSET, cputime);
> else
> account_idle_time(cputime);
> }
> @@ -744,7 +734,7 @@ static void __vtime_account_system(struct task_struct *tsk)
> {
> cputime_t delta_cpu = get_vtime_delta(tsk);
>
> - account_system_time(tsk, irq_count(), delta_cpu, delta_cpu);
> + account_system_time(tsk, irq_count(), delta_cpu);
> }
>
> void vtime_account_system(struct task_struct *tsk)
> @@ -765,7 +755,7 @@ void vtime_account_user(struct task_struct *tsk)
> tsk->vtime_snap_whence = VTIME_SYS;
> if (vtime_delta(tsk)) {
> delta_cpu = get_vtime_delta(tsk);
> - account_user_time(tsk, delta_cpu, delta_cpu);
> + account_user_time(tsk, delta_cpu);
> }
> write_seqcount_end(&tsk->vtime_seqcount);
> }
> @@ -921,25 +911,4 @@ void task_cputime(struct task_struct *t, cputime_t *utime, cputime_t *stime)
> if (stime)
> *stime += sdelta;
> }
> -
> -void task_cputime_scaled(struct task_struct *t,
> - cputime_t *utimescaled, cputime_t *stimescaled)
> -{
> - cputime_t udelta, sdelta;
> -
> - if (!vtime_accounting_enabled()) {
> - if (utimescaled)
> - *utimescaled = t->utimescaled;
> - if (stimescaled)
> - *stimescaled = t->stimescaled;
> - return;
> - }
> -
> - fetch_task_cputime(t, utimescaled, stimescaled,
> - &t->utimescaled, &t->stimescaled, &udelta, &sdelta);
> - if (utimescaled)
> - *utimescaled += udelta;
> - if (stimescaled)
> - *stimescaled += sdelta;
> -}
> #endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
>