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From: "Wiles, Keith" <keith.wiles@intel.com>
To: Matan Azrad <matan@mellanox.com>
CC: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>,
"jerin.jacob@caviumnetworks.com" <jerin.jacob@caviumnetworks.com>, "Thomas
Monjalon" <thomas@monjalon.net>, "dev@dpdk.org" <dev@dpdk.org>
Thread-Topic: [dpdk-dev] [PATCH 1/2] eal: add API to align integer to
previous power of 2
Thread-Index: AQHTqH9YhrarJeV/c02BHfwy89nKE6Oq0lgA
Date: Sun, 18 Feb 2018 15:39:09 +0000
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References: <20180217104934.17291-1-pbhagavatula@caviumnetworks.com>
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Subject: Re: [dpdk-dev] [PATCH 1/2] eal: add API to align integer
to previous power of 2
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> On Feb 18, 2018, at 12:11 AM, Matan Azrad <matan@mellanox.com> wrote:
>=20
> Hi Pavan
>=20
> Please see some comments below.
>=20
> From: Pavan Nikhilesh, Saturday, February 17, 2018 12:50 PM
>> Add 32b and 64b API's to align the given integer to the previous power o=
f 2.
>>=20
>> Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
>> ---
>> lib/librte_eal/common/include/rte_common.h | 36
>> ++++++++++++++++++++++++++++++
>> 1 file changed, 36 insertions(+)
>>=20
>> diff --git a/lib/librte_eal/common/include/rte_common.h
>> b/lib/librte_eal/common/include/rte_common.h
>> index c7803e41c..126914f07 100644
>> --- a/lib/librte_eal/common/include/rte_common.h
>> +++ b/lib/librte_eal/common/include/rte_common.h
>> @@ -259,6 +259,24 @@ rte_align32pow2(uint32_t x)
>> return x + 1;
>> }
>>=20
>> +/**
>> + * Aligns input parameter to the previous power of 2
>> + *
>> + * @param x
>> + * The integer value to algin
>> + *
>> + * @return
>> + * Input parameter aligned to the previous power of 2
>=20
> I think the zero case(x=3D0) result should be documented.
>=20
>> + */
>> +static inline uint32_t
>> +rte_align32lowpow2(uint32_t x)
>=20
> What do you think about " rte_align32prevpow2"?
>=20
>> +{
>> + x =3D rte_align32pow2(x);
>=20
> In case of x is power of 2 number(already aligned), looks like the resu=
lt here is x and the final result is (x >> 1)?
> Is it as you expect?
>=20
>> + x--;
>> +
>> + return x - (x >> 1);
>=20
> Why can't the implementation just be:
> return rte_align32pow2(x) >> 1;
>=20
> If the above is correct, Are you sure we need this API?
>=20
>> +}
>> +
>> /**
>> * Aligns 64b input parameter to the next power of 2
>> *
>> @@ -282,6 +300,24 @@ rte_align64pow2(uint64_t v)
>> return v + 1;
>> }
>>=20
>> +/**
>> + * Aligns 64b input parameter to the previous power of 2
>> + *
>> + * @param v
>> + * The 64b value to align
>> + *
>> + * @return
>> + * Input parameter aligned to the previous power of 2
>> + */
>> +static inline uint64_t
>> +rte_align64lowpow2(uint64_t v)
>> +{
>> + v =3D rte_align64pow2(v);
>> + v--;
>> +
>> + return v - (v >> 1);
>> +}
>> +
>=20
> Same comments for 64b API.
>=20
>> /*********** Macros for calculating min and max **********/
>>=20
>> /**
>> --
>> 2.16.1
>=20
>=20
> If it is a new API, I think it should be added to the map file and to be =
tagged as experimental. No?
>=20
Is this the type of API that needs to be marked experimental, we should be =
able to prove these functions, correct?
> Matan
Regards,
Keith