- Speed up boot - skip unnecessary clock calibration
PATCH 1/1 - Speed up boot - skip unnecessary clock calibration
Skip clock calibration if cpu being brought online is exactly the same speed, stepping, etc., as the previous cpu. This significantly reduces the time to boot very large systems.
Index: linux/arch/ia64/kernel/smpboot.c
=================================--- linux.orig/arch/ia64/kernel/smpboot.c 2007-03-26 15:04:29.322256475 -0500
+++ linux/arch/ia64/kernel/smpboot.c 2007-03-27 08:26:41.914042190 -0500
@@ -424,7 +424,19 @@ smp_callin (void)
* Get our bogomips.
*/
ia64_init_itm();
- calibrate_delay();
+
+ /*
+ * Delay calibration can be skipped if new processor is identical to the
+ * previous processor.
+ */
+ if (local_cpu_data->itc_freq != per_cpu(cpu_info, cpuid - 1).itc_freq || + local_cpu_data->proc_freq != per_cpu(cpu_info, cpuid - 1).proc_freq || + local_cpu_data->features != per_cpu(cpu_info, cpuid - 1).features || + local_cpu_data->revision != per_cpu(cpu_info, cpuid - 1).revision || + local_cpu_data->family != per_cpu(cpu_info, cpuid - 1).family || + local_cpu_data->archrev != per_cpu(cpu_info, cpuid - 1).archrev || + local_cpu_data->model != per_cpu(cpu_info, cpuid - 1).model)
+ calibrate_delay();
local_cpu_data->loops_per_jiffy = loops_per_jiffy;
#ifdef CONFIG_IA32_SUPPORT
Review
Quoted 8 lines · Jack Steiner
(quoted diff) +8
-0+ if (local_cpu_data->itc_freq != per_cpu(cpu_info, cpuid - 1).itc_freq || + local_cpu_data->proc_freq != per_cpu(cpu_info, cpuid - 1).proc_freq || + local_cpu_data->features != per_cpu(cpu_info, cpuid - 1).features || + local_cpu_data->revision != per_cpu(cpu_info, cpuid - 1).revision || + local_cpu_data->family != per_cpu(cpu_info, cpuid - 1).family || + local_cpu_data->archrev != per_cpu(cpu_info, cpuid - 1).archrev || + local_cpu_data->model != per_cpu(cpu_info, cpuid - 1).model) + calibrate_delay();
If you use a temporary variable, you improve speed a little, and you don't exceed 80 columns:
+ struct cpuinfo_ia64 *last_cpu_info = cpu_data(cpuid - 1);
+ struct cpuinfo_ia64 *this_cpu_info = local_cpu_data;
+ if (last_cpu_info->itc_freq != this_cpu_info->itc_freq ||
+ last_cpu_info->proc_freq != this_cpu_info->proc_freq || + last_cpu_info->features != this_cpu_info->features || + last_cpu_info->revision != this_cpu_info->revision || + last_cpu_info->family != this_cpu_info->family || + last_cpu_info->archrev != this_cpu_info->archrev || + last_cpu_info->model != this_cpu_info->model)
+ calibrate_delay();
Quoted 3 lines
Skip clock calibration if cpu being brought online is exactly the same speed, stepping, etc., as the previous cpu. This significantly reduces the time to boot very large systems.
Do we scan through the cpus in a way that makes this really useful I.e. pounding through the cpus on a node - which are likely to be the same - before going on to the next node? Just looking at the previous cpu won't help as much if we scan "breadth-first".
-Tony
Review
Quoted 2 lines
(quoted diff) +2
-0+ */ + if (local_cpu_data->itc_freq != per_cpu(cpu_info, cpuid -
1).itc_freq >||
Review
Quoted 1 line
(quoted diff) +1
-0+ local_cpu_data->proc_freq != per_cpu(cpu_info,
cpuid - >1).proc_freq ||
BSP (cupid=0) should always calibrate delay. Otherwise the patch won't work.
if (cupid=0)
calibrate_delay()
else
your patch.
Thanks.
-Fenghua
Quoted 8 lines · Fenghua
Review
Quoted 2 lines
(quoted diff) +2
-0+ */ + if (local_cpu_data->itc_freq != per_cpu(cpu_info, cpuid -1).itc_freq >||
Review
Quoted 1 line
(quoted diff) +1
-0+ local_cpu_data->proc_freq != per_cpu(cpu_info,cpuid - >1).proc_freq ||
BSP (cupid=0) should always calibrate delay. Otherwise the patch won't work.
True, but the call to calibrate the delay on cpu 0 comes from a different place. See the call in init/main.c.
The code in smp_callin() is only called for cpus 1, 2, ...
-- jack
Skip clock calibration if cpu being brought online is exactly the same speed, stepping, etc., as the previous cpu. This significantly reduces the time to boot very large systems.
----
Add suggestion from Matthew Wilcox to use local variables to shorten lines.
Index: linux/arch/ia64/kernel/smpboot.c
=================================--- linux.orig/arch/ia64/kernel/smpboot.c 2007-03-27 10:08:13.664475719 -0500
+++ linux/arch/ia64/kernel/smpboot.c 2007-03-27 14:20:44.070836177 -0500
@@ -375,6 +375,7 @@ static void __devinit
smp_callin (void)
{
int cpuid, phys_id, itc_master;
+ struct cpuinfo_ia64 *last_cpuinfo, *this_cpuinfo;
extern void ia64_init_itm(void);
extern volatile int time_keeper_id;
@@ -424,7 +425,21 @@ smp_callin (void)
* Get our bogomips.
*/
ia64_init_itm();
- calibrate_delay();
+
+ /*
+ * Delay calibration can be skipped if new processor is identical to the
+ * previous processor.
+ */
+ last_cpuinfo = cpu_data(cpuid - 1);
+ this_cpuinfo = local_cpu_data;
+ if (last_cpuinfo->itc_freq != this_cpuinfo->itc_freq ||
+ last_cpuinfo->proc_freq != this_cpuinfo->proc_freq || + last_cpuinfo->features != this_cpuinfo->features || + last_cpuinfo->revision != this_cpuinfo->revision || + last_cpuinfo->family != this_cpuinfo->family || + last_cpuinfo->archrev != this_cpuinfo->archrev || + last_cpuinfo->model != this_cpuinfo->model)
+ calibrate_delay();
local_cpu_data->loops_per_jiffy = loops_per_jiffy;
#ifdef CONFIG_IA32_SUPPORT