path: root/arch/ppc/syslib
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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)
treed0f12a263ea1fe3b434de6a5d338509e238d46b3 /arch/ppc/syslib
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>
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