Re: hipe_mfait_lock

Hi Mikael,
Awesome work, I'll give the patch a try this week.

Thanks,
LP

On Mon, Feb 23, 2015 at 6:30 AM, Mikael Pettersson <[email protected]>
wrote:

> Louis-Philippe Gauthier writes:
>  > Hi Sverker,
>  > That's not a bad idea, I'll try that approach!
>  >
>  > Thanks,
>  > LP
>  >
>  > On Thu, Jan 15, 2015 at 12:27 AM, Sverker Eriksson <
>  > [email protected]> wrote:
>  >
>  > >  One quite simple improvement is to change the hipe_mfait_lock to be a
>  > > read-write mutex (erts_smp_rwmtx_t).
>  > > And then do read-lock at lookup and exclusive write-lock only when
>  > > inserting a new entry in the table.
>  > >
>  > > I don't think that requires much knowledge about the VM to pull off
> ;-) .
>  > >
>  > > /Sverker, Erlang/OTP
>  > >
>  > >
>  > >
>  > >
>  > > On 01/14/2015 12:34 AM, Louis-Philippe Gauthier wrote:
>  > >
>  > > Hi erlang-bugs,
>  > > I couple of months ago I tried running our full application using
> HiPE. I
>  > > ran into several issues, some manageable, some not... The most
> problematic
>  > > issue was due to locking, specifically, the hipe_mfait_lock (you can
> see
>  > > the lock counter output in the gist bellow).
>  > > https://gist.github.com/lpgauth/2b3220f4bceeed6f62d0
>  > >
>  > > Looking at the code it's obvious that this is a known problem... the
>  > > following comment was added when the lock was added in 2010.
>  > >
>  > > "XXX: Redesign apply et al to avoid those updates."
> https://github.com/erlang/otp/blob/maint/erts/emulator/hipe/hipe_bif0.c#L1218
>  > >
>  > > Unfortunately, I'm don't know the runtime enough to start patching
> it... so
>  > > instead I'm reporting it.
>
> Please try the attached patch (against 17.4, should apply to older
> versions too by I haven't checked), and let me know if it makes a
> noticeable improvement to your use case.
>
> Run-time apply:s now do their lookups using a shared read-lock, and
> only if their lookups fail do they re-lock with an exclusive write-lock
> in order to insert new data.  Module loading functions always take
> exclusive locks, which matches the current behaviour.
>
> /Mikael
>
>
> --- otp_src_17.4/erts/emulator/hipe/hipe_bif0.c.~1~     2014-12-09
> 21:11:07.000000000 +0100
> +++ otp_src_17.4/erts/emulator/hipe/hipe_bif0.c 2015-02-22
> 21:32:55.361884741 +0100
> @@ -1217,22 +1217,32 @@ static struct {
>       * they create a new stub for the mfa, which forces locking.
>       * XXX: Redesign apply et al to avoid those updates.
>       */
> -    erts_smp_mtx_t lock;
> +    erts_smp_rwmtx_t lock;
>  } hipe_mfa_info_table;
>
>  static inline void hipe_mfa_info_table_init_lock(void)
>  {
> -    erts_smp_mtx_init(&hipe_mfa_info_table.lock, "hipe_mfait_lock");
> +    erts_smp_rwmtx_init(&hipe_mfa_info_table.lock, "hipe_mfait_lock");
>  }
>
> -static inline void hipe_mfa_info_table_lock(void)
> +static inline void hipe_mfa_info_table_rlock(void)
>  {
> -    erts_smp_mtx_lock(&hipe_mfa_info_table.lock);
> +    erts_smp_rwmtx_rlock(&hipe_mfa_info_table.lock);
>  }
>
> -static inline void hipe_mfa_info_table_unlock(void)
> +static inline void hipe_mfa_info_table_runlock(void)
>  {
> -    erts_smp_mtx_unlock(&hipe_mfa_info_table.lock);
> +    erts_smp_rwmtx_runlock(&hipe_mfa_info_table.lock);
> +}
> +
> +static inline void hipe_mfa_info_table_rwlock(void)
> +{
> +    erts_smp_rwmtx_rwlock(&hipe_mfa_info_table.lock);
> +}
> +
> +static inline void hipe_mfa_info_table_rwunlock(void)
> +{
> +    erts_smp_rwmtx_rwunlock(&hipe_mfa_info_table.lock);
>  }
>
>  #define HIPE_MFA_HASH(M,F,A)   ((M) * (F) + (A))
> @@ -1333,6 +1343,7 @@ void *hipe_mfa_find_na(Eterm m, Eterm f,
>  }
>  #endif
>
> +/* PRE: called with write lock held */
>  static struct hipe_mfa_info *hipe_mfa_info_table_put_locked(Eterm m,
> Eterm f, unsigned int arity)
>  {
>      unsigned long h;
> @@ -1362,7 +1373,7 @@ static void hipe_mfa_set_na(Eterm m, Ete
>  {
>      struct hipe_mfa_info *p;
>
> -    hipe_mfa_info_table_lock();
> +    hipe_mfa_info_table_rwlock();
>      p = hipe_mfa_info_table_put_locked(m, f, arity);
>  #ifdef DEBUG_LINKER
>      printf("%s: ", __FUNCTION__);
> @@ -1372,7 +1383,7 @@ static void hipe_mfa_set_na(Eterm m, Ete
>      p->local_address = address;
>      if (is_exported)
>         p->remote_address = address;
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rwunlock();
>  }
>
>  #if defined(__powerpc__) || defined(__ppc__) || defined(__powerpc64__) ||
> defined(__arm__)
> @@ -1381,10 +1392,10 @@ void *hipe_mfa_get_trampoline(Eterm m, E
>      struct hipe_mfa_info *p;
>      void *trampoline;
>
> -    hipe_mfa_info_table_lock();
> -    p = hipe_mfa_info_table_put_locked(m, f, arity);
> -    trampoline = p->trampoline;
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rlock();
> +    p = hipe_mfa_info_table_get_locked(m, f, arity);
> +    trampoline = p ? p->trampoline : NULL;
> +    hipe_mfa_info_table_runlock();
>      return trampoline;
>  }
>
> @@ -1392,10 +1403,10 @@ void hipe_mfa_set_trampoline(Eterm m, Et
>  {
>      struct hipe_mfa_info *p;
>
> -    hipe_mfa_info_table_lock();
> +    hipe_mfa_info_table_rwlock();
>      p = hipe_mfa_info_table_put_locked(m, f, arity);
>      p->trampoline = trampoline;
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rwunlock();
>  }
>  #endif
>
> @@ -1426,7 +1437,7 @@ BIF_RETTYPE hipe_bifs_invalidate_funinfo
>      struct mfa mfa;
>      struct hipe_mfa_info *p;
>
> -    hipe_mfa_info_table_lock();
> +    hipe_mfa_info_table_rwlock();
>      lst = BIF_ARG_1;
>      while (is_list(lst)) {
>         if (!term_to_mfa(CAR(list_val(lst)), &mfa))
> @@ -1455,7 +1466,7 @@ BIF_RETTYPE hipe_bifs_invalidate_funinfo
>             }
>         }
>      }
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rwunlock();
>      if (is_not_nil(lst))
>         BIF_ERROR(BIF_P, BADARG);
>      BIF_RET(NIL);
> @@ -1469,7 +1480,7 @@ void hipe_mfa_save_orig_beam_op(Eterm mo
>      orig_beam_op = pc[0];
>      if (orig_beam_op != BeamOpCode(op_hipe_trap_call_closure) &&
>         orig_beam_op != BeamOpCode(op_hipe_trap_call)) {
> -       hipe_mfa_info_table_lock();
> +       hipe_mfa_info_table_rwlock();
>         p = hipe_mfa_info_table_put_locked(mod, fun, ari);
>  #ifdef DEBUG_LINKER
>         printf("%s: ", __FUNCTION__);
> @@ -1478,7 +1489,7 @@ void hipe_mfa_save_orig_beam_op(Eterm mo
>  #endif
>         p->beam_code = pc;
>         p->orig_beam_op = orig_beam_op;
> -       hipe_mfa_info_table_unlock();
> +       hipe_mfa_info_table_rwunlock();
>      } else {
>  #ifdef DEBUG_LINKER
>         printf("%s: ", __FUNCTION__);
> @@ -1505,7 +1516,8 @@ static void *hipe_make_stub(Eterm m, Ete
>      return StubAddress;
>  }
>
> -static void *hipe_get_na_nofail_locked(Eterm m, Eterm f, unsigned int a,
> int is_remote)
> +/* PRE: called with read or write lock held */
> +static void *hipe_get_na_try_locked(Eterm m, Eterm f, unsigned int a, int
> is_remote, struct hipe_mfa_info **pp)
>  {
>      struct hipe_mfa_info *p;
>      void *address;
> @@ -1523,7 +1535,20 @@ static void *hipe_get_na_nofail_locked(E
>         address = p->remote_address;
>         if (address)
>             return address;
> -    } else
> +    }
> +    /* Caller must take the slow path with the write lock held, but allow
> +       it to avoid some work if it already holds the write lock.  */
> +    if (pp)
> +       *pp = p;
> +    return NULL;
> +}
> +
> +/* PRE: called with write lock held */
> +static void *hipe_get_na_slow_locked(Eterm m, Eterm f, unsigned int a,
> int is_remote, struct hipe_mfa_info *p)
> +{
> +    void *address;
> +
> +    if (!p)
>         p = hipe_mfa_info_table_put_locked(m, f, a);
>      address = hipe_make_stub(m, f, a, is_remote);
>      /* XXX: how to tell if a BEAM MFA is exported or not? */
> @@ -1531,14 +1556,34 @@ static void *hipe_get_na_nofail_locked(E
>      return address;
>  }
>
> +/* PRE: called with write lock held */
> +static void *hipe_get_na_nofail_locked(Eterm m, Eterm f, unsigned int a,
> int is_remote)
> +{
> +    struct hipe_mfa_info *p /*= NULL*/;
> +    void *address;
> +
> +    address = hipe_get_na_try_locked(m, f, a, is_remote, &p);
> +    if (address)
> +       return address;
> +
> +    address = hipe_get_na_slow_locked(m, f, a, is_remote, p);
> +    return address;
> +}
> +
>  static void *hipe_get_na_nofail(Eterm m, Eterm f, unsigned int a, int
> is_remote)
>  {
> -    void *p;
> +    void *address;
>
> -    hipe_mfa_info_table_lock();
> -    p = hipe_get_na_nofail_locked(m, f, a, is_remote);
> -    hipe_mfa_info_table_unlock();
> -    return p;
> +    hipe_mfa_info_table_rlock();
> +    address = hipe_get_na_try_locked(m, f, a, is_remote, NULL);
> +    hipe_mfa_info_table_runlock();
> +    if (address)
> +       return address;
> +
> +    hipe_mfa_info_table_rwlock();
> +    address = hipe_get_na_slow_locked(m, f, a, is_remote, NULL);
> +    hipe_mfa_info_table_rwunlock();
> +    return address;
>  }
>
>  /* used for apply/3 in hipe_mode_switch */
> @@ -1617,7 +1662,7 @@ int hipe_find_mfa_from_ra(const void *ra
>      /* Note about locking: the table is only updated from the
>         loader, which runs with the rest of the system suspended. */
>      /* XXX: alas not true; see comment at hipe_mfa_info_table.lock */
> -    hipe_mfa_info_table_lock();
> +    hipe_mfa_info_table_rwlock();
>      bucket = hipe_mfa_info_table.bucket;
>      nrbuckets = 1 << hipe_mfa_info_table.log2size;
>      mfa = NULL;
> @@ -1638,7 +1683,7 @@ int hipe_find_mfa_from_ra(const void *ra
>         *f = mfa->f;
>         *a = mfa->a;
>      }
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rwunlock();
>      return mfa ? 1 : 0;
>  }
>
> @@ -1715,7 +1760,7 @@ BIF_RETTYPE hipe_bifs_add_ref_2(BIF_ALIS
>        default:
>         goto badarg;
>      }
> -    hipe_mfa_info_table_lock();
> +    hipe_mfa_info_table_rwlock();
>      callee_mfa = hipe_mfa_info_table_put_locked(callee.mod, callee.fun,
> callee.ari);
>      caller_mfa = hipe_mfa_info_table_put_locked(caller.mod, caller.fun,
> caller.ari);
>
> @@ -1731,7 +1776,7 @@ BIF_RETTYPE hipe_bifs_add_ref_2(BIF_ALIS
>      ref->flags = flags;
>      ref->next = callee_mfa->referred_from;
>      callee_mfa->referred_from = ref;
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rwunlock();
>
>      BIF_RET(NIL);
>
> @@ -1751,12 +1796,12 @@ BIF_RETTYPE hipe_bifs_mark_referred_from
>
>      if (!term_to_mfa(BIF_ARG_1, &mfa))
>         BIF_ERROR(BIF_P, BADARG);
> -    hipe_mfa_info_table_lock();
> +    hipe_mfa_info_table_rwlock();
>      p = hipe_mfa_info_table_get_locked(mfa.mod, mfa.fun, mfa.ari);
>      if (p)
>         for (ref = p->referred_from; ref != NULL; ref = ref->next)
>             ref->flags |= REF_FLAG_PENDING_REDIRECT;
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rwunlock();
>      BIF_RET(NIL);
>  }
>
> @@ -1770,7 +1815,7 @@ static void hipe_purge_all_refs(void)
>      struct hipe_mfa_info **bucket;
>      unsigned int i, nrbuckets;
>
> -    hipe_mfa_info_table_lock();
> +    hipe_mfa_info_table_rwlock();
>
>      bucket = hipe_mfa_info_table.bucket;
>      nrbuckets = 1 << hipe_mfa_info_table.log2size;
> @@ -1792,7 +1837,7 @@ static void hipe_purge_all_refs(void)
>             erts_free(ERTS_ALC_T_HIPE, mfa);
>         }
>      }
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rwunlock();
>  }
>
>  BIF_RETTYPE hipe_bifs_remove_refs_from_1(BIF_ALIST_1)
> @@ -1809,7 +1854,7 @@ BIF_RETTYPE hipe_bifs_remove_refs_from_1
>
>      if (!term_to_mfa(BIF_ARG_1, &mfa))
>         BIF_ERROR(BIF_P, BADARG);
> -    hipe_mfa_info_table_lock();
> +    hipe_mfa_info_table_rwlock();
>      caller_mfa = hipe_mfa_info_table_get_locked(mfa.mod, mfa.fun,
> mfa.ari);
>      if (caller_mfa) {
>         refers_to = caller_mfa->refers_to;
> @@ -1840,7 +1885,7 @@ BIF_RETTYPE hipe_bifs_remove_refs_from_1
>         }
>         caller_mfa->refers_to = NULL;
>      }
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rwunlock();
>      BIF_RET(am_ok);
>  }
>
> @@ -1859,7 +1904,7 @@ BIF_RETTYPE hipe_bifs_redirect_referred_
>
>      if (!term_to_mfa(BIF_ARG_1, &mfa))
>         BIF_ERROR(BIF_P, BADARG);
> -    hipe_mfa_info_table_lock();
> +    hipe_mfa_info_table_rwlock();
>      p = hipe_mfa_info_table_get_locked(mfa.mod, mfa.fun, mfa.ari);
>      if (p) {
>         prev = &p->referred_from;
> @@ -1890,7 +1935,7 @@ BIF_RETTYPE hipe_bifs_redirect_referred_
>             }
>         }
>      }
> -    hipe_mfa_info_table_unlock();
> +    hipe_mfa_info_table_rwunlock();
>      BIF_RET(NIL);
>  }
>
>
>

_______________________________________________
erlang-bugs mailing list
[email protected]
http://erlang.org/mailman/listinfo/erlang-bugs