[dpdk-dev] [PATCH v11 1/3] eal/arm64: add 128-bit atomic compare exchange
Phil Yang
phil.yang at arm.com
Fri Oct 18 13:21:28 CEST 2019
This patch adds the implementation of the 128-bit atomic compare
exchange API on AArch64. Using 64-bit 'ldxp/stxp' instructions
can perform this operation. Moreover, on the LSE atomic extension
accelerated platforms, it implemented by 'casp' instructions for
better performance.
Since the '__ARM_FEATURE_ATOMICS' flag only supports GCC-9, so this
patch adds a new config flag 'RTE_ARM_FEATURE_ATOMICS' to enable the
'cas' version on elder version compilers.
Since direct x0 register used in the code and cas_op_name() and
rte_atomic128_cmp_exchange() is inline function, based on parent
function load, it may corrupt x0 register aka Break arm64 ABI.
Define CAS operations as rte_noinline functions to avoid the ABI
break[1].
[1]5b40ec6b9662 ("mempool/octeontx2: fix possible arm64 ABI break").
Suggested-by: Jerin Jacob <jerinj at marvell.com>
Signed-off-by: Phil Yang <phil.yang at arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
Tested-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
Acked-by: Jerin Jacob <jerinj at marvell.com>
---
v11:
1. Renamed cas_op_name by adding the data width tag 128.
2. Replaced __ldx/__stx inline functions with macros.
3. Illustrate the reason of define cas operations as non-inline
functions in commitlog.
v10:
1.Removed all the rte tag for internal functions.
2.Removed __MO_LOAD and _MO_STORE macros and keep define __HAS_ACQ
and __HAS_REL under non LSE conditional branch.
3.Undef the macro once it is unused.
4.Reword the 1/3 and 2/3 patches' commitlog more specific.
v9:
Updated 19.11 release note.
v8:
Fixed "WARNING:LONG_LINE: line over 80 characters" warnings with latest kernel
checkpatch.pl
v7:
1. Adjust code comment.
v6:
1. Put the RTE_ARM_FEATURE_ATOMICS flag into EAL group. (Jerin Jocob)
2. Keep rte_stack_lf_stubs.h doing nothing. (Gage Eads)
3. Fixed 32 bit build issue.
v5:
1. Enable RTE_ARM_FEATURE_ATOMICS on octeontx2 in default. (Jerin Jocob)
2. Record the reason of introducing "rte_stack_lf_stubs.h" in git
commit.
(Jerin, Jocob)
3. Fixed a conditional MACRO error in rte_atomic128_cmp_exchange. (Jerin
Jocob)
v4:
1. Add RTE_ARM_FEATURE_ATOMICS flag to support LSE CASP instructions.
(Jerin Jocob)
2. Fix possible arm64 ABI break by making casp_op_name noinline. (Jerin
Jocob)
3. Add rte_stack_lf_stubs.h to reduce the ifdef clutter. (Gage
Eads/Jerin Jocob)
v3:
1. Avoid duplication code with macro. (Jerin Jocob)
2. Make invalid memory order to strongest barrier. (Jerin Jocob)
3. Update doc/guides/prog_guide/env_abstraction_layer.rst. (Gage Eads)
4. Fix 32-bit x86 builds issue. (Gage Eads)
5. Correct documentation issues in UT. (Gage Eads)
v2:
Initial version.
config/arm/meson.build | 2 +
config/common_base | 3 +
config/defconfig_arm64-octeontx2-linuxapp-gcc | 1 +
config/defconfig_arm64-thunderx2-linuxapp-gcc | 1 +
.../common/include/arch/arm/rte_atomic_64.h | 151 +++++++++++++++++++++
.../common/include/arch/x86/rte_atomic_64.h | 12 --
lib/librte_eal/common/include/generic/rte_atomic.h | 17 ++-
7 files changed, 174 insertions(+), 13 deletions(-)
diff --git a/config/arm/meson.build b/config/arm/meson.build
index 979018e..9f28271 100644
--- a/config/arm/meson.build
+++ b/config/arm/meson.build
@@ -71,11 +71,13 @@ flags_thunderx2_extra = [
['RTE_CACHE_LINE_SIZE', 64],
['RTE_MAX_NUMA_NODES', 2],
['RTE_MAX_LCORE', 256],
+ ['RTE_ARM_FEATURE_ATOMICS', true],
['RTE_USE_C11_MEM_MODEL', true]]
flags_octeontx2_extra = [
['RTE_MACHINE', '"octeontx2"'],
['RTE_MAX_NUMA_NODES', 1],
['RTE_MAX_LCORE', 24],
+ ['RTE_ARM_FEATURE_ATOMICS', true],
['RTE_EAL_IGB_UIO', false],
['RTE_USE_C11_MEM_MODEL', true]]
diff --git a/config/common_base b/config/common_base
index e843a21..a96beb9 100644
--- a/config/common_base
+++ b/config/common_base
@@ -82,6 +82,9 @@ CONFIG_RTE_MAX_LCORE=128
CONFIG_RTE_MAX_NUMA_NODES=8
CONFIG_RTE_MAX_HEAPS=32
CONFIG_RTE_MAX_MEMSEG_LISTS=64
+
+# Use ARM LSE ATOMIC instructions
+CONFIG_RTE_ARM_FEATURE_ATOMICS=n
# each memseg list will be limited to either RTE_MAX_MEMSEG_PER_LIST pages
# or RTE_MAX_MEM_MB_PER_LIST megabytes worth of memory, whichever is smaller
CONFIG_RTE_MAX_MEMSEG_PER_LIST=8192
diff --git a/config/defconfig_arm64-octeontx2-linuxapp-gcc b/config/defconfig_arm64-octeontx2-linuxapp-gcc
index f20da24..7687dbe 100644
--- a/config/defconfig_arm64-octeontx2-linuxapp-gcc
+++ b/config/defconfig_arm64-octeontx2-linuxapp-gcc
@@ -9,6 +9,7 @@ CONFIG_RTE_MACHINE="octeontx2"
CONFIG_RTE_CACHE_LINE_SIZE=128
CONFIG_RTE_MAX_NUMA_NODES=1
CONFIG_RTE_MAX_LCORE=24
+CONFIG_RTE_ARM_FEATURE_ATOMICS=y
# Doesn't support NUMA
CONFIG_RTE_EAL_NUMA_AWARE_HUGEPAGES=n
diff --git a/config/defconfig_arm64-thunderx2-linuxapp-gcc b/config/defconfig_arm64-thunderx2-linuxapp-gcc
index cc5c64b..af4a89c 100644
--- a/config/defconfig_arm64-thunderx2-linuxapp-gcc
+++ b/config/defconfig_arm64-thunderx2-linuxapp-gcc
@@ -9,3 +9,4 @@ CONFIG_RTE_MACHINE="thunderx2"
CONFIG_RTE_CACHE_LINE_SIZE=64
CONFIG_RTE_MAX_NUMA_NODES=2
CONFIG_RTE_MAX_LCORE=256
+CONFIG_RTE_ARM_FEATURE_ATOMICS=y
diff --git a/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h b/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h
index 97060e4..d9ebccc 100644
--- a/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h
+++ b/lib/librte_eal/common/include/arch/arm/rte_atomic_64.h
@@ -1,5 +1,6 @@
/* SPDX-License-Identifier: BSD-3-Clause
* Copyright(c) 2015 Cavium, Inc
+ * Copyright(c) 2019 Arm Limited
*/
#ifndef _RTE_ATOMIC_ARM64_H_
@@ -14,6 +15,9 @@ extern "C" {
#endif
#include "generic/rte_atomic.h"
+#include <rte_branch_prediction.h>
+#include <rte_compat.h>
+#include <rte_debug.h>
#define dsb(opt) asm volatile("dsb " #opt : : : "memory")
#define dmb(opt) asm volatile("dmb " #opt : : : "memory")
@@ -40,6 +44,153 @@ extern "C" {
#define rte_cio_rmb() dmb(oshld)
+/*------------------------ 128 bit atomic operations -------------------------*/
+
+#if defined(__ARM_FEATURE_ATOMICS) || defined(RTE_ARM_FEATURE_ATOMICS)
+#define __ATOMIC128_CAS_OP(cas_op_name, op_string) \
+static __rte_noinline rte_int128_t \
+cas_op_name(rte_int128_t *dst, rte_int128_t old, \
+ rte_int128_t updated) \
+{ \
+ /* caspX instructions register pair must start from even-numbered
+ * register at operand 1.
+ * So, specify registers for local variables here.
+ */ \
+ register uint64_t x0 __asm("x0") = (uint64_t)old.val[0]; \
+ register uint64_t x1 __asm("x1") = (uint64_t)old.val[1]; \
+ register uint64_t x2 __asm("x2") = (uint64_t)updated.val[0]; \
+ register uint64_t x3 __asm("x3") = (uint64_t)updated.val[1]; \
+ asm volatile( \
+ op_string " %[old0], %[old1], %[upd0], %[upd1], [%[dst]]" \
+ : [old0] "+r" (x0), \
+ [old1] "+r" (x1) \
+ : [upd0] "r" (x2), \
+ [upd1] "r" (x3), \
+ [dst] "r" (dst) \
+ : "memory"); \
+ old.val[0] = x0; \
+ old.val[1] = x1; \
+ return old; \
+}
+
+__ATOMIC128_CAS_OP(__cas_128_relaxed, "casp")
+__ATOMIC128_CAS_OP(__cas_128_acquire, "caspa")
+__ATOMIC128_CAS_OP(__cas_128_release, "caspl")
+__ATOMIC128_CAS_OP(__cas_128_acq_rel, "caspal")
+
+#undef __ATOMIC128_CAS_OP
+
+#endif
+
+__rte_experimental
+static inline int
+rte_atomic128_cmp_exchange(rte_int128_t *dst,
+ rte_int128_t *exp,
+ const rte_int128_t *src,
+ unsigned int weak,
+ int success,
+ int failure)
+{
+ /* Always do strong CAS */
+ RTE_SET_USED(weak);
+ /* Ignore memory ordering for failure, memory order for
+ * success must be stronger or equal
+ */
+ RTE_SET_USED(failure);
+ /* Find invalid memory order */
+ RTE_ASSERT(success == __ATOMIC_RELAXED
+ || success == __ATOMIC_ACQUIRE
+ || success == __ATOMIC_RELEASE
+ || success == __ATOMIC_ACQ_REL
+ || success == __ATOMIC_SEQ_CST);
+
+ rte_int128_t expected = *exp;
+ rte_int128_t desired = *src;
+ rte_int128_t old;
+
+#if defined(__ARM_FEATURE_ATOMICS) || defined(RTE_ARM_FEATURE_ATOMICS)
+ if (success == __ATOMIC_RELAXED)
+ old = __cas_128_relaxed(dst, expected, desired);
+ else if (success == __ATOMIC_ACQUIRE)
+ old = __cas_128_acquire(dst, expected, desired);
+ else if (success == __ATOMIC_RELEASE)
+ old = __cas_128_release(dst, expected, desired);
+ else
+ old = __cas_128_acq_rel(dst, expected, desired);
+#else
+#define __HAS_ACQ(mo) ((mo) != __ATOMIC_RELAXED && (mo) != __ATOMIC_RELEASE)
+#define __HAS_RLS(mo) ((mo) == __ATOMIC_RELEASE || (mo) == __ATOMIC_ACQ_REL || \
+ (mo) == __ATOMIC_SEQ_CST)
+
+ int ldx_mo = __HAS_ACQ(success) ? __ATOMIC_ACQUIRE : __ATOMIC_RELAXED;
+ int stx_mo = __HAS_RLS(success) ? __ATOMIC_RELEASE : __ATOMIC_RELAXED;
+
+#undef __HAS_ACQ
+#undef __HAS_RLS
+
+ uint32_t ret = 1;
+
+ /* ldx128 can not guarantee atomic,
+ * Must write back src or old to verify atomicity of ldx128;
+ */
+ do {
+
+#define __LOAD_128(op_string, src, dst) {\
+ asm volatile( \
+ op_string " %0, %1, %2" \
+ : "=&r" (dst.val[0]), \
+ "=&r" (dst.val[1]) \
+ : "Q" (src->val[0]) \
+ : "memory"); }
+
+ if (ldx_mo == __ATOMIC_RELAXED)
+ __LOAD_128("ldxp", dst, old)
+ else
+ __LOAD_128("ldaxp", dst, old)
+
+#undef __LOAD_128
+
+#define __STORE_128(op_string, dst, src, ret) {\
+ asm volatile( \
+ op_string " %w0, %1, %2, %3" \
+ : "=&r" (ret) \
+ : "r" (src.val[0]), \
+ "r" (src.val[1]), \
+ "Q" (dst->val[0]) \
+ : "memory"); }
+
+ if (likely(old.int128 == expected.int128)) {
+ if (stx_mo == __ATOMIC_RELAXED)
+ __STORE_128("stxp", dst, desired, ret)
+ else
+ __STORE_128("stlxp", dst, desired, ret)
+ } else {
+ /* In the failure case (since 'weak' is ignored and only
+ * weak == 0 is implemented), expected should contain
+ * the atomically read value of dst. This means, 'old'
+ * needs to be stored back to ensure it was read
+ * atomically.
+ */
+ if (stx_mo == __ATOMIC_RELAXED)
+ __STORE_128("stxp", dst, old, ret)
+ else
+ __STORE_128("stlxp", dst, old, ret)
+ }
+#undef __STORE_128
+
+ } while (unlikely(ret));
+#endif
+
+ /* Unconditionally updating expected removes
+ * an 'if' statement.
+ * expected should already be in register if
+ * not in the cache.
+ */
+ *exp = old;
+
+ return (old.int128 == expected.int128);
+}
+
#ifdef __cplusplus
}
#endif
diff --git a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
index 1335d92..cfe7067 100644
--- a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
+++ b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
@@ -183,18 +183,6 @@ static inline void rte_atomic64_clear(rte_atomic64_t *v)
/*------------------------ 128 bit atomic operations -------------------------*/
-/**
- * 128-bit integer structure.
- */
-RTE_STD_C11
-typedef struct {
- RTE_STD_C11
- union {
- uint64_t val[2];
- __extension__ __int128 int128;
- };
-} __rte_aligned(16) rte_int128_t;
-
__rte_experimental
static inline int
rte_atomic128_cmp_exchange(rte_int128_t *dst,
diff --git a/lib/librte_eal/common/include/generic/rte_atomic.h b/lib/librte_eal/common/include/generic/rte_atomic.h
index 24ff7dc..e6ab15a 100644
--- a/lib/librte_eal/common/include/generic/rte_atomic.h
+++ b/lib/librte_eal/common/include/generic/rte_atomic.h
@@ -1081,6 +1081,20 @@ static inline void rte_atomic64_clear(rte_atomic64_t *v)
/*------------------------ 128 bit atomic operations -------------------------*/
+/**
+ * 128-bit integer structure.
+ */
+RTE_STD_C11
+typedef struct {
+ RTE_STD_C11
+ union {
+ uint64_t val[2];
+#ifdef RTE_ARCH_64
+ __extension__ __int128 int128;
+#endif
+ };
+} __rte_aligned(16) rte_int128_t;
+
#ifdef __DOXYGEN__
/**
@@ -1093,7 +1107,8 @@ static inline void rte_atomic64_clear(rte_atomic64_t *v)
* *exp = *dst
* @endcode
*
- * @note This function is currently only available for the x86-64 platform.
+ * @note This function is currently available for the x86-64 and aarch64
+ * platforms.
*
* @note The success and failure arguments must be one of the __ATOMIC_* values
* defined in the C++11 standard. For details on their behavior, refer to the
--
2.7.4
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