[dpdk-dev] [PATCH v4] eal: make hugetlb initialization more robust

[David Marchand]

Hello Jianfeng,

On Thu, May 12, 2016 at 2:44 AM, Jianfeng Tan <jianfeng.tan at intel.com> wrote:
> This patch adds an option, --huge-trybest, to use a recover mechanism to
> the case that there are not so many hugepages (declared in sysfs), which
> can be used. It relys on a mem access to fault-in hugepages, and if fails
> with SIGBUS, recover to previously saved stack environment with
> siglongjmp().
>
> Besides, this solution fixes an issue when hugetlbfs is specified with an
> option of size. Currently DPDK does not respect the quota of a hugetblfs
> mount. It fails to init the EAL because it tries to map the number of free
> hugepages in the system rather than using the number specified in the quota
> for that mount.
>
> It's still an open issue with CONFIG_RTE_EAL_SINGLE_FILE_SEGMENTS. Under
> this case (such as IVSHMEM target), having hugetlbfs mounts with quota will
> fail to remap hugepages as it relies on having mapped all free hugepages
> in the system.

For such a case case, maybe having some warning log message when it
fails would help the user.
+ a known issue in the release notes ?


> diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
> index 5b9132c..8c77010 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
> @@ -417,12 +434,33 @@ map_all_hugepages(struct hugepage_file *hugepg_tbl,
>                         hugepg_tbl[i].final_va = virtaddr;
>                 }
>
> +               if (orig && internal_config.huge_trybest) {
> +                       /* In linux, hugetlb limitations, like cgroup, are
> +                        * enforced at fault time instead of mmap(), even
> +                        * with the option of MAP_POPULATE. Kernel will send
> +                        * a SIGBUS signal. To avoid to be killed, save stack
> +                        * environment here, if SIGBUS happens, we can jump
> +                        * back here.
> +                        */
> +                       if (wrap_sigsetjmp()) {
> +                               RTE_LOG(DEBUG, EAL, "SIGBUS: Cannot mmap more "
> +                                       "hugepages of size %u MB\n",
> +                                       (unsigned)(hugepage_sz / 0x100000));
> +                               munmap(virtaddr, hugepage_sz);
> +                               close(fd);
> +                               unlink(hugepg_tbl[i].filepath);
> +                               return i;
> +                       }
> +                       *(int *)virtaddr = 0;
> +               }
> +
> +
>                 /* set shared flock on the file. */
>                 if (flock(fd, LOCK_SH | LOCK_NB) == -1) {
> -                       RTE_LOG(ERR, EAL, "%s(): Locking file failed:%s \n",
> +                       RTE_LOG(DEBUG, EAL, "%s(): Locking file failed:%s \n",
>                                 __func__, strerror(errno));
>                         close(fd);
> -                       return -1;
> +                       return i;
>                 }
>
>                 close(fd);

Maybe I missed something, but we are writing into some hugepage before
the flock has been called.
Are we sure there is nobody else using this hugepage ?

Especially, can't this cause trouble to a primary process running if
we start the exact same primary process ?


-- 
David Marchand