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Date: Sat, 21 Sep 2013 19:58:00 -0000
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Subject: Re: page faults counter example is broken?!
From: "Paddie O'Brien" <paddieobrien@gmail.com>
To: Thomas Knauth <thomas.knauth@googlemail.com>
Cc: systemtap@sourceware.org
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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.