Messages in this thread Patches in this message | | | Date | Fri, 13 Jul 2007 16:45:04 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is underway. |
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On Mon, 9 Jul 2007 11:53:02 -0400 darnok@68k.org wrote:
> static void print_trace_address(void *data, unsigned long addr) > { > + static int i = 0; > + if (i && ((i % 8) == 0)) > + touch_nmi_watchdog(); > + i++; > printk_address(addr); > }
I doubt if the "% 8" thing is really needed? printk_address() is pretty slow and touch_nmi_watchdog is _reasonably_ fast. It could be made heaps faster by:
From: Andrew Morton <akpm@linux-foundation.org>
Avoid dirtying remote cpu's memory if it already has the correct value.
Cc: Andi Kleen <ak@suse.de> Cc: Konrad Rzeszutek <konrad@darnok.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
arch/i386/kernel/nmi.c | 8 +++++--- x86_64/kernel/nmi.c | 0 2 files changed, 5 insertions(+), 3 deletions(-)
diff -puN arch/i386/kernel/nmi.c~i386-speedup-touch_nmi_watchdog arch/i386/kernel/nmi.c --- a/arch/i386/kernel/nmi.c~i386-speedup-touch_nmi_watchdog +++ a/arch/i386/kernel/nmi.c @@ -298,7 +298,7 @@ static unsigned int last_irq_sums [NR_CPUS], alert_counter [NR_CPUS]; -void touch_nmi_watchdog (void) +void touch_nmi_watchdog(void) { if (nmi_watchdog > 0) { unsigned cpu; @@ -307,8 +307,10 @@ void touch_nmi_watchdog (void) * Just reset the alert counters, (other CPUs might be * spinning on locks we hold): */ - for_each_present_cpu (cpu) - alert_counter[cpu] = 0; + for_each_present_cpu(cpu) { + if (alert_counter[cpu]) + alert_counter[cpu] = 0; + } } /* So I'd be inclined to simplify your patch to a bare
From: Konrad Rzeszutek <konrad@darnok.org>
On large memory configuration with not so fast CPUs the NMI watchdog is triggered when memory addresses are being gathered and printed. The code paths for Alt-SysRq-t are sprinkled with touch_nmi_watchdog in various places but not in this routine (or in the loop that utilizes this function). The patch has been tested for regression on large CPU+memory configuration (128 logical CPUs + 224 GB) and 1,2,4,16-CPU sockets with various memory sizes (1,2,4,6,20).
Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- arch/x86_64/kernel/traps.c | 1 + 1 files changed, 1 insertion(+) diff -puN arch/x86_64/kernel/traps.c~inhibit-nmi-watchdog-when-alt-sysrq-t-operation-is-underway arch/x86_64/kernel/traps.c --- a/arch/x86_64/kernel/traps.c~inhibit-nmi-watchdog-when-alt-sysrq-t-operation-is-underway +++ a/arch/x86_64/kernel/traps.c @@ -397,6 +397,7 @@ static int print_trace_stack(void *data, static void print_trace_address(void *data, unsigned long addr) { + touch_nmi_watchdog(); printk_address(addr); } _
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