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From: "Xueming(Steven) Li" <xuemingl@nvidia.com>
To: "ktraynor@redhat.com" <ktraynor@redhat.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Cc: NBU-Contact-Thomas Monjalon <thomas@monjalon.net>,
	"cristian.dumitrescu@intel.com" <cristian.dumitrescu@intel.com>,
	"jasvinder.singh@intel.com" <jasvinder.singh@intel.com>
Subject: Re: [dpdk-dev] [PATCH v1] sched: adds function to get 64 bits greatest common divisor
Date: Thu, 23 Sep 2021 05:34:54 +0000	[thread overview]
Message-ID: <2f4b3c0d88c560322ede5efa10611c1caa40847b.camel@nvidia.com> (raw)
In-Reply-To: <32dc9e20-86dc-a0a6-74a2-9894cb680170@redhat.com>

On Wed, 2021-09-22 at 18:09 +0100, Kevin Traynor wrote:
> On 15/09/2021 11:26, Xueming Li wrote:
> > This patch adds new function that compute the greatest common
> > divisor of 64 bits, also changes the original 32 bits function to call
> > this new 64 bits version.
> > 
> 
> Can you say why it is needed? It's unused apart from being called for 
> the original 32 bit version.

mlx5 vdpa driver is expecting to use a 64 bit version.

> 
> > Signed-off-by: Xueming Li <xuemingl@nvidia.com>
> > ---
> > v1: add 64 bits version and make 32 bits api call it
> > 
> >   lib/sched/rte_sched_common.h | 19 ++++++++++++++++---
> >   1 file changed, 16 insertions(+), 3 deletions(-)
> > 
> > diff --git a/lib/sched/rte_sched_common.h b/lib/sched/rte_sched_common.h
> > index 96706df7bd..1056543a84 100644
> > --- a/lib/sched/rte_sched_common.h
> > +++ b/lib/sched/rte_sched_common.h
> > @@ -51,10 +51,10 @@ rte_min_pos_4_u16(uint16_t *x)
> >    *    gcd(a, b) = gcd(b, a mod b)
> >    *
> >    */
> > -static inline uint32_t
> > -rte_get_gcd(uint32_t a, uint32_t b)
> > +static inline uint64_t
> > +rte_get_gcd64(uint64_t a, uint64_t b)
> >   {
> > -	uint32_t c;
> > +	uint64_t c;
> >   
> >   	if (a == 0)
> >   		return b;
> > @@ -76,6 +76,19 @@ rte_get_gcd(uint32_t a, uint32_t b)
> >   	return a;
> >   }
> >   
> > +/*
> > + * Compute the Greatest Common Divisor (GCD) of two u32 numbers.
> > + * This implementation uses Euclid's algorithm:
> > + *    gcd(a, 0) = a
> > + *    gcd(a, b) = gcd(b, a mod b)
> > + *
> > + */
> 
> I would probably not describe the algorithm here as it is not 
> implemented in this function.

Thanks, I'll just mention that a 32 bit version of GCD.

> 
> > +static inline uint32_t
> > +rte_get_gcd(uint32_t a, uint32_t b)
> > +{
> > +	return rte_get_gcd64(a, b);
> > +}
> > +
> >   /*
> >    * Compute the Lowest Common Denominator (LCD) of two numbers.
> >    * This implementation computes GCD first:
> > 
> 


  reply	other threads:[~2021-09-23  5:34 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-23  8:15 [dpdk-dev] [PATCH] sched: support " Xueming Li
2021-09-15 10:26 ` [dpdk-dev] [PATCH v1] sched: adds function to get " Xueming Li
2021-09-22 17:09   ` Kevin Traynor
2021-09-23  5:34     ` Xueming(Steven) Li [this message]
2021-09-23  8:11     ` [dpdk-dev] [PATCH v2 0/2] " Xueming Li
2021-09-23  8:11       ` [dpdk-dev] [PATCH v2 1/2] " Xueming Li
2021-09-23  9:53         ` Kevin Traynor
2021-09-23  8:11       ` [dpdk-dev] [PATCH v2 2/2] vdpa/mlx5: fix large VM memory region registration Xueming Li
2021-09-27 15:26       ` [dpdk-dev] [PATCH v2 0/2] sched: adds function to get 64 bits greatest common divisor Thomas Monjalon
2021-09-28  5:47         ` Xueming(Steven) Li

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