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authorH. Peter Anvin <hpa@zytor.com>2010-01-05 08:14:41 +0300
committerH. Peter Anvin <hpa@zytor.com>2010-01-05 08:28:24 +0300
commitea94396629a3e0cb9a3a9c75335b1de255b30426 (patch)
tree32208d082a54a3069170195c1d046e95620ebd8f /arch/x86/include/asm/irq_vectors.h
parent99d113b17e8ca5a8b68a9d3f7691e2f552dd6a06 (diff)
downloadlinux-ea94396629a3e0cb9a3a9c75335b1de255b30426.tar.xz
x86, apic: Don't waste a vector to improve vector spread
We want to use a vector-assignment sequence that avoids stumbling onto 0x80 earlier in the sequence, in order to improve the spread of vectors across priority levels on machines with a small number of interrupt sources. Right now, this is done by simply making the first vector (0x31 or 0x41) completely unusable. This is unnecessary; all we need is to start assignment at a +1 offset, we don't actually need to prohibit the usage of this vector once we have wrapped around. Signed-off-by: H. Peter Anvin <hpa@zytor.com> LKML-Reference: <4B426550.6000209@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/irq_vectors.h')
-rw-r--r--arch/x86/include/asm/irq_vectors.h9
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index dbc81acb7e93..585a42810cf8 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -133,11 +133,12 @@
#define MCE_SELF_VECTOR 0xeb
/*
- * First APIC vector available to drivers: (vectors 0x30-0xee) we
- * start at 0x31 to spread out vectors evenly between priority
- * levels. (0x80 is the syscall vector)
+ * First APIC vector available to drivers: (vectors 0x30-0xee). We
+ * start allocating at 0x31 to spread out vectors evenly between
+ * priority levels. (0x80 is the syscall vector)
*/
-#define FIRST_DEVICE_VECTOR (IRQ15_VECTOR + 2)
+#define FIRST_DEVICE_VECTOR (IRQ15_VECTOR + 1)
+#define VECTOR_OFFSET_START 1
#define NR_VECTORS 256