* [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is underway.
@ 2007-07-09 14:02 Konrad Rzeszutek
2007-07-09 15:53 ` darnok
0 siblings, 1 reply; 5+ messages in thread
From: Konrad Rzeszutek @ 2007-07-09 14:02 UTC (permalink / raw)
To: linux-kernel
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).
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is underway.
2007-07-09 14:02 [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is underway Konrad Rzeszutek
@ 2007-07-09 15:53 ` darnok
2007-07-13 23:45 ` Andrew Morton
0 siblings, 1 reply; 5+ messages in thread
From: darnok @ 2007-07-09 15:53 UTC (permalink / raw)
To: linux-kernel
On Mon, Jul 09, 2007 at 10:02:42AM -0400, Konrad Rzeszutek wrote:
> 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).
And the patch:
diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index aac1c0b..b6e7d67 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -330,6 +330,10 @@ static int print_trace_stack(void *data,
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);
}
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is underway.
2007-07-09 15:53 ` darnok
@ 2007-07-13 23:45 ` Andrew Morton
2007-07-20 11:18 ` Konrad Rzeszutek
0 siblings, 1 reply; 5+ messages in thread
From: Andrew Morton @ 2007-07-13 23:45 UTC (permalink / raw)
To: darnok; +Cc: linux-kernel
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);
}
_
OK?
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is underway.
2007-07-13 23:45 ` Andrew Morton
@ 2007-07-20 11:18 ` Konrad Rzeszutek
2007-07-20 21:06 ` Andrew Morton
0 siblings, 1 reply; 5+ messages in thread
From: Konrad Rzeszutek @ 2007-07-20 11:18 UTC (permalink / raw)
To: Andrew Morton; +Cc: darnok, linux-kernel
Hey Andrew,
I tested your patch along with mine and found two things out:
1). Missing this patch (for i386 platform)
diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 90da057..9f3a7ff 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -207,6 +207,7 @@ static void print_trace_address(void *da
{
printk("%s [<%08lx>] ", (char *)data, addr);
print_symbol("%s\n", addr);
+ touch_nmi_watchdog();
}
static struct stacktrace_ops print_trace_ops = {
2). If I run Alt-SysRq-t about 5000 times in a loop, the slow down
with this change is about 5%. Is this a big issue? (This was
testing both i686 and x86_64).
On Fri, Jul 13, 2007 at 04:45:04PM -0700, Andrew Morton wrote:
> 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);
> }
>
> _
>
>
> OK?
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is underway.
2007-07-20 11:18 ` Konrad Rzeszutek
@ 2007-07-20 21:06 ` Andrew Morton
0 siblings, 0 replies; 5+ messages in thread
From: Andrew Morton @ 2007-07-20 21:06 UTC (permalink / raw)
To: Konrad Rzeszutek; +Cc: darnok, linux-kernel
On Fri, 20 Jul 2007 07:18:23 -0400
Konrad Rzeszutek <konrad@darnok.org> wrote:
> I tested your patch along with mine and found two things out:
>
> 1). Missing this patch (for i386 platform)
>
> diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
> index 90da057..9f3a7ff 100644
> --- a/arch/i386/kernel/traps.c
> +++ b/arch/i386/kernel/traps.c
> @@ -207,6 +207,7 @@ static void print_trace_address(void *da
> {
> printk("%s [<%08lx>] ", (char *)data, addr);
> print_symbol("%s\n", addr);
> + touch_nmi_watchdog();
> }
ok...
> static struct stacktrace_ops print_trace_ops = {
>
>
> 2). If I run Alt-SysRq-t about 5000 times in a loop, the slow down
> with this change is about 5%. Is this a big issue? (This was
> testing both i686 and x86_64).
>
I'm surprised. I assume this was when it was printing to a high-speed
device? console or netconsole?
I don't think we need to spend too much time optimising sysrq-T performance ;)
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2007-07-20 21:06 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-07-09 14:02 [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is underway Konrad Rzeszutek
2007-07-09 15:53 ` darnok
2007-07-13 23:45 ` Andrew Morton
2007-07-20 11:18 ` Konrad Rzeszutek
2007-07-20 21:06 ` Andrew Morton
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).