[dpdk-dev] [PATCH v2] eal: restrict cores detection

[Tan, Jianfeng]

Hi Stephen,

> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> Sent: Wednesday, August 31, 2016 11:31 PM
> To: Tan, Jianfeng
> Cc: dev at dpdk.org; david.marchand at 6wind.com; pmatilai at redhat.com;
> thomas.monjalon at 6wind.com
> Subject: Re: [dpdk-dev] [PATCH v2] eal: restrict cores detection
> 
> On Wed, 31 Aug 2016 03:07:10 +0000
> Jianfeng Tan <jianfeng.tan at intel.com> wrote:
> 
> > This patch uses pthread_getaffinity_np() to narrow down detected
> > cores before parsing coremask (-c), corelist (-l), and coremap
> > (--lcores).
> >
> > The purpose of this patch is to leave out these core related options
> > when DPDK applications are deployed under container env, so that
> > users only specify core restriction as starting the instance.
> >
> > Note: previously, some users are using isolated CPUs, which could
> > be excluded by default. Please add commands like taskset to use
> > those cores.
> >
> > Test example:
> > $ taskset 0xc0000 ./examples/helloworld/build/helloworld -m 1024
> >
> > Signed-off-by: Jianfeng Tan <jianfeng.tan at intel.com>
> > Acked-by: Neil Horman <nhorman at tuxdriver.com>
> > ---
> > v2:
> >   - Make it as default instead of adding the new options.
> >  lib/librte_eal/common/eal_common_lcore.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/librte_eal/common/eal_common_lcore.c
> b/lib/librte_eal/common/eal_common_lcore.c
> > index 2cd4132..62e4f67 100644
> > --- a/lib/librte_eal/common/eal_common_lcore.c
> > +++ b/lib/librte_eal/common/eal_common_lcore.c
> > @@ -57,6 +57,14 @@ rte_eal_cpu_init(void)
> >  	struct rte_config *config = rte_eal_get_configuration();
> >  	unsigned lcore_id;
> >  	unsigned count = 0;
> > +	rte_cpuset_t cs;
> > +	pthread_t tid = pthread_self();
> > +
> > +	/* Add below method to obtain core restrictions, like ulimit,
> > +	 * cgroup.cpuset, etc. Will not use those cores, which are rebuffed.
> > +	 */
> > +	if (pthread_getaffinity_np(tid, sizeof(rte_cpuset_t), &cs) < 0)
> > +		CPU_ZERO(&cs);
> >
> 
> This patch makes sense but the comment is hard to read because of wording
> and grammar.
> 
> If you choose variable names better then there really is no need for
> a comment in many cases. Code is often easier to read/write than comments
> for non-native English speakers.
> 
> Remove the comment and rename 'cs' as 'affinity_set' or something equally
> as descriptive.

Great suggestion. I'll resend one as you suggest.

Thanks,
Jianfeng