path: root/arch
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authorSuresh Siddha <suresh.b.siddha@intel.com>2010-08-19 17:03:38 -0700
committerIngo Molnar <mingo@elte.hu>2010-08-20 14:59:02 +0200
commitcd7240c0b900eb6d690ccee088a6c9b46dae815a (patch)
tree0a1ed10298a2bb2c9d6010c4d03a7f9508bdcba6 /arch
parent861d034ee814917a83bd5de4b26e3b8336ddeeb8 (diff)
x86, tsc, sched: Recompute cyc2ns_offset's during resume from sleep states
TSC's get reset after suspend/resume (even on cpu's with invariant TSC which runs at a constant rate across ACPI P-, C- and T-states). And in some systems BIOS seem to reinit TSC to arbitrary large value (still sync'd across cpu's) during resume. This leads to a scenario of scheduler rq->clock (sched_clock_cpu()) less than rq->age_stamp (introduced in 2.6.32). This leads to a big value returned by scale_rt_power() and the resulting big group power set by the update_group_power() is causing improper load balancing between busy and idle cpu's after suspend/resume. This resulted in multi-threaded workloads (like kernel-compilation) go slower after suspend/resume cycle on core i5 laptops. Fix this by recomputing cyc2ns_offset's during resume, so that sched_clock() continues from the point where it was left off during suspend. Reported-by: Florian Pritz <flo@xssn.at> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Cc: <stable@kernel.org> # [v2.6.32+] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1282262618.2675.24.camel@sbsiddha-MOBL3.sc.intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
3 files changed, 42 insertions, 0 deletions
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index c0427295e8f..1ca132fc0d0 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -59,5 +59,7 @@ extern void check_tsc_sync_source(int cpu);
extern void check_tsc_sync_target(void);
extern int notsc_setup(char *);
+extern void save_sched_clock_state(void);
+extern void restore_sched_clock_state(void);
#endif /* _ASM_X86_TSC_H */
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index ce8e5023933..d632934cb63 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -626,6 +626,44 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
+static unsigned long long cyc2ns_suspend;
+void save_sched_clock_state(void)
+ if (!sched_clock_stable)
+ return;
+ cyc2ns_suspend = sched_clock();
+ * Even on processors with invariant TSC, TSC gets reset in some the
+ * ACPI system sleep states. And in some systems BIOS seem to reinit TSC to
+ * arbitrary value (still sync'd across cpu's) during resume from such sleep
+ * states. To cope up with this, recompute the cyc2ns_offset for each cpu so
+ * that sched_clock() continues from the point where it was left off during
+ * suspend.
+ */
+void restore_sched_clock_state(void)
+ unsigned long long offset;
+ unsigned long flags;
+ int cpu;
+ if (!sched_clock_stable)
+ return;
+ local_irq_save(flags);
+ get_cpu_var(cyc2ns_offset) = 0;
+ offset = cyc2ns_suspend - sched_clock();
+ for_each_possible_cpu(cpu)
+ per_cpu(cyc2ns_offset, cpu) = offset;
+ local_irq_restore(flags);
/* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index e7e8c5f5495..87bb35e34ef 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -113,6 +113,7 @@ static void __save_processor_state(struct saved_context *ctxt)
void save_processor_state(void)
+ save_sched_clock_state();
#ifdef CONFIG_X86_32
@@ -229,6 +230,7 @@ static void __restore_processor_state(struct saved_context *ctxt)
void restore_processor_state(void)
+ restore_sched_clock_state();
#ifdef CONFIG_X86_32