Re: [dpdk-dev] [PATCH dpdk-dev v3 2/2] mempool: use shared memzone for rte_mempool_ops

[Tonghao Zhang <xiangxia.m.yue@gmail.com>]

On Thu, Apr 23, 2020 at 9:38 PM Andrew Rybchenko
<arybchenko@solarflare.com> wrote:
>
> On 4/13/20 5:21 PM, 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.
> >   but the number of mempool libraries may be different.
> >
> > * shared memzone: The primary process allocates a struct in
> >   shared memory named memzone, When we register a mempool ops,
> >   we first get a name and id from the shared struct: with the lock held,
> >   lookup for the registered name and return its index, else
> >   get the last id and copy the name in the struct.
> >
> > Previous discussion: https://mails.dpdk.org/archives/dev/2020-March/159354.html
> >
> > Suggested-by: Olivier Matz <olivier.matz@6wind.com>
> > Suggested-by: Jerin Jacob <jerinj@marvell.com>
> > Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
> > ---
> > v2:
> > * fix checkpatch warning
> > ---
> >  lib/librte_mempool/rte_mempool.h     | 28 +++++++++++-
> >  lib/librte_mempool/rte_mempool_ops.c | 89 ++++++++++++++++++++++++++++--------
> >  2 files changed, 96 insertions(+), 21 deletions(-)
> >
> > diff --git a/lib/librte_mempool/rte_mempool.h b/lib/librte_mempool/rte_mempool.h
> > index c90cf31467b2..2709b9e1d51b 100644
> > --- a/lib/librte_mempool/rte_mempool.h
> > +++ b/lib/librte_mempool/rte_mempool.h
> > @@ -50,6 +50,7 @@
> >  #include <rte_ring.h>
> >  #include <rte_memcpy.h>
> >  #include <rte_common.h>
> > +#include <rte_init.h>
> >
> >  #ifdef __cplusplus
> >  extern "C" {
> > @@ -678,7 +679,6 @@ struct rte_mempool_ops {
> >   */
> >  struct rte_mempool_ops_table {
> >       rte_spinlock_t sl;     /**< Spinlock for add/delete. */
> > -     uint32_t num_ops;      /**< Number of used ops structs in the table. */
> >       /**
> >        * Storage for all possible ops structs.
> >        */
> > @@ -910,6 +910,30 @@ int rte_mempool_ops_get_info(const struct rte_mempool *mp,
> >   */
> >  int rte_mempool_register_ops(const struct rte_mempool_ops *ops);
> >
> > +struct rte_mempool_shared_ops {
> > +     size_t num_mempool_ops;
>
> Is there any specific reason to change type from uint32_t used
> above to size_t? I think that uint32_t is better here since
> it is just a number, not a size of memory or related value.
Thanks for you review. busy to commit other patch, so that be delayed.
I will change that in next version.
> > +     struct {
> > +             char name[RTE_MEMPOOL_OPS_NAMESIZE];
> > +     } mempool_ops[RTE_MEMPOOL_MAX_OPS_IDX];
> > +
> > +     rte_spinlock_t mempool;
> > +};
> > +
> > +static inline int
> > +mempool_ops_register_cb(const void *arg)
> > +{
> > +     const struct rte_mempool_ops *h = (const struct rte_mempool_ops *)arg;
> > +
> > +     return rte_mempool_register_ops(h);
> > +}
> > +
> > +static inline void
> > +mempool_ops_register(const struct rte_mempool_ops *ops)
> > +{
> > +     rte_init_register(mempool_ops_register_cb, (const void *)ops,
> > +                       RTE_INIT_PRE);
> > +}
> > +
> >  /**
> >   * Macro to statically register the ops of a mempool handler.
> >   * Note that the rte_mempool_register_ops fails silently here when
> > @@ -918,7 +942,7 @@ int rte_mempool_ops_get_info(const struct rte_mempool *mp,
> >  #define MEMPOOL_REGISTER_OPS(ops)                            \
> >       RTE_INIT(mp_hdlr_init_##ops)                            \
> >       {                                                       \
> > -             rte_mempool_register_ops(&ops);                 \
> > +             mempool_ops_register(&ops);                     \
> >       }
> >
> >  /**
> > diff --git a/lib/librte_mempool/rte_mempool_ops.c b/lib/librte_mempool/rte_mempool_ops.c
> > index 22c5251eb068..b10fda662db6 100644
> > --- a/lib/librte_mempool/rte_mempool_ops.c
> > +++ b/lib/librte_mempool/rte_mempool_ops.c
> > @@ -14,43 +14,95 @@
> >  /* indirect jump table to support external memory pools. */
> >  struct rte_mempool_ops_table rte_mempool_ops_table = {
> >       .sl =  RTE_SPINLOCK_INITIALIZER,
> > -     .num_ops = 0
> >  };
> >
> > -/* add a new ops struct in rte_mempool_ops_table, return its index. */
> > -int
> > -rte_mempool_register_ops(const struct rte_mempool_ops *h)
> > +static int
> > +rte_mempool_register_shared_ops(const char *name)
> >  {
> > -     struct rte_mempool_ops *ops;
> > -     int16_t ops_index;
> > +     static bool mempool_shared_ops_inited;
> > +     struct rte_mempool_shared_ops *shared_ops;
> > +     const struct rte_memzone *mz;
> > +     uint32_t ops_index = 0;
> > +
>
> I think we should sanity check 'name' here to be not
> empty string (see review notes below).
OK
> > +     if (rte_eal_process_type() == RTE_PROC_PRIMARY &&
> > +         !mempool_shared_ops_inited) {
> > +
> > +             mz = rte_memzone_reserve("mempool_ops_shared",
> > +                                      sizeof(*shared_ops), 0, 0);
> > +             if (mz == NULL)
> > +                     return -ENOMEM;
> > +
> > +             shared_ops = mz->addr;
> > +             shared_ops->num_mempool_ops = 0;
> > +             rte_spinlock_init(&shared_ops->mempool);
> > +
> > +             mempool_shared_ops_inited = true;
> > +     } else {
> > +             mz = rte_memzone_lookup("mempool_ops_shared");
> > +             if (mz == NULL)
> > +                     return -ENOMEM;
> > +
> > +             shared_ops = mz->addr;
> > +     }
> >
> > -     rte_spinlock_lock(&rte_mempool_ops_table.sl);
> > +     rte_spinlock_lock(&shared_ops->mempool);
> >
> > -     if (rte_mempool_ops_table.num_ops >=
> > -                     RTE_MEMPOOL_MAX_OPS_IDX) {
> > -             rte_spinlock_unlock(&rte_mempool_ops_table.sl);
> > +     if (shared_ops->num_mempool_ops >= RTE_MEMPOOL_MAX_OPS_IDX) {
> > +             rte_spinlock_unlock(&shared_ops->mempool);
> >               RTE_LOG(ERR, MEMPOOL,
> >                       "Maximum number of mempool ops structs exceeded\n");
> >               return -ENOSPC;
> >       }
> >
> > +     while (shared_ops->mempool_ops[ops_index].name[0]) {
>
> Please, compare with '\0' as DPDK style guide says.
>
> > +             if (!strcmp(name, shared_ops->mempool_ops[ops_index].name)) {
> > +                     rte_spinlock_unlock(&shared_ops->mempool);
> > +                     return ops_index;
> > +             }
> > +
> > +             ops_index++;
> > +     }
> > +
> > +     strlcpy(shared_ops->mempool_ops[ops_index].name, name,
> > +             sizeof(shared_ops->mempool_ops[0].name));
> > +
> > +     shared_ops->num_mempool_ops++;
> > +
> > +     rte_spinlock_unlock(&shared_ops->mempool);
> > +     return ops_index;
> > +}
> > +
> > +/* add a new ops struct in rte_mempool_ops_table, return its index. */
> > +int
> > +rte_mempool_register_ops(const struct rte_mempool_ops *h)
> > +{
> > +     struct rte_mempool_ops *ops;
> > +     int16_t ops_index;
> > +
> >       if (h->alloc == NULL || h->enqueue == NULL ||
> > -                     h->dequeue == NULL || h->get_count == NULL) {
> > -             rte_spinlock_unlock(&rte_mempool_ops_table.sl);
> > +         h->dequeue == NULL || h->get_count == NULL) {
>
> Changing formatting just makes review a bit more harder.
>
> >               RTE_LOG(ERR, MEMPOOL,
> >                       "Missing callback while registering mempool ops\n");
> > +             rte_errno = EINVAL;
>
> Why is it done in the patch? For me it looks like logically
> different change if it is really required (properly motivated).
I guess that should add the err code to rte_rrno ? but I am fine, not
to do that.
> >               return -EINVAL;
> >       }
> >
> >       if (strlen(h->name) >= sizeof(ops->name) - 1) {
> > -             rte_spinlock_unlock(&rte_mempool_ops_table.sl);
> > -             RTE_LOG(DEBUG, EAL, "%s(): mempool_ops <%s>: name too long\n",
> > -                             __func__, h->name);
> > +             RTE_LOG(ERR, MEMPOOL,
> > +                     "The registering  mempool_ops <%s>: name too long\n",
> > +                     h->name);
>
> Why do you change from DEBUG to ERR here? It it not
> directly related to the purpose of the patch.
Yes, because it is an error, so change that type. I change it in
separate patch ?
> >               rte_errno = EEXIST;
> >               return -EEXIST;
> >       }
> >
> > -     ops_index = rte_mempool_ops_table.num_ops++;
> > +     ops_index = rte_mempool_register_shared_ops(h->name);
> > +     if (ops_index < 0) {
> > +             rte_errno = -ops_index;
> > +             return ops_index;
> > +     }
> > +
> > +     rte_spinlock_lock(&rte_mempool_ops_table.sl);
> > +
> >       ops = &rte_mempool_ops_table.ops[ops_index];
> >       strlcpy(ops->name, h->name, sizeof(ops->name));
> >       ops->alloc = h->alloc;
> > @@ -165,9 +217,8 @@ struct rte_mempool_ops_table rte_mempool_ops_table = {
> >       if (mp->flags & MEMPOOL_F_POOL_CREATED)
> >               return -EEXIST;
> >
> > -     for (i = 0; i < rte_mempool_ops_table.num_ops; i++) {
> > -             if (!strcmp(name,
> > -                             rte_mempool_ops_table.ops[i].name)) {
> > +     for (i = 0; i < RTE_MEMPOOL_MAX_OPS_IDX; i++) {
> > +             if (!strcmp(name, rte_mempool_ops_table.ops[i].name)) {
>
> Since rte_mempool_ops_table is filled in which zeros,
> name string is empty by default. So, request with empty name
> will match the first unused entry. I guess it is not what we
> want here. I think we should handle empty string before the
> loop and return -EINVAL.
OK, thanks.
> >                       ops = &rte_mempool_ops_table.ops[i];
> >                       break;
> >               }
> >
>


-- 
Best regards, Tonghao