Re: [dpdk-dev] [PATCH v4 1/1] fbarray: get fbarrays from containerized secondary

[David Marchand <david.marchand@redhat.com>]

Some comments.

The title does not reflect the observed issue.
I understand that secondary processeses can't be started from a docker
container.
The patch title should reflect this.

On Wed, Jul 24, 2019 at 10:20 AM <yasufum.o@gmail.com> wrote:
>
> From: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
>
> In secondary_msl_create_walk(), it creates a file for fbarrays with its
> PID for reserving unique name among secondary processes. However, it
> does not work if secondary is run as app container because each of
> containerized secondary has PID 1. To reserve unique name, use hostname
> instead of PID because hostname is assigned as a short form of 64
> digits full container ID in docker.
>
> Cc: stable@dpdk.org

I don't think we want to backport this behavior change.

>
> Signed-off-by: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
> ---
>  lib/librte_eal/linux/eal/eal_memalloc.c | 28 +++++++++++++++++++++++--
>  1 file changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_eal/linux/eal/eal_memalloc.c b/lib/librte_eal/linux/eal/eal_memalloc.c
> index 1f6a7c18f..356b304a8 100644
> --- a/lib/librte_eal/linux/eal/eal_memalloc.c
> +++ b/lib/librte_eal/linux/eal/eal_memalloc.c
> @@ -1366,6 +1366,7 @@ secondary_msl_create_walk(const struct rte_memseg_list *msl,
>         struct rte_memseg_list *primary_msl, *local_msl;
>         char name[PATH_MAX];
>         int msl_idx, ret;
> +       char proc_id[33] = { 0 };  /* 32bytes is enough if using hostname */

This variable only makes sense in the if (getpid() == 1) branch,
please move it there, and see below comment about using gethostname().

>
>         if (msl->external)
>                 return 0;
> @@ -1375,8 +1376,31 @@ secondary_msl_create_walk(const struct rte_memseg_list *msl,
>         local_msl = &local_memsegs[msl_idx];
>
>         /* create distinct fbarrays for each secondary */
> -       snprintf(name, RTE_FBARRAY_NAME_LEN, "%s_%i",
> -               primary_msl->memseg_arr.name, getpid());
> +       /* If run secondary in a container, the name of fbarray file should
> +        * not be decided with pid because getpid() always returns 1.
> +        * In docker, hostname is assigned as a short form of full container
> +        * ID. So use hostname as unique ID among containers instead.

I understand this is how it works for docker.
Is this the same in other container environments?


> +        */
> +       if (getpid() == 1) {
> +               FILE *hn_fp;
> +               hn_fp = fopen("/etc/hostname", "r");

Why not use gethostname() ?
Plus, this api defines the maximum size of the hostname as HOST_NAME_MAX bytes.

> +               if (hn_fp == NULL) {
> +                       RTE_LOG(ERR, EAL,
> +                               "Cannot open '/etc/hostname' for secondary\n");
> +                       return -1;
> +               }
> +
> +               /* with docker, /etc/hostname just has one entry of hostname */
> +               if (fscanf(hn_fp, "%32s", proc_id) == EOF) {
> +                       fclose(hn_fp);
> +                       return -1;
> +               }
> +               fclose(hn_fp);
> +       } else
> +               sprintf(proc_id, "%d", (int)getpid());
> +
> +       snprintf(name, RTE_FBARRAY_NAME_LEN, "%s_%s",
> +                       primary_msl->memseg_arr.name, proc_id);
>
>         ret = rte_fbarray_init(&local_msl->memseg_arr, name,
>                 primary_msl->memseg_arr.len,
> --
> 2.17.1
>


-- 
David Marchand