Re: [dpdk-dev] [PATCH] eal: Place EAL thread stack in a reserved per-lcore memzone

[Jerin Jacob <jerinjacobk@gmail.com>]

On Mon, Apr 13, 2020 at 2:39 PM Christos Ricudis <ricudis@niometrics.com> wrote:
>
> Reserve a per-lcore 4MB memzone and allocate thread stack of EAL threads there for better NUMA locality of stack-allocated variables

It looks like a good idea to me.

Some questions/feedback.

1) It is better to get the stack size from OS  through
pthread_attr_getstack() rather than DPDK defining it.
2) There is an element of security issue here as one can get the lcore
stack using rte_memzone_lookup().
Why we need to use memzone, just rte_malloc_socket() is enough here.
Right? This will avoid the security issue.
3) Need to handle EAL --no-huge case as well.



>
> Signed-off-by: Christos Ricudis <ricudis@niometrics.com>
> ---
>  lib/librte_eal/linux/eal.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/lib/librte_eal/linux/eal.c b/lib/librte_eal/linux/eal.c
> index 9530ee5..e047107 100644
> --- a/lib/librte_eal/linux/eal.c
> +++ b/lib/librte_eal/linux/eal.c
> @@ -68,6 +68,8 @@
>
>  #define KERNEL_IOMMU_GROUPS_PATH "/sys/kernel/iommu_groups"
>
> +#define THREAD_STACK_SIZE_DEFAULT (4ULL * 1024ULL * 1024ULL)
> +#include <rte_memzone.h>
>  /* Allow the application to print its usage message too if set */
>  static rte_usage_hook_t        rte_application_usage_hook = NULL;
>
> @@ -1224,6 +1226,24 @@ static void rte_eal_init_alert(const char *msg)
>
>                 lcore_config[i].state = WAIT;
>
> +               pthread_attr_t attr;
> +               pthread_attr_init(&attr);
> +               size_t thread_stack_size = THREAD_STACK_SIZE_DEFAULT;
> +               char thread_stack_name[64];
> +               snprintf(thread_stack_name, sizeof thread_stack_name, "rte:lcore:%s:%d:threadstack", rte_eal_process_type() == RTE_PROC_PRIMARY ? "p" : "s", i);
> +               const struct rte_memzone *mz = rte_memzone_lookup(thread_stack_name);
> +               if (mz == NULL) {
> +                       if ((mz = rte_memzone_reserve(thread_stack_name, thread_stack_size, lcore_config[i].socket_id, 0)) == NULL) {
> +                               rte_panic("Cannot allocate memzone for thread stack");
> +                       }
> +               }
> +               void *thread_stack = mz->addr;
> +
> +               if (pthread_attr_setstack(&attr, thread_stack, thread_stack_size) < 0) {
> +                       rte_panic("Cannot set thread stack\n");
> +               }
> +               RTE_LOG(DEBUG, EAL, "Thread stack for lcore %d on socket %d set to %p\n", i, lcore_config[i].socket_id, thread_stack);
> +
>                 /* create a thread for each lcore */
>                 ret = pthread_create(&lcore_config[i].thread_id, NULL,
>                                      eal_thread_loop, NULL);
> --
> 1.8.3.1
>