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Subject[patch 3/3] x86,apic: limit apic dumping, introduce show_lapic setup option
In case if a system has a large number of cpus printing apics
contents may consume a long time period.

We limit such an output by 1 apic by default. But to have an
ability to see all apics or some part of them we introduce
"show_lapic" setup option which allow us to limit/unlimit
the number of APICs being dumped.

Example: apic=debug show_lapic=5, or apic=debug show_lapic=all

Also move apic_verbosity checking upper that way so helper routines
do not need to inspect it at all.

Suggested-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
arch/x86/kernel/apic/io_apic.c | 47 +++++++++++++++++++++++++++--------------
1 file changed, 32 insertions(+), 15 deletions(-)
Index: linux-2.6.git/arch/x86/kernel/apic/io_apic.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/apic/io_apic.c
+++ linux-2.6.git/arch/x86/kernel/apic/io_apic.c
@@ -1599,9 +1599,6 @@ __apicdebuginit(void) print_IO_APIC(void
struct irq_desc *desc;
unsigned int irq;

- if (apic_verbosity == APIC_QUIET)
- return;
-
printk(KERN_DEBUG "number of MP IRQ sources: %d.\n", mp_irq_entries);
for (i = 0; i < nr_ioapics; i++)
printk(KERN_DEBUG "number of IO-APIC #%d registers: %d.\n",
@@ -1708,9 +1705,6 @@ __apicdebuginit(void) print_APIC_field(i
{
int i;

- if (apic_verbosity == APIC_QUIET)
- return;
-
printk(KERN_DEBUG);

for (i = 0; i < 8; i++)
@@ -1724,9 +1718,6 @@ __apicdebuginit(void) print_local_APIC(v
unsigned int i, v, ver, maxlvt;
u64 icr;

- if (apic_verbosity == APIC_QUIET)
- return;
-
printk(KERN_DEBUG "printing local APIC contents on CPU#%d/%d:\n",
smp_processor_id(), hard_smp_processor_id());
v = apic_read(APIC_ID);
@@ -1824,13 +1815,19 @@ __apicdebuginit(void) print_local_APIC(v
printk("\n");
}

-__apicdebuginit(void) print_all_local_APICs(void)
+__apicdebuginit(void) print_local_APICs(int maxcpu)
{
int cpu;

+ if (!maxcpu)
+ return;
+
preempt_disable();
- for_each_online_cpu(cpu)
+ for_each_online_cpu(cpu) {
+ if (cpu >= maxcpu)
+ break;
smp_call_function_single(cpu, print_local_APIC, NULL, 1);
+ }
preempt_enable();
}

@@ -1839,7 +1836,7 @@ __apicdebuginit(void) print_PIC(void)
unsigned int v;
unsigned long flags;

- if (apic_verbosity == APIC_QUIET || !nr_legacy_irqs)
+ if (!nr_legacy_irqs)
return;

printk(KERN_DEBUG "\nprinting PIC contents\n");
@@ -1866,21 +1863,41 @@ __apicdebuginit(void) print_PIC(void)
printk(KERN_DEBUG "... PIC ELCR: %04x\n", v);
}

-__apicdebuginit(int) print_all_ICs(void)
+static int __initdata show_lapic = 1;
+static __init int setup_show_lapic(char *arg)
+{
+ int num = -1;
+
+ if (strcmp(arg, "all") == 0) {
+ show_lapic = CONFIG_NR_CPUS;
+ } else {
+ get_option(&arg, &num);
+ if (num >= 0)
+ show_lapic = num;
+ }
+
+ return 1;
+}
+__setup("show_lapic=", setup_show_lapic);
+
+__apicdebuginit(int) print_ICs(void)
{
+ if (apic_verbosity == APIC_QUIET)
+ return 0;
+
print_PIC();

/* don't print out if apic is not there */
if (!cpu_has_apic && !apic_from_smp_config())
return 0;

- print_all_local_APICs();
+ print_local_APICs(show_lapic);
print_IO_APIC();

return 0;
}

-fs_initcall(print_all_ICs);
+fs_initcall(print_ICs);


/* Where if anywhere is the i8259 connect in external int mode */


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