* page faults counter example is broken?!
@ 2013-09-20 16:19 Thomas Knauth
0 siblings, 0 replies; 5+ messages in thread
From: Thomas Knauth @ 2013-09-20 16:19 UTC (permalink / raw)
To: systemtap
Dear list,
the system tap examples include a page fault counter. However, I've
noticed that it's way off with the number of page faults it records. A
simple
# stap -c df pfaults.stp
records about 20 page faults (minor and major). A simple cross-check with
# \time df
shows that it should report ~270 page faults.
What am I missing?!
Thanks,
Thomas.
^ permalink raw reply [flat|nested] 5+ messages in thread
* page faults counter example is broken?!
@ 2013-09-20 16:20 Thomas Knauth
2013-09-21 19:58 ` Paddie O'Brien
0 siblings, 1 reply; 5+ messages in thread
From: Thomas Knauth @ 2013-09-20 16:20 UTC (permalink / raw)
To: systemtap
Dear list,
the system tap examples include a page fault counter. However, I've
noticed that it's way off with the number of page faults it records. A
simple
# stap -c df pfaults.stp
records about 20 page faults (minor and major). A simple cross-check with
# \time df
shows that it should report ~270 page faults.
What am I missing?!
Thanks,
Thomas.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: page faults counter example is broken?!
2013-09-20 16:20 Thomas Knauth
@ 2013-09-21 19:58 ` Paddie O'Brien
2013-09-25 15:33 ` Thomas Knauth
0 siblings, 1 reply; 5+ messages in thread
From: Paddie O'Brien @ 2013-09-21 19:58 UTC (permalink / raw)
To: Thomas Knauth; +Cc: systemtap
I think the way minor faults are recorded is the problem. The code below
is used to determine the type of fault (from memory.stp). Perhaps the
check should be:
#if defined(VM_FAULT_MINOR) && VM_FAULT_MINOR == 0
function vm_fault_contains:long (value:long, test:long)
%{
int res;
switch (STAP_ARG_test){
case 0: res = STAP_ARG_value & VM_FAULT_OOM; break;
case 1: res = STAP_ARG_value & VM_FAULT_SIGBUS; break;
#if defined(VM_FAULT_MINOR) && VM_FAULT_MINOR != 0
case 2: /* VM_FAULT_MINOR infered by that flags off */
res = !((VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_MAJOR) &
STAP_ARG_value);
break;
#else
case 2: res = STAP_ARG_value == VM_FAULT_MINOR; break;
On 20 September 2013 17:20, Thomas Knauth <thomas.knauth@googlemail.com> wrote:
> Dear list,
>
> the system tap examples include a page fault counter. However, I've
> noticed that it's way off with the number of page faults it records. A
> simple
>
> # stap -c df pfaults.stp
>
> records about 20 page faults (minor and major). A simple cross-check with
>
> # \time df
>
> shows that it should report ~270 page faults.
>
> What am I missing?!
>
> Thanks,
> Thomas.
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: page faults counter example is broken?!
2013-09-21 19:58 ` Paddie O'Brien
@ 2013-09-25 15:33 ` Thomas Knauth
2013-09-25 15:47 ` Frank Ch. Eigler
0 siblings, 1 reply; 5+ messages in thread
From: Thomas Knauth @ 2013-09-25 15:33 UTC (permalink / raw)
To: Paddie O'Brien; +Cc: systemtap
On Sat, Sep 21, 2013 at 9:58 PM, Paddie O'Brien <paddieobrien@gmail.com> wrote:
> I think the way minor faults are recorded is the problem. The code below
> is used to determine the type of fault (from memory.stp). Perhaps the
> check should be:
>
> #if defined(VM_FAULT_MINOR) && VM_FAULT_MINOR == 0
>
> function vm_fault_contains:long (value:long, test:long)
> %{
> int res;
> switch (STAP_ARG_test){
> case 0: res = STAP_ARG_value & VM_FAULT_OOM; break;
> case 1: res = STAP_ARG_value & VM_FAULT_SIGBUS; break;
> #if defined(VM_FAULT_MINOR) && VM_FAULT_MINOR != 0
> case 2: /* VM_FAULT_MINOR infered by that flags off */
> res = !((VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_MAJOR) &
> STAP_ARG_value);
> break;
> #else
> case 2: res = STAP_ARG_value == VM_FAULT_MINOR; break;
After changing the != into an == operator the number of reported
faults indeed matches with the counters maintained by the OS.
Did this catch the attention of some systemtap developer or shall I
file a separate bug report?
Thanks,
Thomas.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2013-09-25 15:47 UTC | newest]
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2013-09-20 16:19 page faults counter example is broken?! Thomas Knauth
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2013-09-21 19:58 ` Paddie O'Brien
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