linux-kernel - [tip:sched/core] sched/cputime: Add steal time support to full dynticks CPU time accounting

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Date:	Tue, 14 Jun 2016 04:27:04 -0700
From:	tip-bot for Wanpeng Li <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	efault@....de, wanpeng.li@...mail.com, riel@...hat.com,
	tglx@...utronix.de, rkrcmar@...hat.com, pbonzini@...hat.com,
	torvalds@...ux-foundation.org, fweisbec@...il.com,
	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, hpa@...or.com
Subject: [tip:sched/core] sched/cputime: Add steal time support to full
 dynticks CPU time accounting

Commit-ID:  807e5b80687c06715d62df51a5473b231e3e8b15
Gitweb:     http://git.kernel.org/tip/807e5b80687c06715d62df51a5473b231e3e8b15
Author:     Wanpeng Li <wanpeng.li@...mail.com>
AuthorDate: Mon, 13 Jun 2016 18:32:46 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 14 Jun 2016 11:13:16 +0200

sched/cputime: Add steal time support to full dynticks CPU time accounting

This patch adds guest steal-time support to full dynticks CPU
time accounting. After the following commit:

ff9a9b4c4334 ("sched, time: Switch VIRT_CPU_ACCOUNTING_GEN to jiffy granularity")

... time sampling became jiffy based, even if we do the sampling from the
context tracking code, so steal_account_process_tick() can be reused
to account how many 'ticks' are stolen-time, after the last accumulation.

Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Paolo Bonzini <pbonzini@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1465813966-3116-4-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/cputime.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 75f98c5..3d60e5d 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -257,7 +257,7 @@ void account_idle_time(cputime_t cputime)
 		cpustat[CPUTIME_IDLE] += (__force u64) cputime;
 }
 
-static __always_inline bool steal_account_process_tick(void)
+static __always_inline unsigned long steal_account_process_tick(unsigned long max_jiffies)
 {
 #ifdef CONFIG_PARAVIRT
 	if (static_key_false(&paravirt_steal_enabled)) {
@@ -272,14 +272,14 @@ static __always_inline bool steal_account_process_tick(void)
 		 * time in jiffies. Lets cast the result to jiffies
 		 * granularity and account the rest on the next rounds.
 		 */
-		steal_jiffies = nsecs_to_jiffies(steal);
+		steal_jiffies = min(nsecs_to_jiffies(steal), max_jiffies);
 		this_rq()->prev_steal_time += jiffies_to_nsecs(steal_jiffies);
 
 		account_steal_time(jiffies_to_cputime(steal_jiffies));
 		return steal_jiffies;
 	}
 #endif
-	return false;
+	return 0;
 }
 
 /*
@@ -346,7 +346,7 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
 	u64 cputime = (__force u64) cputime_one_jiffy;
 	u64 *cpustat = kcpustat_this_cpu->cpustat;
 
-	if (steal_account_process_tick())
+	if (steal_account_process_tick(ULONG_MAX))
 		return;
 
 	cputime *= ticks;
@@ -477,7 +477,7 @@ void account_process_tick(struct task_struct *p, int user_tick)
 		return;
 	}
 
-	if (steal_account_process_tick())
+	if (steal_account_process_tick(ULONG_MAX))
 		return;
 
 	if (user_tick)
@@ -681,12 +681,14 @@ static cputime_t vtime_delta(struct task_struct *tsk)
 static cputime_t get_vtime_delta(struct task_struct *tsk)
 {
 	unsigned long now = READ_ONCE(jiffies);
-	unsigned long delta = now - tsk->vtime_snap;
+	unsigned long delta_jiffies, steal_jiffies;
 
+	delta_jiffies = now - tsk->vtime_snap;
+	steal_jiffies = steal_account_process_tick(delta_jiffies);
 	WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);
 	tsk->vtime_snap = now;
 
-	return jiffies_to_cputime(delta);
+	return jiffies_to_cputime(delta_jiffies - steal_jiffies);
 }
 
 static void __vtime_account_system(struct task_struct *tsk)