[Xen-ia64-devel] [PATCH 10/15] ia64/pv_ops/xen/pv_time_ops: implement sched_clock.

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

paravirtualize sched_clock.

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
---
 arch/ia64/xen/Kconfig |    1 +
 arch/ia64/xen/time.c  |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/arch/ia64/xen/Kconfig b/arch/ia64/xen/Kconfig
index f1683a2..48839da 100644
--- a/arch/ia64/xen/Kconfig
+++ b/arch/ia64/xen/Kconfig
@@ -8,6 +8,7 @@ config XEN
        depends on PARAVIRT && MCKINLEY && IA64_PAGE_SIZE_16KB && EXPERIMENTAL
        select XEN_XENCOMM
        select NO_IDLE_HZ
+       select HAVE_UNSTABLE_SCHED_CLOCK
 
        # those are required to save/restore.
        select ARCH_SUSPEND_POSSIBLE
diff --git a/arch/ia64/xen/time.c b/arch/ia64/xen/time.c
index d15a94c..c85d319 100644
--- a/arch/ia64/xen/time.c
+++ b/arch/ia64/xen/time.c
@@ -175,10 +175,58 @@ static void xen_itc_jitter_data_reset(void)
        } while (unlikely(ret != lcycle));
 }
 
+/* based on xen_sched_clock() in arch/x86/xen/time.c. */
+/*
+ * This relies on HAVE_UNSTABLE_SCHED_CLOCK. If it can't be defined,
+ * something similar logic should be implemented here.
+ */
+/*
+ * Xen sched_clock implementation.  Returns the number of unstolen
+ * nanoseconds, which is nanoseconds the VCPU spent in RUNNING+BLOCKED
+ * states.
+ */
+static unsigned long long xen_sched_clock(void)
+{
+       struct vcpu_runstate_info runstate;
+
+       unsigned long long now;
+       unsigned long long offset;
+       unsigned long long ret;
+
+       /*
+        * Ideally sched_clock should be called on a per-cpu basis
+        * anyway, so preempt should already be disabled, but that's
+        * not current practice at the moment.
+        */
+       preempt_disable();
+
+       /*
+        * both ia64_native_sched_clock() and xen's runstate are
+        * based on mAR.ITC. So difference of them makes sense.
+        */
+       now = ia64_native_sched_clock();
+
+       get_runstate_snapshot(&runstate);
+
+       WARN_ON(runstate.state != RUNSTATE_running);
+
+       offset = 0;
+       if (now > runstate.state_entry_time)
+               offset = now - runstate.state_entry_time;
+       ret = runstate.time[RUNSTATE_blocked] +
+               runstate.time[RUNSTATE_running] +
+               offset;
+
+       preempt_enable();
+
+       return ret;
+}
+
 struct pv_time_ops xen_time_ops __initdata = {
        .init_missing_ticks_accounting  = xen_init_missing_ticks_accounting,
        .do_steal_accounting            = xen_do_steal_accounting,
        .clocksource_resume             = xen_itc_jitter_data_reset,
+       .sched_clock                    = xen_sched_clock,
 };
 
 /* Called after suspend, to resume time.  */
-- 
1.6.0.2


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