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

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 31 Aug 2016 03:07:10 +0000
Jianfeng Tan <jianfeng.tan@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@intel.com>
> Acked-by: Neil Horman <nhorman@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.