[RFC 2/2] Make x86 calibrate_delay run in parallel.

From: Holt <holt
Date: Tue Dec 14 2010 - 20:59:04 EST

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On a 4096 cpu machine, we noticed that 318 seconds were taken for bringing
up the cpus. By specifying lpj=<value>, we reduced that to 75 seconds.
Andi Kleen suggested we rework the calibrate_delay calls to run in
parallel. With that code in place, a test boot of the same machine took
61 seconds to bring the cups up. I am not sure how we beat the lpj=
case, but it did outperform.

One thing to note is the total BogoMIPS value is also consistently higher.
I am wondering if this is an effect with the cores being in performance
mode. I did notice that the parallel calibrate_delay calls did cause the
fans on the machine to ramp up to full speed where the normal sequential
calls did not cause them to budge at all.

Signed-off-by: Robin Holt <holt@xxxxxxx>
To: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>

---

Some before and after logs:

2 socket, 8 cores per socket, no hyperthreads:
Before:
[ 0.816215] Booting Node 0, Processors #1 #2 #3 #4 #5 #6 #7 Ok.
[ 1.463913] Booting Node 1, Processors #8 #9 #10 #11 #12 #13 #14 #15 Ok.
[ 2.202919] Brought up 16 CPUs
[ 2.206325] Total of 16 processors activated (72523.23 BogoMIPS).
# grep bogomips /proc/cpuinfo
bogomips : 4532.81
bogomips : 4532.65
bogomips : 4532.64
bogomips : 4532.64
bogomips : 4532.65
bogomips : 4532.64
bogomips : 4532.64
bogomips : 4532.64
bogomips : 4532.72
bogomips : 4532.74
bogomips : 4532.72
bogomips : 4532.73
bogomips : 4532.74
bogomips : 4532.74
bogomips : 4532.74
bogomips : 4532.73

After:
[ 0.747991] UV: Map MMR_HI 0xf7e00000000 - 0xf7e04000000
[ 0.753913] UV: Map MMIOH_HI 0xf8000000000 - 0xf8100000000
[ 0.760314] Booting Node 0, Processors #1 #2 #3 #4 #5 #6 #7 Ok.
[ 0.990706] Booting Node 1, Processors #8 #9 #10 #11 #12 #13 #14 #15 Ok.
[ 1.253240] Brought up 16 CPUs
[ 1.315378] Total of 16 processors activated (127783.49 BogoMIPS).
# grep bogomips /proc/cpuinfo
bogomips : 4533.49
bogomips : 7890.05
bogomips : 9699.67
bogomips : 10047.13
bogomips : 8276.11
bogomips : 8236.85
bogomips : 10062.50
bogomips : 11421.44
bogomips : 7920.28
bogomips : 7883.65
bogomips : 9700.00
bogomips : 9949.31
bogomips : 6448.05
bogomips : 6443.88
bogomips : 4738.22
bogomips : 4532.79

2 socket, 8 cores per socket, hyperthreaded:
Before:
[ 0.538499] Booting Node 0, Processors #1 #2 #3 #4 #5 #6 #7 Ok.
[ 1.323403] Booting Node 1, Processors #8 #9 #10 #11 #12 #13 #14 #15 Ok.
[ 2.221987] Booting Node 0, Processors #16 #17 #18 #19 #20 #21 #22 #23 Ok.
[ 3.120388] Booting Node 1, Processors #24 #25 #26 #27 #28 #29 #30 #31 Ok.
[ 4.018423] Brought up 32 CPUs
[ 4.021833] Total of 32 processors activated (145083.20 BogoMIPS).
After:
[ 0.771327] Booting Node 0, Processors #1 #2 #3 #4 #5 #6 #7 Ok.
[ 1.001745] Booting Node 1, Processors #8 #9 #10 #11 #12 #13 #14 #15 Ok.
[ 1.264354] Booting Node 0, Processors #16 #17 #18 #19 #20 #21 #22 #23 Ok.
[ 1.528090] Booting Node 1, Processors #24 #25 #26 #27 #28 #29 #30 #31 Ok.
[ 1.790866] Brought up 32 CPUs
[ 1.852380] Total of 32 processors activated (279493.75 BogoMIPS).

2 socket, 6 cores per socket, no hyperthreads:
Before:
[ 0.773336] Booting Node 0, Processors #1 #2 #3 #4 #5 Ok.
[ 1.233990] Booting Node 1, Processors #6 #7 #8 #9 #10 #11 Ok.
[ 1.784768] Brought up 12 CPUs
[ 1.788170] Total of 12 processors activated (63991.86 BogoMIPS).

After:
[ 0.721474] Booting Node 0, Processors #1 #2 #3 #4 #5 Ok.
[ 0.885791] Booting Node 1, Processors #6 #7 #8 #9 #10 #11 Ok.
[ 1.082249] Brought up 12 CPUs
[ 1.144426] Total of 12 processors activated (104214.24 BogoMIPS).

256 socket, 8 cores per socket, hyperthreaded:
Before:
[ 95.105108] Booting Node 0, Processors #1 #2 #3 #4 #5 #6 #7 Ok.
[ 95.768866] Booting Node 1, Processors #8 #9 #10 #11 #12 #13 #14 #15 Ok.
...
[ 410.597682] Booting Node 254, Processors #4080 #4081 #4082 #4083 #4084 #4085 #4086 #4087 Ok.
[ 411.231708] Booting Node 255, Processors #4088 #4089 #4090 #4091 #4092 #4093 #4094 #4095 Ok.
[ 411.859404] Brought up 4096 CPUs
[ 411.861354] Total of 4096 processors activated (18569762.97 BogoMIPS).

After:
[ 68.491186] Booting Node 0, Processors #1 #2 #3 #4 #5 #6 #7 Ok.
[ 68.724012] Booting Node 1, Processors #8 #9 #10 #11 #12 #13 #14 #15 Ok.
...
[ 127.713750] Booting Node 254, Processors #4080 #4081 #4082 #4083 #4084 #4085 #4086 #4087 Ok.
[ 127.842004] Booting Node 255, Processors #4088 #4089 #4090 #4091 #4092 #4093 #4094 #4095 Ok.
[ 127.969171] Brought up 4096 CPUs
[ 128.030130] Total of 4096 processors activated (19160610.04 BogoMIPS).

arch/x86/include/asm/cpumask.h | 1
arch/x86/kernel/cpu/common.c | 2 +
arch/x86/kernel/smpboot.c | 33 ++++++++++++++++++++++---------
3 files changed, 27 insertions(+), 9 deletions(-)

Index: parallelize_calibrate_delay/arch/x86/include/asm/cpumask.h
===================================================================
--- parallelize_calibrate_delay.orig/arch/x86/include/asm/cpumask.h 2010-12-14 18:49:25.414805459 -0600
+++ parallelize_calibrate_delay/arch/x86/include/asm/cpumask.h 2010-12-14 18:50:53.558972740 -0600
@@ -6,6 +6,7 @@
extern cpumask_var_t cpu_callin_mask;
extern cpumask_var_t cpu_callout_mask;
extern cpumask_var_t cpu_initialized_mask;
+extern cpumask_var_t cpu_calibrating_jiffies_mask;
extern cpumask_var_t cpu_sibling_setup_mask;

extern void setup_cpu_local_masks(void);
Index: parallelize_calibrate_delay/arch/x86/kernel/cpu/common.c
===================================================================
--- parallelize_calibrate_delay.orig/arch/x86/kernel/cpu/common.c 2010-12-14 18:49:25.414805459 -0600
+++ parallelize_calibrate_delay/arch/x86/kernel/cpu/common.c 2010-12-14 18:50:53.575016358 -0600
@@ -45,6 +45,7 @@
cpumask_var_t cpu_initialized_mask;
cpumask_var_t cpu_callout_mask;
cpumask_var_t cpu_callin_mask;
+cpumask_var_t cpu_calibrating_jiffies_mask;

/* representing cpus for which sibling maps can be computed */
cpumask_var_t cpu_sibling_setup_mask;
@@ -55,6 +56,7 @@ void __init setup_cpu_local_masks(void)
alloc_bootmem_cpumask_var(&cpu_initialized_mask);
alloc_bootmem_cpumask_var(&cpu_callin_mask);
alloc_bootmem_cpumask_var(&cpu_callout_mask);
+ alloc_bootmem_cpumask_var(&cpu_calibrating_jiffies_mask);
alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);
}

Index: parallelize_calibrate_delay/arch/x86/kernel/smpboot.c
===================================================================
--- parallelize_calibrate_delay.orig/arch/x86/kernel/smpboot.c 2010-12-14 18:50:53.439014660 -0600
+++ parallelize_calibrate_delay/arch/x86/kernel/smpboot.c 2010-12-14 18:50:53.623015192 -0600
@@ -52,6 +52,7 @@
#include <linux/gfp.h>

#include <asm/acpi.h>
+#include <asm/cpumask.h>
#include <asm/desc.h>
#include <asm/nmi.h>
#include <asm/irq.h>
@@ -265,15 +266,7 @@ static void __cpuinit smp_callin(void)
* Need to setup vector mappings before we enable interrupts.
*/
setup_vector_irq(smp_processor_id());
- /*
- * Get our bogomips.
- *
- * Need to enable IRQs because it can take longer and then
- * the NMI watchdog might kill us.
- */
- local_irq_enable();
- loops_per_jiffy = calibrate_delay(loops_per_jiffy);
- local_irq_disable();
+
pr_debug("Stack at about %p\n", &cpuid);

/*
@@ -294,6 +287,8 @@ static void __cpuinit smp_callin(void)
*/
notrace static void __cpuinit start_secondary(void *unused)
{
+ struct cpuinfo_x86 *c;
+
/*
* Don't put *anything* before cpu_init(), SMP booting is too
* fragile that we want to limit the things done here to the
@@ -327,6 +322,12 @@ notrace static void __cpuinit start_seco
wmb();

/*
+ * Indicate we are still calibrating jiffies. Do not sum bogomips
+ * yet.
+ */
+ cpumask_set_cpu(smp_processor_id(), cpu_calibrating_jiffies_mask);
+
+ /*
* We need to hold call_lock, so there is no inconsistency
* between the time smp_call_function() determines number of
* IPI recipients, and the time when the determination is made
@@ -349,6 +350,15 @@ notrace static void __cpuinit start_seco
/* enable local interrupts */
local_irq_enable();

+ c = &cpu_data(smp_processor_id());
+ /*
+ * Get our bogomips.
+ */
+ local_irq_enable();
+ c->loops_per_jiffy = calibrate_delay(loops_per_jiffy);
+ cpumask_clear_cpu(smp_processor_id(), cpu_calibrating_jiffies_mask);
+ smp_mb__after_clear_bit();
+
/* to prevent fake stack check failure in clock setup */
boot_init_stack_canary();

@@ -1190,6 +1200,11 @@ void __init native_smp_prepare_boot_cpu(

void __init native_smp_cpus_done(unsigned int max_cpus)
{
+ while (cpumask_weight(cpu_calibrating_jiffies_mask)) {
+ cpu_relax();
+ touch_nmi_watchdog();
+ }
+
pr_debug("Boot done.\n");

impress_friends();

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Next message: Holt <holt: "[RFC 0/2] Speed large x86_64 system boot by calling calibrate_delay() in parallel."
Previous message: Holt <holt: "[RFC 1/2] Pass loops_per_jiffy in and out of calibrate_delay()."
In reply to: Holt <holt: "[RFC 1/2] Pass loops_per_jiffy in and out of calibrate_delay()."
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]