On Mon, 2009-06-15 at 08:40 -0500, Maynard Johnson wrote:
> Looks like this posting got overlooked, so I'm re-posting the original patch.
> Ben, can you please review? BTW, Anton reported the problem that this patch
> fixes.
It was merged upstream after 2.6.30 -rc6, see commit e5fc948b...
Cheers,
Ben.
> Thanks.
> -Maynard
>
> ==============================================================
>
>
> Description
> -----------
> Change ppc64 oprofile kernel driver to use the SLOT bits (MMCRA[37:39]only on
> older processors where those bits are defined.
>
> Background
> ----------
> The performance monitor unit of the 64-bit POWER processor family has the
> ability to collect accurate instruction-level samples when profiling on
> marked
> events (i.e., "PM_MRK_<event-name>"). In processors prior to POWER6, the
> MMCRA
> register contained "slot information" that the oprofile kernel driver used to
> adjust the value latched in the SIAR at the time of a PMU interrupt. But as
> of
> POWER6, these slot bits in MMCRA are no longer necessary for oprofile to use,
> since the SIAR itself holds the accurate sampled instruction address. With
> POWER6, these MMCRA slot bits were zero'ed out by hardware so oprofile's use
> of
> these slot bits was, in effect, a NOP. But with POWER7, these bits are no
> longer zero'ed out; however, they serve some other purpose rather than slot
> information. Thus, using these bits on POWER7 to adjust the SIAR value
> results
> in samples being attributed to the wrong instructions. The attached patch
> changes the oprofile kernel driver to ignore these slot bits on all newer
> processors starting with POWER6.
>
> Thanks.
> -Maynard
>
> Signed-off-by: Maynard Johnson <mayna...@us.ibm.com>
>
>
>
> diff -paur linux/arch/powerpc/oprofile/op_model_power4.c
> linux-p7-oprofile-patch//arch/powerpc/oprofile/op_model_power4.c
> --- linux/arch/powerpc/oprofile/op_model_power4.c 2009-05-01
> 08:20:21.000000000 -0500
> +++ linux-p7-oprofile-patch//arch/powerpc/oprofile/op_model_power4.c
> 2009-05-01 08:20:05.000000000 -0500
> @@ -26,6 +26,7 @@
> static unsigned long reset_value[OP_MAX_COUNTER];
>
> static int oprofile_running;
> +static int use_slot_nums;
>
> /* mmcr values are set in power4_reg_setup, used in power4_cpu_setup */
> static u32 mmcr0_val;
> @@ -61,6 +62,12 @@ static int power4_reg_setup(struct op_co
> else
> mmcr0_val |= MMCR0_PROBLEM_DISABLE;
>
> + if (__is_processor(PV_POWER4) || __is_processor(PV_POWER4p) ||
> + __is_processor(PV_970) || __is_processor(PV_970FX) ||
> + __is_processor(PV_970MP) || __is_processor(PV_970GX) ||
> + __is_processor(PV_POWER5) || __is_processor(PV_POWER5p))
> + use_slot_nums = 1;
> +
> return 0;
> }
>
> @@ -206,7 +213,7 @@ static unsigned long get_pc(struct pt_re
>
> mmcra = mfspr(SPRN_MMCRA);
>
> - if (mmcra & MMCRA_SAMPLE_ENABLE) {
> + if (use_slot_nums && (mmcra & MMCRA_SAMPLE_ENABLE)) {
> slot = ((mmcra & MMCRA_SLOT) >> MMCRA_SLOT_SHIFT);
> if (slot > 1)
> pc += 4 * (slot - 1);
>
>
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