Re: [dpdk-dev] [PATCH v2] eal: add madvise to avoid dump memory

[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7:00写道：
>
> On 24-Apr-20 10:33 AM, Feng Li wrote:
> > Bruce Richardson <bruce.richardson@intel.com> 于2020年4月24日周五 下午5:14写道：
> >>
> >> On Fri, Apr 24, 2020 at 10:12:10AM +0100, Burakov, Anatoly wrote:
> >>> On 23-Apr-20 9:04 PM, David Marchand wrote:
> >>>> On Thu, Apr 23, 2020 at 6:34 PM Burakov, Anatoly
> >>>> <anatoly.burakov@intel.com> wrote:
> >>>>>> diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
> >>>>>> index cc7d54e0c..2d9564b28 100644
> >>>>>> --- a/lib/librte_eal/common/eal_common_memory.c
> >>>>>> +++ b/lib/librte_eal/common/eal_common_memory.c
> >>>>>> @@ -177,6 +177,20 @@ 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.
> >>>>>> +              */
> >>>>>> +             if (madvise(aligned_addr, *size, MADV_DONTDUMP) != 0)
> >>>>>> +                     RTE_LOG(WARNING, EAL, "Madvise with MADV_DONTDUMP failed: %s\n",
> >>>>>> +                             strerror(errno));> +   } else {
> >>>>>> +             /*
> >>>>>> +              * Exclude this pages from a core dump.
> >>>>>> +              */
> >>>>>> +             if (madvise(mapped_addr, map_sz, MADV_DONTDUMP) != 0)
> >>>>>> +                     RTE_LOG(WARNING, EAL, "Madvise with MADV_DONTDUMP failed: %s\n",
> >>>>>> +                             strerror(errno));
> >>>>>>         }
> >>>>>>
> >>>>>>         return aligned_addr;
> >>>>>>
> >>>>>
> >>>>> For the contents of this patch,
> >>>>
> >>>> MADV_DONTDUMP does not seem POSIX, but as I said [1], there seems to
> >>>> be a MADV_NOCORE option on FreeBSD.
> >>>> 1: http://inbox.dpdk.org/dev/CAJFAV8y9YtT-7njUz+mD6U8+3XUqYrgp28KD7jy2923EpAcXrg@mail.gmail.com/
> >>>>
> >>>>
> >>>
> >>> Oh, right, so this would probably not compile on FreeBSD. Perhaps this
> >>> function would have to be OS-specific after all (or call into an OS-specific
> >>> madvise() after reserving the memory area).
> >>>
> >>
> >> Is it just a differently named flag? If so, I think a single #ifdef macro
> >> won't kill us in the common code.
> >>
> > Just the flag name is different.
> > I should use RTE_EXEC_ENV_FREEBSD and RTE_EXEC_ENV_LINUX, right?
>
> Yes, but we need this in two places, so a function call is still necessary.
>
> >
> > Another question, in `eal_memalloc.c:alloc_seg`, I should undo the
> > DONTMAP of the memory region.
> > Right? @Anatoly
>
> I don't think it's necessary. When you map different memory into that
> region, madvise() flags no longer apply. To be sure, i just tested this
> by adding another mmap() call after madvise() (in your test app) and
> remapping the same memory with MAP_FIXED, and the core dump was back to
> 1GB of size. So, no, i don't think you should undo anything - the system
> does so automatically.
Got it.
>
> >
> > Just few minutes, I have prepared a patch for the OS-specific code:
> > --- a/lib/librte_eal/common/eal_private.h
> > +++ b/lib/librte_eal/common/eal_private.h
> > @@ -443,4 +443,20 @@ rte_option_usage(void);
> >   uint64_t
> >   eal_get_baseaddr(void);
> >
> > +/**
> > + * @internal
> > + * Exclude this pages from a core dump.
> > + *
> > + * @param addr
> > + *  The memory region starts.
> > + *
> > + * @param len
> > + *  The memory region length..
> > + *
> > + * @return
> > + * returns 0 or -errno
> > + */
> > +int
> > +eal_madvise_dontdump(void* addr, size_t len);
> > +
> >   #endif /* _EAL_PRIVATE_H_ */
> > diff --git a/lib/librte_eal/freebsd/eal_memory.c
> > b/lib/librte_eal/freebsd/eal_memory.c
> > index a97d8f0f0..585042dde 100644
> > --- a/lib/librte_eal/freebsd/eal_memory.c
> > +++ b/lib/librte_eal/freebsd/eal_memory.c
> > @@ -534,3 +534,9 @@ rte_eal_memseg_init(void)
> >    memseg_primary_init() :
> >    memseg_secondary_init();
> >   }
> > +
> > +int
> > +eal_madvise_dontdump(void* addr, size_t len)
> > +{
> > + return madvise(addr, len, MADV_NOCORE);
> > +}
> > diff --git a/lib/librte_eal/linux/eal_memory.c
> > b/lib/librte_eal/linux/eal_memory.c
> > index 7a9c97ff8..cfdbfccfe 100644
> > --- a/lib/librte_eal/linux/eal_memory.c
> > +++ b/lib/librte_eal/linux/eal_memory.c
> > @@ -2479,3 +2479,9 @@ rte_eal_memseg_init(void)
> >   #endif
> >    memseg_secondary_init();
> >   }
> > +
> > +int
> > +eal_madvise_dontdump(void* addr, size_t len)
> > +{
> > + return madvise(addr, len, MADV_DONTDUMP);
> > +}
> >
>
> That would work as well (with added FreeBSD code of course), however if
> everyone else is OK with it, i'll settle for an #ifdef in common code.
>
> --
> Thanks,
> Anatoly

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