[v4,1/3] rwlock: reimplement with atomic builtins

Message ID 1553063109-57574-2-git-send-email-joyce.kong@arm.com
State Superseded, archived
Delegated to: Thomas Monjalon
Headers show
Series
  • rwlock: reimplement rwlock with atomic and add relevant perf test case
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Checks

Context Check Description
ci/checkpatch success coding style OK
ci/mellanox-Performance-Testing success Performance Testing PASS
ci/intel-Performance-Testing success Performance Testing PASS
ci/Intel-compilation success Compilation OK

Commit Message

Joyce Kong March 20, 2019, 6:25 a.m.
The __sync builtin based implementation generates full memory
barriers ('dmb ish') on Arm platforms. Using C11 atomic builtins
to generate one way barriers.

Here is the assembly code of __sync_compare_and_swap builtin.
__sync_bool_compare_and_swap(dst, exp, src);
   0x000000000090f1b0 <+16>:    e0 07 40 f9 ldr x0, [sp, #8]
   0x000000000090f1b4 <+20>:    e1 0f 40 79 ldrh    w1, [sp, #6]
   0x000000000090f1b8 <+24>:    e2 0b 40 79 ldrh    w2, [sp, #4]
   0x000000000090f1bc <+28>:    21 3c 00 12 and w1, w1, #0xffff
   0x000000000090f1c0 <+32>:    03 7c 5f 48 ldxrh   w3, [x0]
   0x000000000090f1c4 <+36>:    7f 00 01 6b cmp w3, w1
   0x000000000090f1c8 <+40>:    61 00 00 54 b.ne    0x90f1d4
<rte_atomic16_cmpset+52>  // b.any
   0x000000000090f1cc <+44>:    02 fc 04 48 stlxrh  w4, w2, [x0]
   0x000000000090f1d0 <+48>:    84 ff ff 35 cbnz    w4, 0x90f1c0
<rte_atomic16_cmpset+32>
   0x000000000090f1d4 <+52>:    bf 3b 03 d5 dmb ish
   0x000000000090f1d8 <+56>:    e0 17 9f 1a cset    w0, eq  // eq = none

Signed-off-by: Gavin Hu <gavin.hu@arm.com>
Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Tested-by: Joyce Kong <joyce.kong@arm.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>
---
 lib/librte_eal/common/include/generic/rte_rwlock.h | 29 +++++++++++-----------
 1 file changed, 15 insertions(+), 14 deletions(-)

Comments

Ananyev, Konstantin March 21, 2019, 6:43 p.m. | #1
> -----Original Message-----
> From: Joyce Kong [mailto:joyce.kong@arm.com]
> Sent: Wednesday, March 20, 2019 6:25 AM
> To: dev@dpdk.org
> Cc: nd@arm.com; jerinj@marvell.com; Ananyev, Konstantin <konstantin.ananyev@intel.com>; chaozhu@linux.vnet.ibm.com; Richardson,
> Bruce <bruce.richardson@intel.com>; thomas@monjalon.net; hemant.agrawal@nxp.com; honnappa.nagarahalli@arm.com;
> gavin.hu@arm.com
> Subject: [PATCH v4 1/3] rwlock: reimplement with atomic builtins
> 
> The __sync builtin based implementation generates full memory
> barriers ('dmb ish') on Arm platforms. Using C11 atomic builtins
> to generate one way barriers.
> 
> Here is the assembly code of __sync_compare_and_swap builtin.
> __sync_bool_compare_and_swap(dst, exp, src);
>    0x000000000090f1b0 <+16>:    e0 07 40 f9 ldr x0, [sp, #8]
>    0x000000000090f1b4 <+20>:    e1 0f 40 79 ldrh    w1, [sp, #6]
>    0x000000000090f1b8 <+24>:    e2 0b 40 79 ldrh    w2, [sp, #4]
>    0x000000000090f1bc <+28>:    21 3c 00 12 and w1, w1, #0xffff
>    0x000000000090f1c0 <+32>:    03 7c 5f 48 ldxrh   w3, [x0]
>    0x000000000090f1c4 <+36>:    7f 00 01 6b cmp w3, w1
>    0x000000000090f1c8 <+40>:    61 00 00 54 b.ne    0x90f1d4
> <rte_atomic16_cmpset+52>  // b.any
>    0x000000000090f1cc <+44>:    02 fc 04 48 stlxrh  w4, w2, [x0]
>    0x000000000090f1d0 <+48>:    84 ff ff 35 cbnz    w4, 0x90f1c0
> <rte_atomic16_cmpset+32>
>    0x000000000090f1d4 <+52>:    bf 3b 03 d5 dmb ish
>    0x000000000090f1d8 <+56>:    e0 17 9f 1a cset    w0, eq  // eq = none
> 
> Signed-off-by: Gavin Hu <gavin.hu@arm.com>
> Signed-off-by: Joyce Kong <joyce.kong@arm.com>
> Tested-by: Joyce Kong <joyce.kong@arm.com>
> Acked-by: Jerin Jacob <jerinj@marvell.com>
> ---
>  lib/librte_eal/common/include/generic/rte_rwlock.h | 29 +++++++++++-----------
>  1 file changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h b/lib/librte_eal/common/include/generic/rte_rwlock.h
> index b05d85a..de94ca9 100644
> --- a/lib/librte_eal/common/include/generic/rte_rwlock.h
> +++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
> @@ -64,14 +64,14 @@ rte_rwlock_read_lock(rte_rwlock_t *rwl)
>  	int success = 0;
> 
>  	while (success == 0) {
> -		x = rwl->cnt;
> +		x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
>  		/* write lock is held */
>  		if (x < 0) {
>  			rte_pause();
>  			continue;
>  		}
> -		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
> -					      (uint32_t)x, (uint32_t)(x + 1));
> +		success = __atomic_compare_exchange_n(&rwl->cnt, &x, x+1, 1,

As a nit, here and in trylock: 'x+1' spaces missing, needs to be 'x + 1'.
Apart from that:
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Joyce Kong March 25, 2019, 9:18 a.m. | #2
Hi Konstantin,

> -----Original Message-----
> From: Ananyev, Konstantin <konstantin.ananyev@intel.com>
> Sent: Friday, March 22, 2019 2:43 AM
> To: Joyce Kong (Arm Technology China) <Joyce.Kong@arm.com>;
> dev@dpdk.org
> Cc: nd <nd@arm.com>; jerinj@marvell.com; chaozhu@linux.vnet.ibm.com;
> Richardson, Bruce <bruce.richardson@intel.com>; thomas@monjalon.net;
> hemant.agrawal@nxp.com; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; Gavin Hu (Arm Technology China)
> <Gavin.Hu@arm.com>
> Subject: RE: [PATCH v4 1/3] rwlock: reimplement with atomic builtins
> 
> 
> 
> > -----Original Message-----
> > From: Joyce Kong [mailto:joyce.kong@arm.com]
> > Sent: Wednesday, March 20, 2019 6:25 AM
> > To: dev@dpdk.org
> > Cc: nd@arm.com; jerinj@marvell.com; Ananyev, Konstantin
> > <konstantin.ananyev@intel.com>; chaozhu@linux.vnet.ibm.com;
> > Richardson, Bruce <bruce.richardson@intel.com>; thomas@monjalon.net;
> > hemant.agrawal@nxp.com; honnappa.nagarahalli@arm.com;
> gavin.hu@arm.com
> > Subject: [PATCH v4 1/3] rwlock: reimplement with atomic builtins
> >
> > The __sync builtin based implementation generates full memory barriers
> > ('dmb ish') on Arm platforms. Using C11 atomic builtins to generate
> > one way barriers.
> >
> > Here is the assembly code of __sync_compare_and_swap builtin.
> > __sync_bool_compare_and_swap(dst, exp, src);
> >    0x000000000090f1b0 <+16>:    e0 07 40 f9 ldr x0, [sp, #8]
> >    0x000000000090f1b4 <+20>:    e1 0f 40 79 ldrh    w1, [sp, #6]
> >    0x000000000090f1b8 <+24>:    e2 0b 40 79 ldrh    w2, [sp, #4]
> >    0x000000000090f1bc <+28>:    21 3c 00 12 and w1, w1, #0xffff
> >    0x000000000090f1c0 <+32>:    03 7c 5f 48 ldxrh   w3, [x0]
> >    0x000000000090f1c4 <+36>:    7f 00 01 6b cmp w3, w1
> >    0x000000000090f1c8 <+40>:    61 00 00 54 b.ne    0x90f1d4
> > <rte_atomic16_cmpset+52>  // b.any
> >    0x000000000090f1cc <+44>:    02 fc 04 48 stlxrh  w4, w2, [x0]
> >    0x000000000090f1d0 <+48>:    84 ff ff 35 cbnz    w4, 0x90f1c0
> > <rte_atomic16_cmpset+32>
> >    0x000000000090f1d4 <+52>:    bf 3b 03 d5 dmb ish
> >    0x000000000090f1d8 <+56>:    e0 17 9f 1a cset    w0, eq  // eq = none
> >
> > Signed-off-by: Gavin Hu <gavin.hu@arm.com>
> > Signed-off-by: Joyce Kong <joyce.kong@arm.com>
> > Tested-by: Joyce Kong <joyce.kong@arm.com>
> > Acked-by: Jerin Jacob <jerinj@marvell.com>
> > ---
> >  lib/librte_eal/common/include/generic/rte_rwlock.h | 29
> > +++++++++++-----------
> >  1 file changed, 15 insertions(+), 14 deletions(-)
> >
> > diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h
> > b/lib/librte_eal/common/include/generic/rte_rwlock.h
> > index b05d85a..de94ca9 100644
> > --- a/lib/librte_eal/common/include/generic/rte_rwlock.h
> > +++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
> > @@ -64,14 +64,14 @@ rte_rwlock_read_lock(rte_rwlock_t *rwl)
> >  	int success = 0;
> >
> >  	while (success == 0) {
> > -		x = rwl->cnt;
> > +		x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
> >  		/* write lock is held */
> >  		if (x < 0) {
> >  			rte_pause();
> >  			continue;
> >  		}
> > -		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
> > -					      (uint32_t)x, (uint32_t)(x + 1));
> > +		success = __atomic_compare_exchange_n(&rwl->cnt, &x, x+1,
> 1,
> 
> As a nit, here and in trylock: 'x+1' spaces missing, needs to be 'x + 1'.

Change to 'x + 1' in v5.

> Apart from that:
> Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
>

Patch

diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h b/lib/librte_eal/common/include/generic/rte_rwlock.h
index b05d85a..de94ca9 100644
--- a/lib/librte_eal/common/include/generic/rte_rwlock.h
+++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
@@ -64,14 +64,14 @@  rte_rwlock_read_lock(rte_rwlock_t *rwl)
 	int success = 0;
 
 	while (success == 0) {
-		x = rwl->cnt;
+		x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
 		/* write lock is held */
 		if (x < 0) {
 			rte_pause();
 			continue;
 		}
-		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-					      (uint32_t)x, (uint32_t)(x + 1));
+		success = __atomic_compare_exchange_n(&rwl->cnt, &x, x+1, 1,
+					__ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
 	}
 }
 
@@ -95,13 +95,14 @@  rte_rwlock_read_trylock(rte_rwlock_t *rwl)
 	int success = 0;
 
 	while (success == 0) {
-		x = rwl->cnt;
+		x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
 		/* write lock is held */
 		if (x < 0)
 			return -EBUSY;
-		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-					      (uint32_t)x, (uint32_t)(x + 1));
+		success = __atomic_compare_exchange_n(&rwl->cnt, &x, x+1, 1,
+					__ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
 	}
+
 	return 0;
 }
 
@@ -114,7 +115,7 @@  rte_rwlock_read_trylock(rte_rwlock_t *rwl)
 static inline void
 rte_rwlock_read_unlock(rte_rwlock_t *rwl)
 {
-	rte_atomic32_dec((rte_atomic32_t *)(intptr_t)&rwl->cnt);
+	__atomic_fetch_sub(&rwl->cnt, 1, __ATOMIC_RELEASE);
 }
 
 /**
@@ -135,9 +136,9 @@  rte_rwlock_write_trylock(rte_rwlock_t *rwl)
 {
 	int32_t x;
 
-	x = rwl->cnt;
-	if (x != 0 || rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-				0, (uint32_t)-1) == 0)
+	x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
+	if (x != 0 || __atomic_compare_exchange_n(&rwl->cnt, &x, -1, 1,
+			      __ATOMIC_ACQUIRE, __ATOMIC_RELAXED) == 0)
 		return -EBUSY;
 
 	return 0;
@@ -156,14 +157,14 @@  rte_rwlock_write_lock(rte_rwlock_t *rwl)
 	int success = 0;
 
 	while (success == 0) {
-		x = rwl->cnt;
+		x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
 		/* a lock is held */
 		if (x != 0) {
 			rte_pause();
 			continue;
 		}
-		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-					      0, (uint32_t)-1);
+		success = __atomic_compare_exchange_n(&rwl->cnt, &x, -1, 1,
+					__ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
 	}
 }
 
@@ -176,7 +177,7 @@  rte_rwlock_write_lock(rte_rwlock_t *rwl)
 static inline void
 rte_rwlock_write_unlock(rte_rwlock_t *rwl)
 {
-	rte_atomic32_inc((rte_atomic32_t *)(intptr_t)&rwl->cnt);
+	__atomic_store_n(&rwl->cnt, 0, __ATOMIC_RELEASE);
 }
 
 /**