Re: [dpdk-dev] [dpdk-stable] [PATCH 2/2] malloc: fix realloc padded element size

["Xueming(Steven) Li" <xuemingl@mellanox.com>]

Hi Anatoly,

> -----Original Message-----
> From: Burakov, Anatoly <anatoly.burakov@intel.com>
> Sent: Thursday, November 21, 2019 8:30 PM
> To: David Marchand <david.marchand@redhat.com>; Xueming(Steven) Li
> <xuemingl@mellanox.com>
> Cc: Asaf Penso <asafp@mellanox.com>; dev <dev@dpdk.org>; dpdk stable
> <stable@dpdk.org>
> Subject: Re: [dpdk-stable] [PATCH 2/2] malloc: fix realloc padded element size
> 
> On 20-Nov-19 1:25 PM, David Marchand wrote:
> > On Wed, Nov 20, 2019 at 3:12 AM Xueming(Steven) Li
> > <xuemingl@mellanox.com> wrote:
> >>
> >>> -----Original Message-----
> >>> From: David Marchand <david.marchand@redhat.com>
> >>> Sent: Wednesday, November 20, 2019 4:47 AM
> >>> To: Xueming(Steven) Li <xuemingl@mellanox.com>; Anatoly Burakov
> >>> <anatoly.burakov@intel.com>
> >>> Cc: Asaf Penso <asafp@mellanox.com>; dev <dev@dpdk.org>; dpdk stable
> >>> <stable@dpdk.org>
> >>> Subject: Re: [dpdk-stable] [PATCH 2/2] malloc: fix realloc padded
> >>> element size
> >>>
> >>> On Tue, Nov 12, 2019 at 3:50 PM Xueming Li <xuemingl@mellanox.com>
> >>> wrote:
> >>>>
> >>>> When resize a memory with next element, the original element size grows.
> >>>> If the orginal element has padding, the real inner element size
> >>>> didn't grow as well and this causes trailer verification failure
> >>>> when malloc debug enabled.
> >>>
> >>> I did not see this when running the malloc_autotest with debug enabled.
> >>> What is missing for me to catch it?
> >>>
> >> Yes, it happens rarely, depends on memory fragment. I only caught this in
> middle of a long test.
> >>
> >>>
> >>> Just a bit chilly to apply this series.
> >>> The first patch seems an optimisation.
> >>> The second one seems more interesting if we fix the debug mode, but
> >>> I suppose we can live without them in 19.11.
> >> Few people enable memory debug option, they are there for years.
> >
> > Had a discussion offlist with Anatoly.
> > Those two issues are hard to catch but the fixes are relevant and
> > Anatoly is confident.
> > I will take this in rc3.
> >
> > Series applied, thanks.
> >
> 
> To test them, i had to modify malloc to always create padded elements :)

I fix another issue in element join, as I made some local enhancement patch on memory, it's required, not sure whether it help on public code.

diff --git a/lib/librte_eal/common/malloc_elem.c b/lib/librte_eal/common/malloc_elem.c
index afacb1813c..c3fa0d1039 100644
--- a/lib/librte_eal/common/malloc_elem.c
+++ b/lib/librte_eal/common/malloc_elem.c
@@ -487,6 +487,10 @@ join_elem(struct malloc_elem *elem1, struct malloc_elem *elem2)
        else
                elem1->heap->last = elem1;
        elem1->next = next;
+       if (elem1->pad) {
+               struct malloc_elem *inner = RTE_PTR_ADD(elem1, elem1->pad);
+               inner->size += elem2->size;
+       }
 }



> 
> --
> Thanks,
> Anatoly