Commit-ID: ea94396629a3e0cb9a3a9c75335b1de255b30426 Gitweb: http://git.kernel.org/tip/ea94396629a3e0cb9a3a9c75335b1de255b30426 Author: H. Peter Anvin <hpa@xxxxxxxxx> AuthorDate: Mon, 4 Jan 2010 21:14:41 -0800 Committer: H. Peter Anvin <hpa@xxxxxxxxx> CommitDate: Mon, 4 Jan 2010 21:28:24 -0800 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@xxxxxxxxx> LKML-Reference: <4B426550.6000209@xxxxxxxxxx> --- arch/x86/include/asm/irq_vectors.h | 9 +++++---- 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 dbc81ac..585a428 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 d9cd1f1..e9ba090 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; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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