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| author | H. Peter Anvin <hpa@zytor.com> | 2010-01-05 06:14:41 +0100 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2010-01-05 06:28:24 +0100 |
| commit | ea94396629a3e0cb9a3a9c75335b1de255b30426 (patch) | |
| tree | 32208d082a54a3069170195c1d046e95620ebd8f /arch | |
| parent | x86, apic: Reclaim IDT vectors 0x20-0x2f (diff) | |
| download | linux-ea94396629a3e0cb9a3a9c75335b1de255b30426.tar.xz linux-ea94396629a3e0cb9a3a9c75335b1de255b30426.zip | |
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')
| -rw-r--r-- | arch/x86/include/asm/irq_vectors.h | 9 | ||||
| -rw-r--r-- | arch/x86/kernel/apic/io_apic.c | 3 |
2 files changed, 7 insertions, 5 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 diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index d9cd1f1b9c07..e9ba0903e9d5 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -1162,7 +1162,8 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask) * Also, we've got to be careful not to trash gate * 0x80, because int 0x80 is hm, kind of importantish. ;) */ - static int current_vector = FIRST_DEVICE_VECTOR, current_offset = 0; + static int current_vector = FIRST_DEVICE_VECTOR + VECTOR_OFFSET_START; + static int current_offset = VECTOR_OFFSET_START % 8; unsigned int old_vector; int cpu, err; cpumask_var_t tmp_mask; |