[PATCH/RFC 3/4, second shot]Introduce "account_guest_time"

Laurent Vivier
2007-08-17T11:51:49Z

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This is another way to compute guest time... I remove the "account modifiers"
mechanism and call directly account_guest_time() from account_system_time().
account_system_time() computes user, system and guest times according value
accumulated in vtime (a ktime_t) in task_struct by the virtual machine.
--
------------- Laurent.Vivier-6ktuUTfB/bM@public.gmane.org --------------
"Software is hard" - Donald Knuth

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Index: kvm/include/linux/sched.h
===================================================================
--- kvm.orig/include/linux/sched.h 2007-08-17 10:18:53.000000000 +0200
+++ kvm/include/linux/sched.h 2007-08-17 12:33:22.000000000 +0200
@@ -1192,6 +1192,9 @@
#ifdef CONFIG_FAULT_INJECTION
int make_it_fail;
#endif
+#ifdef CONFIG_GUEST_ACCOUNTING
+ ktime_t vtime;
+#endif
};

/*
Index: kvm/kernel/sched.c
===================================================================
--- kvm.orig/kernel/sched.c 2007-08-17 10:18:53.000000000 +0200
+++ kvm/kernel/sched.c 2007-08-17 12:33:07.000000000 +0200
@@ -3233,6 +3233,37 @@
cpustat->user = cputime64_add(cpustat->user, tmp);
}

+#ifdef CONFIG_GUEST_ACCOUNTING
+/*
+ * Account guest time to a process
+ * @p: the process that the cpu time gets accounted to
+ * @cputime: the cpu time spent in kernel space since the last update
+ */
+
+static cputime_t account_guest_time(struct task_struct *p, cputime_t cputime)
+{
+ struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
+ ktime_t kmsec = ktime_set(0, NSEC_PER_MSEC);
+ cputime_t cmsec = msecs_to_cputime(1);
+
+ while ((ktime_to_ns(p->vtime) >= NSEC_PER_MSEC) &&
+ (cputime_to_msecs(cputime) >= 1)) {
+ p->vtime = ktime_sub(p->vtime, kmsec);
+ p->utime = cputime_add(p->utime, cmsec);
+ p->gtime = cputime_add(p->gtime, cmsec);
+
+ cpustat->guest = cputime64_add(cpustat->guest,
+ cputime_to_cputime64(cmsec));
+ cpustat->user = cputime64_add(cpustat->user,
+ cputime_to_cputime64(cmsec));
+
+ cputime = cputime_sub(cputime, cmsec);
+ }
+
+ return cputime;
+}
+#endif
+
/*
* Account system cpu time to a process.
* @p: the process that the cpu time gets accounted to
@@ -3246,6 +3277,10 @@
struct rq *rq = this_rq();
cputime64_t tmp;

+#ifdef CONFIG_GUEST_ACCOUNTING
+ cputime = account_guest_time(p, cputime);
+#endif
+
p->stime = cputime_add(p->stime, cputime);

/* Add system time to cpustat. */

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