linux/kernel/irq
John Hawkes b60c1f6ffd [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>
2005-05-28 11:14:00 -07:00
..
autoprobe.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
handle.c [PATCH] drop note_interrupt() for per-CPU for proper scaling 2005-05-28 11:14:00 -07:00
internals.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
Makefile Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
manage.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
proc.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
spurious.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00