Re: [PATCH v2] eal/linux: enable the hugepage mem dump

[Li Feng <fengli@smartx.com>]

On Wed, Apr 6, 2022 at 6:46 AM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> On Fri,  1 Apr 2022 17:10:04 +0800
> Li Feng <fengli@smartx.com> wrote:
>
> > These hugepages include important structures. we should dump these
> > hugepages into a coredump file for debugging when generating a coredump.
> >
> > Signed-off-by: Li Feng <fengli@smartx.com>
> > ---
> >  lib/eal/linux/eal_memalloc.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/lib/eal/linux/eal_memalloc.c b/lib/eal/linux/eal_memalloc.c
> > index f8b1588cae..93c4f396cf 100644
> > --- a/lib/eal/linux/eal_memalloc.c
> > +++ b/lib/eal/linux/eal_memalloc.c
> > @@ -677,6 +677,8 @@ alloc_seg(struct rte_memseg *ms, void *addr, int socket_id,
> >                               __func__);
> >  #endif
> >
> > +     eal_mem_set_dump(addr, alloc_sz, true);
> > +
> >       huge_recover_sigbus();
> >
> >       ms->addr = addr;
>
>
> Don't merge this patch as is please; it would cause a lot of pain
> in a cloud environment.
>
> In our environment core dumps are collected (via systemd) and uploaded
> to a central server. With this kind of change the processing would get
> overloaded with multi-gigabyte core dump size. Probably couldn't even
> save a core dump on these kind of smart nics.
>
>
> This needs to be optional (from command line) and default to the current
> behavior (not dumping huge pages).

On Linux, just with this patch, the coredump will not include these
hugepages which are shared,
we should write 0x73 to /proc/self/coredump_filter.
This is the coredump_filter explanation:
       Since  kernel 2.6.23, the Linux-specific
/proc/[pid]/coredump_filter file can be used to control which memory
segments are written to the core dump
       file in the event that a core dump is performed for the process
with the corresponding process ID.

       The value in the file is a bit mask of memory mapping types
(see mmap(2)).  If a bit is set in the mask, then memory mappings of
the  corresponding
       type are dumped; otherwise they are not dumped.  The bits in
this file have the following meanings:

           bit 0  Dump anonymous private mappings.
           bit 1  Dump anonymous shared mappings.
           bit 2  Dump file-backed private mappings.
           bit 3  Dump file-backed shared mappings.
           bit 4 (since Linux 2.6.24)
                  Dump ELF headers.
           bit 5 (since Linux 2.6.28)
                  Dump private huge pages.
           bit 6 (since Linux 2.6.28)
                  Dump shared huge pages.
           bit 7 (since Linux 4.4)
                  Dump private DAX pages.
           bit 8 (since Linux 4.4)
                  Dump shared DAX pages.

       By  default, the following bits are set: 0, 1, 4 (if the
CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS kernel configuration option is
enabled), and 5.  This
       default can be modified at boot time using the coredump_filter
boot option.