[dpdk-dev] [PATCH v3] eal: restrict cores detection

[Jianfeng Tan <jianfeng.tan@intel.com>]

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>
---
v3:
  - Choose a more descriptive variable name, and remove comments
    as suggested by Stephen Hemminger.
v2:
  - Make it as default instead of adding the new options.
 lib/librte_eal/common/eal_common_lcore.c | 9 ++++++++-
 1 file changed, 8 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..71c575c 100644
--- a/lib/librte_eal/common/eal_common_lcore.c
+++ b/lib/librte_eal/common/eal_common_lcore.c
@@ -57,6 +57,12 @@ rte_eal_cpu_init(void)
 	struct rte_config *config = rte_eal_get_configuration();
 	unsigned lcore_id;
 	unsigned count = 0;
+	rte_cpuset_t affinity_set;
+	pthread_t tid = pthread_self();
+
+	if (pthread_getaffinity_np(tid, sizeof(rte_cpuset_t),
+				   &affinity_set) < 0)
+		CPU_ZERO(&affinity_set);
 
 	/*
 	 * Parse the maximum set of logical cores, detect the subset of running
@@ -70,7 +76,8 @@ rte_eal_cpu_init(void)
 
 		/* in 1:1 mapping, record related cpu detected state */
 		lcore_config[lcore_id].detected = eal_cpu_detected(lcore_id);
-		if (lcore_config[lcore_id].detected == 0) {
+		if (lcore_config[lcore_id].detected == 0 ||
+		    !CPU_ISSET(lcore_id, &affinity_set)) {
 			config->lcore_role[lcore_id] = ROLE_OFF;
 			lcore_config[lcore_id].core_index = -1;
 			continue;
-- 
2.7.4