[PATCH v2] eal: change alloc_sz calculation which may cause unnecessarily allocation

[David Marchand]

On Thu, Sep 22, 2022 at 12:52 AM Dmitry Kozlyuk
<dmitry.kozliuk at gmail.com> wrote:
>
> 2022-09-21 15:35 (UTC+0200), David Marchand:
> > On Thu, Jul 28, 2022 at 8:03 PM Dmitry Kozlyuk <dmitry.kozliuk at gmail.com> wrote:
> > >
> > > 2022-07-28 14:41 (UTC+0500), Fidaullah Noonari:
> > > > The amount of memory to allocate from the system for heap expansion
> > > > was calculated in a way that may yield one page more than needed.
> > > > This could hit the allocation limit from the system or EAL.
> > > > The allocation would fail despite enough memory being available.
> > > >
> > > > In response to mail:
> > > > http://inbox.dpdk.org/dev/CAEYuUWCnRZNwxiOHEeTHw0Gy9aFJRLZtvAG9g=smuUvUEMcFXg@mail.gmail.com/
> > > >
> > > > Signed-off-by: Fidaullah Noonari <fidaullah.noonari at emumba.com>
> > >
> > > Acked-by: Dmitry Kozlyuk <dmitry.kozliuk at gmail.com>
> > >
> >
> > Do you have a reproducer?
> > This sounds like a fix, should we backport it?
>
> We should, thanks for the catch.
>
> Reproducer:
>
> #include <rte_eal.h>
> #include <rte_malloc.h>
> #include <stdio.h>
>
> int
> main(int argc, char **argv)
> {
>         static const size_t hugepage_sz = 2 * (1 << 20);
>         static const size_t malloc_elem_overhead = 128;
>         static const size_t size = hugepage_sz - malloc_elem_overhead;
>         struct rte_malloc_socket_stats stats_before, stats_after;
>         size_t alloc_delta;
>         int ret;
>
>         ret = rte_eal_init(argc, argv);
>         if (ret < 0)
>                 rte_panic("Cannot init EAL\n");
>         rte_malloc_get_socket_stats(0, &stats_before);
>         (void)rte_malloc(NULL, size, 0);
>         rte_malloc_get_socket_stats(0, &stats_after);
>         alloc_delta = stats_after.heap_totalsz_bytes - stats_before.heap_totalsz_bytes;
>         puts(alloc_delta == hugepage_sz ? "fixed" : "affected");
>         rte_eal_cleanup();
>         return 0;

Thanks Dmitry.
I'll put a note about this reproducer in the commitlog.

> }
>


-- 
David Marchand