diff options
authorJohn Hawkes <hawkes@sgi.com>2005-05-27 12:53:00 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-05-28 11:14:00 -0700
commitb60c1f6ffd88850079ae419aa933ab0eddbd5535 (patch)
parent[PATCH] arch/i386/kernel/cpu/intel_cacheinfo.c: section fix (diff)
[PATCH] drop note_interrupt() for per-CPU for proper scaling
The "unhandled interrupts" catcher, note_interrupt(), increments a global desc->irq_count and grossly damages scaling of very large systems, e.g., >192p ia64 Altix, because of this highly contented cacheline, especially for timer interrupts. 384p is severely crippled, and 512p is unuseable. All calls to note_interrupt() can be disabled by booting with "noirqdebug", but this disables the useful interrupt checking for all interrupts. I propose eliminating note_interrupt() for all per-CPU interrupts. This was the behavior of linux-2.6.10 and earlier, but in 2.6.11 a code restructuring added a call to note_interrupt() for per-CPU interrupts. Besides, note_interrupt() is a bit racy for concurrent CPU calls anyway, as the desc->irq_count++ increment isn't atomic (which, if done, would make scaling even worse). Signed-off-by: John Hawkes <hawkes@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to '')
1 files changed, 0 insertions, 2 deletions
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 06b5a6323998..436c7d93c00a 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -119,8 +119,6 @@ fastcall unsigned int __do_IRQ(unsigned int irq, struct pt_regs *regs)
action_ret = handle_IRQ_event(irq, regs, desc->action);
- if (!noirqdebug)
- note_interrupt(irq, desc, action_ret);
return 1;