Re: [dpdk-dev] [PATCH] mempool: sort the rte_mempool_ops by name

[Jerin Jacob <jerinjacobk@gmail.com>]

On Wed, Mar 4, 2020 at 8:17 PM Tonghao Zhang <xiangxia.m.yue@gmail.com> wrote:
>
> On Wed, Mar 4, 2020 at 9:33 PM Jerin Jacob <jerinjacobk@gmail.com> wrote:
> >
> > On Wed, Mar 4, 2020 at 6:48 PM Tonghao Zhang <xiangxia.m.yue@gmail.com> wrote:
> > >
> > > On Mon, Mar 2, 2020 at 9:45 PM Jerin Jacob <jerinjacobk@gmail.com> wrote:
> > > >
> > > > On Mon, Mar 2, 2020 at 7:27 AM <xiangxia.m.yue@gmail.com> wrote:
> > > > >
> > > > > From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
> > > > >
> > > > > The order of mempool initiation affects mempool index in the
> > > > > rte_mempool_ops_table. For example, when building APPs with:
> > > > >
> > > > > $ gcc -lrte_mempool_bucket -lrte_mempool_ring ...
> > > > >
> > > > > The "bucket" mempool will be registered firstly, and its index
> > > > > in table is 0 while the index of "ring" mempool is 1. DPDK
> > > > > uses the mk/rte.app.mk to build APPs, and others, for example,
> > > > > Open vSwitch, use the libdpdk.a or libdpdk.so to build it.
> > > > > The mempool lib linked in dpdk and Open vSwitch is different.
> > > > >
> > > > > The mempool can be used between primary and secondary process,
> > > > > such as dpdk-pdump and pdump-pmd/Open vSwitch(pdump enabled).
> > > > > There will be a crash because dpdk-pdump creates the "ring_mp_mc"
> > > > > ring which index in table is 0, but the index of "bucket" ring
> > > > > is 0 in Open vSwitch. If Open vSwitch use the index 0 to get
> > > > > mempool ops and malloc memory from mempool. The crash will occur:
> > > > >
> > > > >     bucket_dequeue (access null and crash)
> > > > >     rte_mempool_get_ops (should get "ring_mp_mc",
> > > > >                          but get "bucket" mempool)
> > > > >     rte_mempool_ops_dequeue_bulk
> > > > >     ...
> > > > >     rte_pktmbuf_alloc
> > > > >     rte_pktmbuf_copy
> > > > >     pdump_copy
> > > > >     pdump_rx
> > > > >     rte_eth_rx_burst
> > > > >
> > > > > To avoid the crash, there are some solution:
> > > > > * constructor priority: Different mempool uses different
> > > > >   priority in RTE_INIT, but it's not easy to maintain.
> > > > >
> > > > > * change mk/rte.app.mk: Change the order in mk/rte.app.mk to
> > > > >   be same as libdpdk.a/libdpdk.so, but when adding a new mempool
> > > > >   driver in future, we must make sure the order.
> > > > >
> > > > > * register mempool orderly: Sort the mempool when registering,
> > > > >   so the lib linked will not affect the index in mempool table.
> > > > >
> > > > > Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
> > > > > ---
> > > > >  lib/librte_mempool/rte_mempool_ops.c | 18 ++++++++++++++++--
> > > > >  1 file changed, 16 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/lib/librte_mempool/rte_mempool_ops.c b/lib/librte_mempool/rte_mempool_ops.c
> > > > > index 22c5251..06dfe16 100644
> > > > > --- a/lib/librte_mempool/rte_mempool_ops.c
> > > > > +++ b/lib/librte_mempool/rte_mempool_ops.c
> > > > > @@ -22,7 +22,7 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
> > > > >  rte_mempool_register_ops(const struct rte_mempool_ops *h)
> > > > >  {
> > > > >         struct rte_mempool_ops *ops;
> > > > > -       int16_t ops_index;
> > > > > +       unsigned ops_index, i;
> > > > >
> > > > >         rte_spinlock_lock(&rte_mempool_ops_table.sl);
> > > > >
> > > > > @@ -50,7 +50,19 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
> > > > >                 return -EEXIST;
> > > > >         }
> > > > >
> > > > > -       ops_index = rte_mempool_ops_table.num_ops++;
> > > > > +       /* sort the rte_mempool_ops by name. the order of the mempool
> > > > > +        * lib initiation will not affect rte_mempool_ops index. */
> > > >
> > > > +1 for the fix.
> > > > For the implementation, why not use qsort_r() for sorting?
> > > The implementation is easy, and the number of mempool driver is not too large.
> > > But we can use the qsort_r to implement it.
> >
> > Since it is in a slow path, IMO, better to use standard sort functions
> > for better readability.
> Agree, can you help me review the patch:
>
> diff --git a/lib/librte_mempool/rte_mempool_ops.c
> b/lib/librte_mempool/rte_mempool_ops.c
> index 22c5251..1acee58 100644
> --- a/lib/librte_mempool/rte_mempool_ops.c
> +++ b/lib/librte_mempool/rte_mempool_ops.c
> @@ -17,6 +17,15 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
>         .num_ops = 0
>  };
>
> +static int
> +compare_mempool_ops(const void *a, const void *b)
> +{
> +       const struct rte_mempool_ops *m_a = a;
> +       const struct rte_mempool_ops *m_b = b;
> +
> +       return strcmp(m_a->name, m_b->name);
> +}
> +
>  /* add a new ops struct in rte_mempool_ops_table, return its index. */
>  int
>  rte_mempool_register_ops(const struct rte_mempool_ops *h)
> @@ -63,6 +72,9 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
>         ops->get_info = h->get_info;
>         ops->dequeue_contig_blocks = h->dequeue_contig_blocks;
>
> +       qsort(rte_mempool_ops_table.ops, rte_mempool_ops_table.num_ops,
> +             sizeof(rte_mempool_ops_table.ops[0]), compare_mempool_ops);

Looks good.

Not tested. Please check qsort behavior when
rte_mempool_ops_table.num_ops == 0 case.



> +
>         rte_spinlock_unlock(&rte_mempool_ops_table.sl);
>
>         return ops_index;
>
>
> >
> > > >
> > > > > +       ops_index = rte_mempool_ops_table.num_ops;
> > > > > +       for (i = 0; i < rte_mempool_ops_table.num_ops; i++) {
> > > > > +               if (strcmp(h->name, rte_mempool_ops_table.ops[i].name) < 0) {
> > > > > +                       do {
> > > > > +                               rte_mempool_ops_table.ops[ops_index] =
> > > > > +                                       rte_mempool_ops_table.ops[ops_index -1];
> > > > > +                       } while (--ops_index > i);
> > > > > +                       break;
> > > > > +               }
> > > > > +       }
> > > > > +
> > > > >         ops = &rte_mempool_ops_table.ops[ops_index];
> > > > >         strlcpy(ops->name, h->name, sizeof(ops->name));
> > > > >         ops->alloc = h->alloc;
> > > > > @@ -63,6 +75,8 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
> > > > >         ops->get_info = h->get_info;
> > > > >         ops->dequeue_contig_blocks = h->dequeue_contig_blocks;
> > > > >
> > > > > +       rte_mempool_ops_table.num_ops++;
> > > > > +
> > > > >         rte_spinlock_unlock(&rte_mempool_ops_table.sl);
> > > > >
> > > > >         return ops_index;
> > > > > --
> > > > > 1.8.3.1
> > > > >
> > >
> > >
> > >
> > > --
> > > Thanks,
> > > Tonghao
>
>
>
> --
> Thanks,
> Tonghao