[v3] mbuf: use C11 atomic built-ins for refcnt operations
diff mbox series

Message ID 1594289442-18594-1-git-send-email-phil.yang@arm.com
State Superseded
Delegated to: David Marchand
Headers show
Series
  • [v3] mbuf: use C11 atomic built-ins for refcnt operations
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ci/checkpatch success coding style OK

Commit Message

Phil Yang July 9, 2020, 10:10 a.m. UTC
Use C11 atomic built-ins with explicit ordering instead of rte_atomic
ops which enforce unnecessary barriers on aarch64.

Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
v3:
1.Fix ABI breakage.
2.Simplify data type cast.

v2:
Fix ABI issue: revert the rte_mbuf_ext_shared_info struct refcnt field
to refcnt_atomic.

 lib/librte_mbuf/rte_mbuf.c      |  1 -
 lib/librte_mbuf/rte_mbuf.h      | 19 ++++++++++---------
 lib/librte_mbuf/rte_mbuf_core.h |  2 +-
 3 files changed, 11 insertions(+), 11 deletions(-)

Comments

Olivier Matz July 9, 2020, 11:03 a.m. UTC | #1
Hi Phil,

On Thu, Jul 09, 2020 at 06:10:42PM +0800, Phil Yang wrote:
> Use C11 atomic built-ins with explicit ordering instead of rte_atomic
> ops which enforce unnecessary barriers on aarch64.
> 
> Signed-off-by: Phil Yang <phil.yang@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
> v3:
> 1.Fix ABI breakage.
> 2.Simplify data type cast.
> 
> v2:
> Fix ABI issue: revert the rte_mbuf_ext_shared_info struct refcnt field
> to refcnt_atomic.
> 
>  lib/librte_mbuf/rte_mbuf.c      |  1 -
>  lib/librte_mbuf/rte_mbuf.h      | 19 ++++++++++---------
>  lib/librte_mbuf/rte_mbuf_core.h |  2 +-
>  3 files changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
> index ae91ae2..8a456e5 100644
> --- a/lib/librte_mbuf/rte_mbuf.c
> +++ b/lib/librte_mbuf/rte_mbuf.c
> @@ -22,7 +22,6 @@
>  #include <rte_eal.h>
>  #include <rte_per_lcore.h>
>  #include <rte_lcore.h>
> -#include <rte_atomic.h>
>  #include <rte_branch_prediction.h>
>  #include <rte_mempool.h>
>  #include <rte_mbuf.h>
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index f8e492e..c1c0956 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -37,7 +37,6 @@
>  #include <rte_config.h>
>  #include <rte_mempool.h>
>  #include <rte_memory.h>
> -#include <rte_atomic.h>
>  #include <rte_prefetch.h>
>  #include <rte_branch_prediction.h>
>  #include <rte_byteorder.h>
> @@ -365,7 +364,7 @@ rte_pktmbuf_priv_flags(struct rte_mempool *mp)
>  static inline uint16_t
>  rte_mbuf_refcnt_read(const struct rte_mbuf *m)
>  {
> -	return (uint16_t)(rte_atomic16_read(&m->refcnt_atomic));
> +	return __atomic_load_n(&m->refcnt, __ATOMIC_RELAXED);
>  }
>  
>  /**
> @@ -378,14 +377,15 @@ rte_mbuf_refcnt_read(const struct rte_mbuf *m)
>  static inline void
>  rte_mbuf_refcnt_set(struct rte_mbuf *m, uint16_t new_value)
>  {
> -	rte_atomic16_set(&m->refcnt_atomic, (int16_t)new_value);
> +	__atomic_store_n(&m->refcnt, new_value, __ATOMIC_RELAXED);
>  }
>  
>  /* internal */
>  static inline uint16_t
>  __rte_mbuf_refcnt_update(struct rte_mbuf *m, int16_t value)
>  {
> -	return (uint16_t)(rte_atomic16_add_return(&m->refcnt_atomic, value));
> +	return __atomic_add_fetch(&m->refcnt, (uint16_t)value,
> +				 __ATOMIC_ACQ_REL);
>  }
>  
>  /**
> @@ -466,7 +466,7 @@ rte_mbuf_refcnt_set(struct rte_mbuf *m, uint16_t new_value)
>  static inline uint16_t
>  rte_mbuf_ext_refcnt_read(const struct rte_mbuf_ext_shared_info *shinfo)
>  {
> -	return (uint16_t)(rte_atomic16_read(&shinfo->refcnt_atomic));
> +	return __atomic_load_n(&shinfo->refcnt_atomic, __ATOMIC_RELAXED);
>  }
>  
>  /**
> @@ -481,7 +481,7 @@ static inline void
>  rte_mbuf_ext_refcnt_set(struct rte_mbuf_ext_shared_info *shinfo,
>  	uint16_t new_value)
>  {
> -	rte_atomic16_set(&shinfo->refcnt_atomic, (int16_t)new_value);
> +	__atomic_store_n(&shinfo->refcnt_atomic, new_value, __ATOMIC_RELAXED);
>  }
>  
>  /**
> @@ -505,7 +505,8 @@ rte_mbuf_ext_refcnt_update(struct rte_mbuf_ext_shared_info *shinfo,
>  		return (uint16_t)value;
>  	}
>  
> -	return (uint16_t)rte_atomic16_add_return(&shinfo->refcnt_atomic, value);
> +	return __atomic_add_fetch(&shinfo->refcnt_atomic, (uint16_t)value,
> +				 __ATOMIC_ACQ_REL);
>  }
>  
>  /** Mbuf prefetch */
> @@ -1304,8 +1305,8 @@ static inline int __rte_pktmbuf_pinned_extbuf_decref(struct rte_mbuf *m)
>  	 * Direct usage of add primitive to avoid
>  	 * duplication of comparing with one.
>  	 */
> -	if (likely(rte_atomic16_add_return
> -			(&shinfo->refcnt_atomic, -1)))
> +	if (likely(__atomic_add_fetch(&shinfo->refcnt_atomic, (uint16_t)-1,
> +				     __ATOMIC_ACQ_REL)))
>  		return 1;
>  
>  	/* Reinitialize counter before mbuf freeing. */
> diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h
> index 16600f1..d65d1c8 100644
> --- a/lib/librte_mbuf/rte_mbuf_core.h
> +++ b/lib/librte_mbuf/rte_mbuf_core.h
> @@ -679,7 +679,7 @@ typedef void (*rte_mbuf_extbuf_free_callback_t)(void *addr, void *opaque);
>  struct rte_mbuf_ext_shared_info {
>  	rte_mbuf_extbuf_free_callback_t free_cb; /**< Free callback function */
>  	void *fcb_opaque;                        /**< Free callback argument */
> -	rte_atomic16_t refcnt_atomic;        /**< Atomically accessed refcnt */
> +	uint16_t refcnt_atomic;              /**< Atomically accessed refcnt */
>  };

To avoid an API breakage (i.e. currently, an application that accesses
to refcnt_atomic expects that its type is rte_atomic16_t), I suggest to
do the same than in the mbuf struct:

	union {
		rte_atomic16_t refcnt_atomic;
		uint16_t refcnt;
	};

I hope the ABI checker won't complain.

It will also be better for 20.11 when the deprecated fields will be
renamed: the remaining one will be called 'refcnt' in both mbuf and
mbuf_ext_shared_info.


Olivier
Phil Yang July 9, 2020, 1 p.m. UTC | #2
Hi Oliver,

> -----Original Message-----
> From: Olivier Matz <olivier.matz@6wind.com>
> Sent: Thursday, July 9, 2020 7:04 PM
> To: Phil Yang <Phil.Yang@arm.com>
> Cc: dev@dpdk.org; stephen@networkplumber.org;
> david.marchand@redhat.com; drc@linux.vnet.ibm.com; Honnappa
> Nagarahalli <Honnappa.Nagarahalli@arm.com>; Ruifeng Wang
> <Ruifeng.Wang@arm.com>; nd <nd@arm.com>
> Subject: Re: [PATCH v3] mbuf: use C11 atomic built-ins for refcnt operations
> 
> Hi Phil,
> 
> On Thu, Jul 09, 2020 at 06:10:42PM +0800, Phil Yang wrote:
> > Use C11 atomic built-ins with explicit ordering instead of rte_atomic
> > ops which enforce unnecessary barriers on aarch64.
> >
> > Signed-off-by: Phil Yang <phil.yang@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > ---
> > v3:
> > 1.Fix ABI breakage.
> > 2.Simplify data type cast.
> >
> > v2:
> > Fix ABI issue: revert the rte_mbuf_ext_shared_info struct refcnt field
> > to refcnt_atomic.
> >
> >  lib/librte_mbuf/rte_mbuf.c      |  1 -
> >  lib/librte_mbuf/rte_mbuf.h      | 19 ++++++++++---------
> >  lib/librte_mbuf/rte_mbuf_core.h |  2 +-
> >  3 files changed, 11 insertions(+), 11 deletions(-)
> >
<snip>
> >
> >  	/* Reinitialize counter before mbuf freeing. */
> > diff --git a/lib/librte_mbuf/rte_mbuf_core.h
> b/lib/librte_mbuf/rte_mbuf_core.h
> > index 16600f1..d65d1c8 100644
> > --- a/lib/librte_mbuf/rte_mbuf_core.h
> > +++ b/lib/librte_mbuf/rte_mbuf_core.h
> > @@ -679,7 +679,7 @@ typedef void
> (*rte_mbuf_extbuf_free_callback_t)(void *addr, void *opaque);
> >  struct rte_mbuf_ext_shared_info {
> >  	rte_mbuf_extbuf_free_callback_t free_cb; /**< Free callback
> function */
> >  	void *fcb_opaque;                        /**< Free callback argument */
> > -	rte_atomic16_t refcnt_atomic;        /**< Atomically accessed refcnt */
> > +	uint16_t refcnt_atomic;              /**< Atomically accessed refcnt */
> >  };
> 
> To avoid an API breakage (i.e. currently, an application that accesses
> to refcnt_atomic expects that its type is rte_atomic16_t), I suggest to
> do the same than in the mbuf struct:
> 
> 	union {
> 		rte_atomic16_t refcnt_atomic;
> 		uint16_t refcnt;
> 	};
> 
> I hope the ABI checker won't complain.
> 
> It will also be better for 20.11 when the deprecated fields will be
> renamed: the remaining one will be called 'refcnt' in both mbuf and
> mbuf_ext_shared_info.

Got it. I agree with you.
It should work. In my local test machine, the ABI checker happy with this approach. 
Once the test is done, I will upstream the new patch.

Appreciate your comments.

Thanks,
Phil
Honnappa Nagarahalli July 9, 2020, 1:31 p.m. UTC | #3
<snip>

> >
> > Hi Phil,
> >
> > On Thu, Jul 09, 2020 at 06:10:42PM +0800, Phil Yang wrote:
> > > Use C11 atomic built-ins with explicit ordering instead of
> > > rte_atomic ops which enforce unnecessary barriers on aarch64.
> > >
> > > Signed-off-by: Phil Yang <phil.yang@arm.com>
> > > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > > ---
> > > v3:
> > > 1.Fix ABI breakage.
> > > 2.Simplify data type cast.
> > >
> > > v2:
> > > Fix ABI issue: revert the rte_mbuf_ext_shared_info struct refcnt
> > > field to refcnt_atomic.
> > >
> > >  lib/librte_mbuf/rte_mbuf.c      |  1 -
> > >  lib/librte_mbuf/rte_mbuf.h      | 19 ++++++++++---------
> > >  lib/librte_mbuf/rte_mbuf_core.h |  2 +-
> > >  3 files changed, 11 insertions(+), 11 deletions(-)
> > >
> <snip>
> > >
> > >  /* Reinitialize counter before mbuf freeing. */ diff --git
> > > a/lib/librte_mbuf/rte_mbuf_core.h
> > b/lib/librte_mbuf/rte_mbuf_core.h
> > > index 16600f1..d65d1c8 100644
> > > --- a/lib/librte_mbuf/rte_mbuf_core.h
> > > +++ b/lib/librte_mbuf/rte_mbuf_core.h
> > > @@ -679,7 +679,7 @@ typedef void
> > (*rte_mbuf_extbuf_free_callback_t)(void *addr, void *opaque);
> > >  struct rte_mbuf_ext_shared_info {
> > >  rte_mbuf_extbuf_free_callback_t free_cb; /**< Free callback
> > function */
> > >  void *fcb_opaque;                        /**< Free callback argument */
> > > -rte_atomic16_t refcnt_atomic;        /**< Atomically accessed refcnt */
> > > +uint16_t refcnt_atomic;              /**< Atomically accessed refcnt */
> > >  };
> >
> > To avoid an API breakage (i.e. currently, an application that accesses
> > to refcnt_atomic expects that its type is rte_atomic16_t), I suggest
> > to do the same than in the mbuf struct:
> >
> > union {
> > rte_atomic16_t refcnt_atomic;
> > uint16_t refcnt;
> > };
> >
> > I hope the ABI checker won't complain.
> >
> > It will also be better for 20.11 when the deprecated fields will be
> > renamed: the remaining one will be called 'refcnt' in both mbuf and
> > mbuf_ext_shared_info.
Does this need a deprecation notice in 20.08?

> 
> Got it. I agree with you.
> It should work. In my local test machine, the ABI checker happy with this
> approach.
> Once the test is done, I will upstream the new patch.
> 
> Appreciate your comments.
> 
> Thanks,
> Phil
Phil Yang July 9, 2020, 2:10 p.m. UTC | #4
<snip>

> 
> > >
> > > Hi Phil,
> > >
> > > On Thu, Jul 09, 2020 at 06:10:42PM +0800, Phil Yang wrote:
> > > > Use C11 atomic built-ins with explicit ordering instead of
> > > > rte_atomic ops which enforce unnecessary barriers on aarch64.
> > > >
> > > > Signed-off-by: Phil Yang <phil.yang@arm.com>
> > > > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > > > ---
> > > > v3:
> > > > 1.Fix ABI breakage.
> > > > 2.Simplify data type cast.
> > > >
> > > > v2:
> > > > Fix ABI issue: revert the rte_mbuf_ext_shared_info struct refcnt
> > > > field to refcnt_atomic.
> > > >
> > > >  lib/librte_mbuf/rte_mbuf.c      |  1 -
> > > >  lib/librte_mbuf/rte_mbuf.h      | 19 ++++++++++---------
> > > >  lib/librte_mbuf/rte_mbuf_core.h |  2 +-
> > > >  3 files changed, 11 insertions(+), 11 deletions(-)
> > > >
> > <snip>
> > > >
> > > >  /* Reinitialize counter before mbuf freeing. */ diff --git
> > > > a/lib/librte_mbuf/rte_mbuf_core.h
> > > b/lib/librte_mbuf/rte_mbuf_core.h
> > > > index 16600f1..d65d1c8 100644
> > > > --- a/lib/librte_mbuf/rte_mbuf_core.h
> > > > +++ b/lib/librte_mbuf/rte_mbuf_core.h
> > > > @@ -679,7 +679,7 @@ typedef void
> > > (*rte_mbuf_extbuf_free_callback_t)(void *addr, void *opaque);
> > > >  struct rte_mbuf_ext_shared_info {
> > > >  rte_mbuf_extbuf_free_callback_t free_cb; /**< Free callback
> > > function */
> > > >  void *fcb_opaque;                        /**< Free callback argument */
> > > > -rte_atomic16_t refcnt_atomic;        /**< Atomically accessed refcnt */
> > > > +uint16_t refcnt_atomic;              /**< Atomically accessed refcnt */
> > > >  };
> > >
> > > To avoid an API breakage (i.e. currently, an application that accesses
> > > to refcnt_atomic expects that its type is rte_atomic16_t), I suggest
> > > to do the same than in the mbuf struct:
> > >
> > > union {
> > > rte_atomic16_t refcnt_atomic;
> > > uint16_t refcnt;
> > > };
> > >
> > > I hope the ABI checker won't complain.
> > >
> > > It will also be better for 20.11 when the deprecated fields will be
> > > renamed: the remaining one will be called 'refcnt' in both mbuf and
> > > mbuf_ext_shared_info.
> Does this need a deprecation notice in 20.08?

Yes. We'd better do that.
I will add a notice for it in this patch. Thanks.

> 
> >
> > Got it. I agree with you.
> > It should work. In my local test machine, the ABI checker happy with this
> > approach.
> > Once the test is done, I will upstream the new patch.
> >
> > Appreciate your comments.
> >
> > Thanks,
> > Phil

Patch
diff mbox series

diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
index ae91ae2..8a456e5 100644
--- a/lib/librte_mbuf/rte_mbuf.c
+++ b/lib/librte_mbuf/rte_mbuf.c
@@ -22,7 +22,6 @@ 
 #include <rte_eal.h>
 #include <rte_per_lcore.h>
 #include <rte_lcore.h>
-#include <rte_atomic.h>
 #include <rte_branch_prediction.h>
 #include <rte_mempool.h>
 #include <rte_mbuf.h>
diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index f8e492e..c1c0956 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -37,7 +37,6 @@ 
 #include <rte_config.h>
 #include <rte_mempool.h>
 #include <rte_memory.h>
-#include <rte_atomic.h>
 #include <rte_prefetch.h>
 #include <rte_branch_prediction.h>
 #include <rte_byteorder.h>
@@ -365,7 +364,7 @@  rte_pktmbuf_priv_flags(struct rte_mempool *mp)
 static inline uint16_t
 rte_mbuf_refcnt_read(const struct rte_mbuf *m)
 {
-	return (uint16_t)(rte_atomic16_read(&m->refcnt_atomic));
+	return __atomic_load_n(&m->refcnt, __ATOMIC_RELAXED);
 }
 
 /**
@@ -378,14 +377,15 @@  rte_mbuf_refcnt_read(const struct rte_mbuf *m)
 static inline void
 rte_mbuf_refcnt_set(struct rte_mbuf *m, uint16_t new_value)
 {
-	rte_atomic16_set(&m->refcnt_atomic, (int16_t)new_value);
+	__atomic_store_n(&m->refcnt, new_value, __ATOMIC_RELAXED);
 }
 
 /* internal */
 static inline uint16_t
 __rte_mbuf_refcnt_update(struct rte_mbuf *m, int16_t value)
 {
-	return (uint16_t)(rte_atomic16_add_return(&m->refcnt_atomic, value));
+	return __atomic_add_fetch(&m->refcnt, (uint16_t)value,
+				 __ATOMIC_ACQ_REL);
 }
 
 /**
@@ -466,7 +466,7 @@  rte_mbuf_refcnt_set(struct rte_mbuf *m, uint16_t new_value)
 static inline uint16_t
 rte_mbuf_ext_refcnt_read(const struct rte_mbuf_ext_shared_info *shinfo)
 {
-	return (uint16_t)(rte_atomic16_read(&shinfo->refcnt_atomic));
+	return __atomic_load_n(&shinfo->refcnt_atomic, __ATOMIC_RELAXED);
 }
 
 /**
@@ -481,7 +481,7 @@  static inline void
 rte_mbuf_ext_refcnt_set(struct rte_mbuf_ext_shared_info *shinfo,
 	uint16_t new_value)
 {
-	rte_atomic16_set(&shinfo->refcnt_atomic, (int16_t)new_value);
+	__atomic_store_n(&shinfo->refcnt_atomic, new_value, __ATOMIC_RELAXED);
 }
 
 /**
@@ -505,7 +505,8 @@  rte_mbuf_ext_refcnt_update(struct rte_mbuf_ext_shared_info *shinfo,
 		return (uint16_t)value;
 	}
 
-	return (uint16_t)rte_atomic16_add_return(&shinfo->refcnt_atomic, value);
+	return __atomic_add_fetch(&shinfo->refcnt_atomic, (uint16_t)value,
+				 __ATOMIC_ACQ_REL);
 }
 
 /** Mbuf prefetch */
@@ -1304,8 +1305,8 @@  static inline int __rte_pktmbuf_pinned_extbuf_decref(struct rte_mbuf *m)
 	 * Direct usage of add primitive to avoid
 	 * duplication of comparing with one.
 	 */
-	if (likely(rte_atomic16_add_return
-			(&shinfo->refcnt_atomic, -1)))
+	if (likely(__atomic_add_fetch(&shinfo->refcnt_atomic, (uint16_t)-1,
+				     __ATOMIC_ACQ_REL)))
 		return 1;
 
 	/* Reinitialize counter before mbuf freeing. */
diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h
index 16600f1..d65d1c8 100644
--- a/lib/librte_mbuf/rte_mbuf_core.h
+++ b/lib/librte_mbuf/rte_mbuf_core.h
@@ -679,7 +679,7 @@  typedef void (*rte_mbuf_extbuf_free_callback_t)(void *addr, void *opaque);
 struct rte_mbuf_ext_shared_info {
 	rte_mbuf_extbuf_free_callback_t free_cb; /**< Free callback function */
 	void *fcb_opaque;                        /**< Free callback argument */
-	rte_atomic16_t refcnt_atomic;        /**< Atomically accessed refcnt */
+	uint16_t refcnt_atomic;              /**< Atomically accessed refcnt */
 };
 
 /**< Maximum number of nb_segs allowed. */