Re: [dpdk-dev] [PATCH v2] eal: use madvise to exclude unmapped memory from being dumped

[Li Feng <fengli@smartx.com>]

Thanks,

Feng Li

Burakov, Anatoly <anatoly.burakov@intel.com> 于2020年4月24日周五 下午7:23写道：
>
> 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@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?
My mistake. I will using v4 for next version.
>
> >
> >   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.

OK. I put this into two places, because the size is more accurate in this place.

>
> >
> >       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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