watchdog: allow nmi watchdog to use raw perf event

NMI watchdog permanently consumes one hardware counters per CPU on the
system.  For systems that use many hardware counters, this causes more
aggressive time multiplexing of perf events.

OTOH, some CPUs (mostly Intel) support "ref-cycles" event, which is rarely
used.  Add kernel cmdline arg nmi_watchdog=rNNN to configure the watchdog
to use raw event.  For example, on Intel CPUs, we can use "r300" to
configure the watchdog to use ref-cycles event.

If the raw event does not work, fall back to use "cycles".

[[email protected]: fix kerneldoc]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Song Liu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: "Matthew Wilcox (Oracle)" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions