[dpdk-dev] [PATCH v2] eal: use madvise to exclude unmapped memory from being dumped
Burakov, Anatoly
anatoly.burakov at intel.com
Fri Apr 24 13:23:44 CEST 2020
On 24-Apr-20 11:50 AM, Li Feng wrote:
> Currently, even though memory is mapped with PROT_NONE, this does not
> cause it to be excluded from core dumps. This is counter-productive,
> because in a lot of cases, this memory will go unused (e.g. when the
> memory subsystem preallocates VA space but hasn't yet mapped physical
> pages into it).
>
> Use `madvise()` call with MADV_DONTDUMP parameter to exclude the
> unmapped memory from being dumped.
>
> Signed-off-by: Li Feng <fengli at smartx.com>
> ---
> V2:
> - add support for freebsd.
> - when free_seg is called, mark the memory MADV_DONTDUMP.
> - when alloc_seg is called, mark the memory MADV_DODUMP.
Isn't this v3 now?
>
> lib/librte_eal/common/eal_common_memory.c | 26 ++++++++++++++++++++++++++
> lib/librte_eal/linux/eal_memalloc.c | 6 ++++++
> 2 files changed, 32 insertions(+)
>
> diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
> index cc7d54e0c..83be94a20 100644
> --- a/lib/librte_eal/common/eal_common_memory.c
> +++ b/lib/librte_eal/common/eal_common_memory.c
> @@ -177,6 +177,32 @@ eal_get_virtual_area(void *requested_addr, size_t *size,
> after_len = RTE_PTR_DIFF(map_end, aligned_end);
> if (after_len > 0)
> munmap(aligned_end, after_len);
> +
> + /*
> + * Exclude this pages from a core dump.
> + */
> +#ifdef RTE_EXEC_ENV_LINUX
> + if (madvise(aligned_addr, *size, MADV_DONTDUMP) != 0)
> + RTE_LOG(DEBUG, EAL, "madvise failed: %s\n",
> + strerror(errno));
> +#elif RTE_EXEC_ENV_FREEBSD
> + if (madvise(aligned_addr, *size, MADV_NOCORE) != 0)
> + RTE_LOG(DEBUG, EAL, "madvise failed: %s\n",
> + strerror(errno));
> +#endif
> + } else {
> + /*
> + * Exclude this pages from a core dump.
> + */
> +#ifdef RTE_EXEC_ENV_LINUX
> + if (madvise(mapped_addr, map_sz, MADV_DONTDUMP) != 0)
> + RTE_LOG(DEBUG, EAL, "madvise failed: %s\n",
> + strerror(errno));
> +#elif RTE_EXEC_ENV_FREEBSD
> + if (madvise(mapped_addr, map_sz, MADV_NOCORE) != 0)
> + RTE_LOG(DEBUG, EAL, "madvise failed: %s\n",
> + strerror(errno));
> +#endif
> }
DRY (Don't Repeat Yourself) :) Probably easier to do "if (!unmap) ..."
than putting this into two places.
>
> return aligned_addr;
> diff --git a/lib/librte_eal/linux/eal_memalloc.c b/lib/librte_eal/linux/eal_memalloc.c
> index af6d0d023..9d2a6fc6f 100644
> --- a/lib/librte_eal/linux/eal_memalloc.c
> +++ b/lib/librte_eal/linux/eal_memalloc.c
> @@ -571,6 +571,9 @@ alloc_seg(struct rte_memseg *ms, void *addr, int socket_id,
> goto resized;
> }
>
> + if (madvise(addr, alloc_sz, MADV_DODUMP) != 0)
> + RTE_LOG(DEBUG, EAL, "madvise failed: %s\n", strerror(errno));
> +
See discussion for v2, i believe this is unnecessary.
> /* In linux, hugetlb limitations, like cgroup, are
> * enforced at fault time instead of mmap(), even
> * with the option of MAP_POPULATE. Kernel will send
> @@ -687,6 +690,9 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
> return -1;
> }
>
> + if (madvise(ms->addr, ms->len, MADV_DONTDUMP) != 0)
> + RTE_LOG(DEBUG, EAL, "madvise failed: %s\n", strerror(errno));
> +
> exit_early = false;
>
> /* if we're using anonymous hugepages, nothing to be done */
>
--
Thanks,
Anatoly
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