[v3,2/2] doc: include config options in testpmd user guide

  Update testpmd documentation to include RECORD configuration options,
CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES and
CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS.

Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Phil Yang <phil.yang@arm.com>
---
v3:
 - Replace config/common_base with build/.config (Thomas)

v2:
 - Remove extra '#'.
---
 doc/guides/testpmd_app_ug/build_app.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)
  

On 5/20/2020 4:20 AM, Dharmik Thakkar wrote:
> Update testpmd documentation to include RECORD configuration options,
> CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES and
> CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS.
> 
> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Reviewed-by: Phil Yang <phil.yang@arm.com>
> ---
> v3:
>  - Replace config/common_base with build/.config (Thomas)
> 
> v2:
>  - Remove extra '#'.
> ---
>  doc/guides/testpmd_app_ug/build_app.rst | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/doc/guides/testpmd_app_ug/build_app.rst b/doc/guides/testpmd_app_ug/build_app.rst
> index d1ca9f3d19a9..8c9aaa83187f 100644
> --- a/doc/guides/testpmd_app_ug/build_app.rst
> +++ b/doc/guides/testpmd_app_ug/build_app.rst
> @@ -21,6 +21,18 @@ The basic compilation steps are:
>  
>          export RTE_TARGET=x86_64-native-linux-gcc
>  
> +#.  If required, enable configuration options. For example:
> +
> +    .. code-block:: console
> +
> +        cd to the top-level DPDK directory
> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES\)=n,\1=y,' build/.config
> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS\)=n,\1=y,' build/.config
> +
> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES enables measurement of CPU cycles.
> +
> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS enables display of RX and TX bursts.
> +
>  #.  Build the application:
>  
>      .. code-block:: console
> 

Hi Dharmik,

This patch waiting to address the Thomas comment on document how to enable those
config options in meson. @Thomas, can you please correct if I got it wrong?
  

17/06/2020 20:21, Ferruh Yigit:
> On 5/20/2020 4:20 AM, Dharmik Thakkar wrote:
> > Update testpmd documentation to include RECORD configuration options,
> > CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES and
> > CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS.
> > 
> > Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> > Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > Reviewed-by: Phil Yang <phil.yang@arm.com>
> > ---
> > v3:
> >  - Replace config/common_base with build/.config (Thomas)
> > 
> > v2:
> >  - Remove extra '#'.
> > ---
> >  doc/guides/testpmd_app_ug/build_app.rst | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> > 
> > diff --git a/doc/guides/testpmd_app_ug/build_app.rst b/doc/guides/testpmd_app_ug/build_app.rst
> > index d1ca9f3d19a9..8c9aaa83187f 100644
> > --- a/doc/guides/testpmd_app_ug/build_app.rst
> > +++ b/doc/guides/testpmd_app_ug/build_app.rst
> > @@ -21,6 +21,18 @@ The basic compilation steps are:
> >  
> >          export RTE_TARGET=x86_64-native-linux-gcc
> >  
> > +#.  If required, enable configuration options. For example:
> > +
> > +    .. code-block:: console
> > +
> > +        cd to the top-level DPDK directory
> > +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES\)=n,\1=y,' build/.config
> > +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS\)=n,\1=y,' build/.config
> > +
> > +    Enabling CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES enables measurement of CPU cycles.
> > +
> > +    Enabling CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS enables display of RX and TX bursts.
> > +
> >  #.  Build the application:
> >  
> >      .. code-block:: console
> > 
> 
> Hi Dharmik,
> 
> This patch waiting to address the Thomas comment on document how to enable those
> config options in meson. @Thomas, can you please correct if I got it wrong?

If the doc is only about make, it will be removed in 2 months.
So yes, I think it doesn't make sense to be merged as is.
  

+ Bruce

> On Jun 17, 2020, at 2:48 PM, Thomas Monjalon <thomas@monjalon.net> wrote:
> 
> 17/06/2020 20:21, Ferruh Yigit:
>> On 5/20/2020 4:20 AM, Dharmik Thakkar wrote:
>>> Update testpmd documentation to include RECORD configuration options,
>>> CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES and
>>> CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS.
>>> 
>>> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
>>> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
>>> Reviewed-by: Phil Yang <phil.yang@arm.com>
>>> ---
>>> v3:
>>> - Replace config/common_base with build/.config (Thomas)
>>> 
>>> v2:
>>> - Remove extra '#'.
>>> ---
>>> doc/guides/testpmd_app_ug/build_app.rst | 12 ++++++++++++
>>> 1 file changed, 12 insertions(+)
>>> 
>>> diff --git a/doc/guides/testpmd_app_ug/build_app.rst b/doc/guides/testpmd_app_ug/build_app.rst
>>> index d1ca9f3d19a9..8c9aaa83187f 100644
>>> --- a/doc/guides/testpmd_app_ug/build_app.rst
>>> +++ b/doc/guides/testpmd_app_ug/build_app.rst
>>> @@ -21,6 +21,18 @@ The basic compilation steps are:
>>> 
>>>         export RTE_TARGET=x86_64-native-linux-gcc
>>> 
>>> +#.  If required, enable configuration options. For example:
>>> +
>>> +    .. code-block:: console
>>> +
>>> +        cd to the top-level DPDK directory
>>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES\)=n,\1=y,' build/.config
>>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS\)=n,\1=y,' build/.config
>>> +
>>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES enables measurement of CPU cycles.
>>> +
>>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS enables display of RX and TX bursts.
>>> +
>>> #.  Build the application:
>>> 
>>>     .. code-block:: console
>>> 
>> 
>> Hi Dharmik,
>> 
>> This patch waiting to address the Thomas comment on document how to enable those
>> config options in meson. @Thomas, can you please correct if I got it wrong?
> 
> If the doc is only about make, it will be removed in 2 months.
> So yes, I think it doesn't make sense to be merged as is.
> 

Make sense.

With meson, I see multiple ways to enable configuration options:

1] macro in $(RTE_SDK)/config/rte_config.h
2] using dpdk_conf.set() in $(RTE_SDK)/config/meson.build

I’d appreciate some suggestions on the best way to enable these options.

> 
>
  

19/06/2020 17:38, Dharmik Thakkar:
> + Bruce
> 
> > On Jun 17, 2020, at 2:48 PM, Thomas Monjalon <thomas@monjalon.net> wrote:
> > 
> > 17/06/2020 20:21, Ferruh Yigit:
> >> On 5/20/2020 4:20 AM, Dharmik Thakkar wrote:
> >>> Update testpmd documentation to include RECORD configuration options,
> >>> CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES and
> >>> CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS.
> >>> 
> >>> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> >>> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> >>> Reviewed-by: Phil Yang <phil.yang@arm.com>
> >>> ---
> >>> v3:
> >>> - Replace config/common_base with build/.config (Thomas)
> >>> 
> >>> v2:
> >>> - Remove extra '#'.
> >>> ---
> >>> doc/guides/testpmd_app_ug/build_app.rst | 12 ++++++++++++
> >>> 1 file changed, 12 insertions(+)
> >>> 
> >>> diff --git a/doc/guides/testpmd_app_ug/build_app.rst b/doc/guides/testpmd_app_ug/build_app.rst
> >>> index d1ca9f3d19a9..8c9aaa83187f 100644
> >>> --- a/doc/guides/testpmd_app_ug/build_app.rst
> >>> +++ b/doc/guides/testpmd_app_ug/build_app.rst
> >>> @@ -21,6 +21,18 @@ The basic compilation steps are:
> >>> 
> >>>         export RTE_TARGET=x86_64-native-linux-gcc
> >>> 
> >>> +#.  If required, enable configuration options. For example:
> >>> +
> >>> +    .. code-block:: console
> >>> +
> >>> +        cd to the top-level DPDK directory
> >>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES\)=n,\1=y,' build/.config
> >>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS\)=n,\1=y,' build/.config
> >>> +
> >>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES enables measurement of CPU cycles.
> >>> +
> >>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS enables display of RX and TX bursts.
> >>> +
> >>> #.  Build the application:
> >>> 
> >>>     .. code-block:: console
> >>> 
> >> 
> >> Hi Dharmik,
> >> 
> >> This patch waiting to address the Thomas comment on document how to enable those
> >> config options in meson. @Thomas, can you please correct if I got it wrong?
> > 
> > If the doc is only about make, it will be removed in 2 months.
> > So yes, I think it doesn't make sense to be merged as is.
> > 
> 
> Make sense.
> 
> With meson, I see multiple ways to enable configuration options:
> 
> 1] macro in $(RTE_SDK)/config/rte_config.h
> 2] using dpdk_conf.set() in $(RTE_SDK)/config/meson.build
> 
> I’d appreciate some suggestions on the best way to enable these options.

Neither 1 nor 2 because both are source files.
Configuration must be done in the build directory.

We use "meson -D" to configure options listed in meson_options.txt
The real question is which option we accept to be added.
  

> On Jun 19, 2020, at 10:43 AM, Thomas Monjalon <thomas@monjalon.net> wrote:
> 
> 19/06/2020 17:38, Dharmik Thakkar:
>> + Bruce
>> 
>>> On Jun 17, 2020, at 2:48 PM, Thomas Monjalon <thomas@monjalon.net> wrote:
>>> 
>>> 17/06/2020 20:21, Ferruh Yigit:
>>>> On 5/20/2020 4:20 AM, Dharmik Thakkar wrote:
>>>>> Update testpmd documentation to include RECORD configuration options,
>>>>> CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES and
>>>>> CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS.
>>>>> 
>>>>> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
>>>>> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
>>>>> Reviewed-by: Phil Yang <phil.yang@arm.com>
>>>>> ---
>>>>> v3:
>>>>> - Replace config/common_base with build/.config (Thomas)
>>>>> 
>>>>> v2:
>>>>> - Remove extra '#'.
>>>>> ---
>>>>> doc/guides/testpmd_app_ug/build_app.rst | 12 ++++++++++++
>>>>> 1 file changed, 12 insertions(+)
>>>>> 
>>>>> diff --git a/doc/guides/testpmd_app_ug/build_app.rst b/doc/guides/testpmd_app_ug/build_app.rst
>>>>> index d1ca9f3d19a9..8c9aaa83187f 100644
>>>>> --- a/doc/guides/testpmd_app_ug/build_app.rst
>>>>> +++ b/doc/guides/testpmd_app_ug/build_app.rst
>>>>> @@ -21,6 +21,18 @@ The basic compilation steps are:
>>>>> 
>>>>>        export RTE_TARGET=x86_64-native-linux-gcc
>>>>> 
>>>>> +#.  If required, enable configuration options. For example:
>>>>> +
>>>>> +    .. code-block:: console
>>>>> +
>>>>> +        cd to the top-level DPDK directory
>>>>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES\)=n,\1=y,' build/.config
>>>>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS\)=n,\1=y,' build/.config
>>>>> +
>>>>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES enables measurement of CPU cycles.
>>>>> +
>>>>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS enables display of RX and TX bursts.
>>>>> +
>>>>> #.  Build the application:
>>>>> 
>>>>>    .. code-block:: console
>>>>> 
>>>> 
>>>> Hi Dharmik,
>>>> 
>>>> This patch waiting to address the Thomas comment on document how to enable those
>>>> config options in meson. @Thomas, can you please correct if I got it wrong?
>>> 
>>> If the doc is only about make, it will be removed in 2 months.
>>> So yes, I think it doesn't make sense to be merged as is.
>>> 
>> 
>> Make sense.
>> 
>> With meson, I see multiple ways to enable configuration options:
>> 
>> 1] macro in $(RTE_SDK)/config/rte_config.h
>> 2] using dpdk_conf.set() in $(RTE_SDK)/config/meson.build
>> 
>> I’d appreciate some suggestions on the best way to enable these options.
> 
> Neither 1 nor 2 because both are source files.
> Configuration must be done in the build directory.
> 
> We use "meson -D" to configure options listed in meson_options.txt
> The real question is which option we accept to be added.
> 
> 

Yes, correct. There are suggestions for making these as runtime configuration functions which can be enabled(or disabled) using ’set’ from within the application.
Do you think, till this change is implemented, these options can be included in meson_options.txt?

>
  

19/06/2020 18:13, Dharmik Thakkar:
> > On Jun 19, 2020, at 10:43 AM, Thomas Monjalon <thomas@monjalon.net> wrote:
> > 19/06/2020 17:38, Dharmik Thakkar:
> >>> On Jun 17, 2020, at 2:48 PM, Thomas Monjalon <thomas@monjalon.net> wrote:
> >>> 17/06/2020 20:21, Ferruh Yigit:
> >>>> On 5/20/2020 4:20 AM, Dharmik Thakkar wrote:
> >>>>> Update testpmd documentation to include RECORD configuration options,
> >>>>> CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES and
> >>>>> CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS.
> >>>>> 
> >>>>> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> >>>>> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> >>>>> Reviewed-by: Phil Yang <phil.yang@arm.com>
> >>>>> ---
> >>>>> v3:
> >>>>> - Replace config/common_base with build/.config (Thomas)
> >>>>> 
> >>>>> v2:
> >>>>> - Remove extra '#'.
> >>>>> ---
> >>>>> doc/guides/testpmd_app_ug/build_app.rst | 12 ++++++++++++
> >>>>> 1 file changed, 12 insertions(+)
> >>>>> 
> >>>>> diff --git a/doc/guides/testpmd_app_ug/build_app.rst b/doc/guides/testpmd_app_ug/build_app.rst
> >>>>> index d1ca9f3d19a9..8c9aaa83187f 100644
> >>>>> --- a/doc/guides/testpmd_app_ug/build_app.rst
> >>>>> +++ b/doc/guides/testpmd_app_ug/build_app.rst
> >>>>> @@ -21,6 +21,18 @@ The basic compilation steps are:
> >>>>> 
> >>>>>        export RTE_TARGET=x86_64-native-linux-gcc
> >>>>> 
> >>>>> +#.  If required, enable configuration options. For example:
> >>>>> +
> >>>>> +    .. code-block:: console
> >>>>> +
> >>>>> +        cd to the top-level DPDK directory
> >>>>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES\)=n,\1=y,' build/.config
> >>>>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS\)=n,\1=y,' build/.config
> >>>>> +
> >>>>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES enables measurement of CPU cycles.
> >>>>> +
> >>>>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS enables display of RX and TX bursts.
> >>>>> +
> >>>>> #.  Build the application:
> >>>>> 
> >>>>>    .. code-block:: console
> >>>>> 
> >>>> 
> >>>> Hi Dharmik,
> >>>> 
> >>>> This patch waiting to address the Thomas comment on document how to enable those
> >>>> config options in meson. @Thomas, can you please correct if I got it wrong?
> >>> 
> >>> If the doc is only about make, it will be removed in 2 months.
> >>> So yes, I think it doesn't make sense to be merged as is.
> >>> 
> >> 
> >> Make sense.
> >> 
> >> With meson, I see multiple ways to enable configuration options:
> >> 
> >> 1] macro in $(RTE_SDK)/config/rte_config.h
> >> 2] using dpdk_conf.set() in $(RTE_SDK)/config/meson.build
> >> 
> >> I’d appreciate some suggestions on the best way to enable these options.
> > 
> > Neither 1 nor 2 because both are source files.
> > Configuration must be done in the build directory.
> > 
> > We use "meson -D" to configure options listed in meson_options.txt
> > The real question is which option we accept to be added.
> > 
> > 
> 
> Yes, correct. There are suggestions for making these as runtime configuration functions which can be enabled(or disabled) using ’set’ from within the application.

I don't understand this proposal.
Is there a patch?

> Do you think, till this change is implemented, these options can be included in meson_options.txt?

In general, if you think there is a better alternative,
please propose a patch.

I have no opinion what is best to manage such option.
  

> On Jun 22, 2020, at 10:26 AM, Thomas Monjalon <thomas@monjalon.net> wrote:
> 
> 19/06/2020 18:13, Dharmik Thakkar:
>>> On Jun 19, 2020, at 10:43 AM, Thomas Monjalon <thomas@monjalon.net> wrote:
>>> 19/06/2020 17:38, Dharmik Thakkar:
>>>>> On Jun 17, 2020, at 2:48 PM, Thomas Monjalon <thomas@monjalon.net> wrote:
>>>>> 17/06/2020 20:21, Ferruh Yigit:
>>>>>> On 5/20/2020 4:20 AM, Dharmik Thakkar wrote:
>>>>>>> Update testpmd documentation to include RECORD configuration options,
>>>>>>> CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES and
>>>>>>> CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS.
>>>>>>> 
>>>>>>> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
>>>>>>> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
>>>>>>> Reviewed-by: Phil Yang <phil.yang@arm.com>
>>>>>>> ---
>>>>>>> v3:
>>>>>>> - Replace config/common_base with build/.config (Thomas)
>>>>>>> 
>>>>>>> v2:
>>>>>>> - Remove extra '#'.
>>>>>>> ---
>>>>>>> doc/guides/testpmd_app_ug/build_app.rst | 12 ++++++++++++
>>>>>>> 1 file changed, 12 insertions(+)
>>>>>>> 
>>>>>>> diff --git a/doc/guides/testpmd_app_ug/build_app.rst b/doc/guides/testpmd_app_ug/build_app.rst
>>>>>>> index d1ca9f3d19a9..8c9aaa83187f 100644
>>>>>>> --- a/doc/guides/testpmd_app_ug/build_app.rst
>>>>>>> +++ b/doc/guides/testpmd_app_ug/build_app.rst
>>>>>>> @@ -21,6 +21,18 @@ The basic compilation steps are:
>>>>>>> 
>>>>>>>       export RTE_TARGET=x86_64-native-linux-gcc
>>>>>>> 
>>>>>>> +#.  If required, enable configuration options. For example:
>>>>>>> +
>>>>>>> +    .. code-block:: console
>>>>>>> +
>>>>>>> +        cd to the top-level DPDK directory
>>>>>>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES\)=n,\1=y,' build/.config
>>>>>>> +        sed -i 's,\(CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS\)=n,\1=y,' build/.config
>>>>>>> +
>>>>>>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_CORE_CYCLES enables measurement of CPU cycles.
>>>>>>> +
>>>>>>> +    Enabling CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS enables display of RX and TX bursts.
>>>>>>> +
>>>>>>> #.  Build the application:
>>>>>>> 
>>>>>>>   .. code-block:: console
>>>>>>> 
>>>>>> 
>>>>>> Hi Dharmik,
>>>>>> 
>>>>>> This patch waiting to address the Thomas comment on document how to enable those
>>>>>> config options in meson. @Thomas, can you please correct if I got it wrong?
>>>>> 
>>>>> If the doc is only about make, it will be removed in 2 months.
>>>>> So yes, I think it doesn't make sense to be merged as is.
>>>>> 
>>>> 
>>>> Make sense.
>>>> 
>>>> With meson, I see multiple ways to enable configuration options:
>>>> 
>>>> 1] macro in $(RTE_SDK)/config/rte_config.h
>>>> 2] using dpdk_conf.set() in $(RTE_SDK)/config/meson.build
>>>> 
>>>> I’d appreciate some suggestions on the best way to enable these options.
>>> 
>>> Neither 1 nor 2 because both are source files.
>>> Configuration must be done in the build directory.
>>> 
>>> We use "meson -D" to configure options listed in meson_options.txt
>>> The real question is which option we accept to be added.
>>> 
>>> 
>> 
>> Yes, correct. There are suggestions for making these as runtime configuration functions which can be enabled(or disabled) using ’set’ from within the application.
> 
> I don't understand this proposal.
> Is there a patch?
> 
>> Do you think, till this change is implemented, these options can be included in meson_options.txt?
> 
> In general, if you think there is a better alternative,
> please propose a patch.

I am not sure if changing it to a runtime function is a better alternative.
I am expecting some performance degradation with the change since the macros will be replaced with ‘if’ statements.
I will hack up a patch to see the performance difference and propose if there is not much of a difference.

> 
> I have no opinion what is best to manage such option.