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Commit 9959c888 authored by Yinghai Lu's avatar Yinghai Lu Committed by Ingo Molnar
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x86: Increase NR_IRQS and nr_irqs 



I have a system with lots of igb and ixgbe, when iov/vf are
enabled for them, we hit the limit of 3064.

when system has 20 pcie installed, and one card has 2
functions, and one function needs 64 msi-x,
 may need 20 * 2 * 64 = 2560 for msi-x

but if iov and vf are enabled
 may need 20 * 2 * 64 * 3 = 7680 for msi-x
assume system with 5 ioapic, nr_irqs_gsi will be 120.

NR_CPUS = 512, and nr_cpu_ids = 128
will have NR_IRQS = 256 + 512 * 64 = 33024
will have nr_irqs = 120 + 8 * 128 + 120 * 64 = 8824

When SPARSE_IRQ is not set, there is no increase with kernel data
size.

when NR_CPUS=128, and SPARSE_IRQ is set:
   text		   data	    bss		   dec		 hex	filename
21837444	4216564	12480736	38534744	24bfe58	vmlinux.before
21837442	4216580	12480736	38534758	24bfe66	vmlinux.after
when NR_CPUS=4096, and SPARSE_IRQ is set
   text		   data	    bss		   dec		 hex	filename
21878619	5610244	13415392	40904255	270263f	vmlinux.before
21878617	5610244	13415392	40904253	270263d	vmlinux.after

Signed-off-by: default avatarYinghai Lu <yinghai@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <4B398ECD.1080506@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 6b7b2849

arch/x86/include/asm/irq_vectors.h

+6 −6
Original line number Diff line number Diff line
@@ -154,21 +154,21 @@ static inline int invalid_vm86_irq(int irq) 


#define NR_IRQS_LEGACY			  16



#define CPU_VECTOR_LIMIT		(  8 * NR_CPUS      )

#define IO_APIC_VECTOR_LIMIT		( 32 * MAX_IO_APICS )



#ifdef CONFIG_X86_IO_APIC

# ifdef CONFIG_SPARSE_IRQ

#  define CPU_VECTOR_LIMIT		(64 * NR_CPUS)

#  define NR_IRQS					\

	(CPU_VECTOR_LIMIT > IO_APIC_VECTOR_LIMIT ?	\

		(NR_VECTORS + CPU_VECTOR_LIMIT)  :	\

		(NR_VECTORS + IO_APIC_VECTOR_LIMIT))

# else

#  if NR_CPUS < MAX_IO_APICS

#   define NR_IRQS 			(NR_VECTORS + 4*CPU_VECTOR_LIMIT)

#  else

#   define NR_IRQS			(NR_VECTORS + IO_APIC_VECTOR_LIMIT)

#  endif

#  define CPU_VECTOR_LIMIT		(32 * NR_CPUS)

#  define NR_IRQS					\

	(CPU_VECTOR_LIMIT < IO_APIC_VECTOR_LIMIT ?	\

		(NR_VECTORS + CPU_VECTOR_LIMIT)  :	\

		(NR_VECTORS + IO_APIC_VECTOR_LIMIT))

# endif

#else /* !CONFIG_X86_IO_APIC: */

# define NR_IRQS			NR_IRQS_LEGACY

arch/x86/kernel/apic/io_apic.c

+1 −1
Original line number Diff line number Diff line
@@ -3840,7 +3840,7 @@ int __init arch_probe_nr_irqs(void) 
	/*

	 * for MSI and HT dyn irq

	 */

	nr += nr_irqs_gsi * 16;

	nr += nr_irqs_gsi * 64;

#endif

	if (nr < nr_irqs)

		nr_irqs = nr;