sched/cputime: Rename vtime fields

The current "snapshot" based naming on vtime fields suggests we record
some past event but that's a low level picture of their actual purpose
which comes out blurry. The real point of these fields is to run a basic
state machine that tracks down cputime entry while switching between
contexts.

So lets reflect that with more meaningful names.

Tested-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1498756511-11714-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index e049526..3d53733 100644 (file)
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -171,8 +171,8 @@ extern struct cred init_cred;
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
 # define INIT_VTIME(tsk)                                               \
        .vtime_seqcount = SEQCNT_ZERO(tsk.vtime_seqcount),      \
-       .vtime_snap = 0,                                \
-       .vtime_snap_whence = VTIME_SYS,
+       .vtime_starttime = 0,                           \
+       .vtime_state = VTIME_SYS,
 #else
 # define INIT_VTIME(tsk)
 #endif

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9c4ca74..ff00164 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -689,7 +689,7 @@ struct task_struct {
        struct prev_cputime             prev_cputime;
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
        seqcount_t                      vtime_seqcount;
-       unsigned long long              vtime_snap;
+       unsigned long long              vtime_starttime;
        enum {
                /* Task is sleeping or running in a CPU with VTIME inactive: */
                VTIME_INACTIVE = 0,
@@ -697,7 +697,7 @@ struct task_struct {
                VTIME_USER,
                /* Task runs in kernelspace in a CPU with VTIME active: */
                VTIME_SYS,
-       } vtime_snap_whence;
+       } vtime_state;
 #endif
 
 #ifdef CONFIG_NO_HZ_FULL

diff --git a/kernel/fork.c b/kernel/fork.c
index e53770d..83c4f9b 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1638,8 +1638,8 @@ static __latent_entropy struct task_struct *copy_process(
 
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
        seqcount_init(&p->vtime_seqcount);
-       p->vtime_snap = 0;
-       p->vtime_snap_whence = VTIME_INACTIVE;
+       p->vtime_starttime = 0;
+       p->vtime_state = VTIME_INACTIVE;
 #endif
 
 #if defined(SPLIT_RSS_COUNTING)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index ab68927..8c64753 100644 (file)
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -683,10 +683,10 @@ static u64 vtime_delta(struct task_struct *tsk)
 {
        unsigned long now = READ_ONCE(jiffies);
 
-       if (time_before(now, (unsigned long)tsk->vtime_snap))
+       if (time_before(now, (unsigned long)tsk->vtime_starttime))
                return 0;
 
-       return jiffies_to_nsecs(now - tsk->vtime_snap);
+       return jiffies_to_nsecs(now - tsk->vtime_starttime);
 }
 
 static u64 get_vtime_delta(struct task_struct *tsk)
@@ -701,10 +701,10 @@ static u64 get_vtime_delta(struct task_struct *tsk)
         * elapsed time. Limit account_other_time to prevent rounding
         * errors from causing elapsed vtime to go negative.
         */
-       delta = jiffies_to_nsecs(now - tsk->vtime_snap);
+       delta = jiffies_to_nsecs(now - tsk->vtime_starttime);
        other = account_other_time(delta);
-       WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);
-       tsk->vtime_snap = now;
+       WARN_ON_ONCE(tsk->vtime_state == VTIME_INACTIVE);
+       tsk->vtime_starttime = now;
 
        return delta - other;
 }
@@ -746,7 +746,7 @@ void vtime_guest_enter(struct task_struct *tsk)
 {
        /*
         * The flags must be updated under the lock with
-        * the vtime_snap flush and update.
+        * the vtime_starttime flush and update.
         * That enforces a right ordering and update sequence
         * synchronization against the reader (task_gtime())
         * that can thus safely catch up with a tickless delta.
@@ -776,12 +776,12 @@ void vtime_account_idle(struct task_struct *tsk)
 void arch_vtime_task_switch(struct task_struct *prev)
 {
        write_seqcount_begin(&prev->vtime_seqcount);
-       prev->vtime_snap_whence = VTIME_INACTIVE;
+       prev->vtime_state = VTIME_INACTIVE;
        write_seqcount_end(&prev->vtime_seqcount);
 
        write_seqcount_begin(&current->vtime_seqcount);
-       current->vtime_snap_whence = VTIME_SYS;
-       current->vtime_snap = jiffies;
+       current->vtime_state = VTIME_SYS;
+       current->vtime_starttime = jiffies;
        write_seqcount_end(&current->vtime_seqcount);
 }
 
@@ -791,8 +791,8 @@ void vtime_init_idle(struct task_struct *t, int cpu)
 
        local_irq_save(flags);
        write_seqcount_begin(&t->vtime_seqcount);
-       t->vtime_snap_whence = VTIME_SYS;
-       t->vtime_snap = jiffies;
+       t->vtime_state = VTIME_SYS;
+       t->vtime_starttime = jiffies;
        write_seqcount_end(&t->vtime_seqcount);
        local_irq_restore(flags);
 }
@@ -809,7 +809,7 @@ u64 task_gtime(struct task_struct *t)
                seq = read_seqcount_begin(&t->vtime_seqcount);
 
                gtime = t->gtime;
-               if (t->vtime_snap_whence == VTIME_SYS && t->flags & PF_VCPU)
+               if (t->vtime_state == VTIME_SYS && t->flags & PF_VCPU)
                        gtime += vtime_delta(t);
 
        } while (read_seqcount_retry(&t->vtime_seqcount, seq));
@@ -840,7 +840,7 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
                *stime = t->stime;
 
                /* Task is sleeping, nothing to add */
-               if (t->vtime_snap_whence == VTIME_INACTIVE || is_idle_task(t))
+               if (t->vtime_state == VTIME_INACTIVE || is_idle_task(t))
                        continue;
 
                delta = vtime_delta(t);
@@ -849,9 +849,9 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
                 * Task runs either in user or kernel space, add pending nohz time to
                 * the right place.
                 */
-               if (t->vtime_snap_whence == VTIME_USER || t->flags & PF_VCPU)
+               if (t->vtime_state == VTIME_USER || t->flags & PF_VCPU)
                        *utime += delta;
-               else if (t->vtime_snap_whence == VTIME_SYS)
+               else if (t->vtime_state == VTIME_SYS)
                        *stime += delta;
        } while (read_seqcount_retry(&t->vtime_seqcount, seq));
 }