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Subject: [dpdk-dev] [Bug 97] rte_memcpy() moves data incorrectly on Ubuntu
18.04 on Intel Skylake
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https://bugs.dpdk.org/show_bug.cgi?id=3D97
Bug ID: 97
Summary: rte_memcpy() moves data incorrectly on Ubuntu 18.04 on
Intel Skylake
Product: DPDK
Version: 18.08
Hardware: x86
OS: Linux
Status: CONFIRMED
Severity: critical
Priority: Normal
Component: core
Assignee: dev@dpdk.org
Reporter: yskoh@mellanox.com
Target Milestone: ---
Reported by:
https://mails.dpdk.org/archives/dev/2018-September/111522.html
We've recently encountered a weird issue with Ubuntu 18.04 on the Skylake
server. I can always reproduce this crash and I could narrowed it down. I g=
uess
it could be a GCC issue.
[1] How to reproduce
- ConnectX-4Lx/ConnectX-5 with mlx5 PMD in DPDK 18.02/18.05/18.08
- Ubuntu 18.04 on Intel Skylake server
- gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
- Testpmd crashes when it starts to forward traffic. Easy to reproduce.
- Only happens on the Skylake server.
[2] Failure point
The attached patch gives an insight of why it crashes. The following is the
result of the patch and the GDB commands.
In summary, rte_memcpy() doesn't work as expected. In __mempool_generic_put=
(),
there's rte_memcpy() to move the array of objects to the lcore cache. If I =
run
memcmp() right after rte_memcpy(dst, src, n), data in dst differs from data=
in
src. And it looks like some of data got shifted by a few bytes as you can s=
ee
below.
[GDB command]
$dst =3D 0x7ffff4e09ea8
$src =3D 0x7fffce3fb970
$n =3D 256
x/32gx 0x7ffff4e09ea8
x/32gx 0x7fffce3fb970
testpmd: /home/mlnxtest/dpdk/build/include/rte_mempool.h:1140:
__mempool_generic_put: Assertion `0' failed.
Thread 4 "lcore-slave-1" received signal SIGABRT, Aborted.
[Switching to Thread 0x7fffce3ff700 (LWP 69913)]
(gdb) x/32gx 0x7ffff4e09ea8
0x7ffff4e09ea8: 0x00007fffaac38ec0 0x00007fffaac38500
0x7ffff4e09eb8: 0x00007fffaac37b40 0x00007fffaac37180
0x7ffff4e09ec8: 0x850000007fffaac3 0x7b4000007fffaac3
0x7ffff4e09ed8: 0x00007fffaac35440 0x00007fffaac34a80
0x7ffff4e09ee8: 0xaac3850000007fff 0xaac37b4000007fff
0x7ffff4e09ef8: 0x00007fffaac32d40 0x00007fffaac32380
0x7ffff4e09f08: 0x7fffaac385000000 0x7fffaac37b400000
0x7ffff4e09f18: 0x00007fffaac30640 0x00007fffaac2fc80
0x7ffff4e09f28: 0x00007fffaac2f2c0 0x00007fffaac2e900
0x7ffff4e09f38: 0x00007fffaac2df40 0x00007fffaac2d580
0x7ffff4e09f48: 0x00007fffaac2cbc0 0x00007fffaac2c200
0x7ffff4e09f58: 0x00007fffaac2b840 0x00007fffaac2ae80
0x7ffff4e09f68: 0x00007fffaac2a4c0 0x00007fffaac29b00
0x7ffff4e09f78: 0x00007fffaac29140 0x00007fffaac28780
0x7ffff4e09f88: 0x00007fffaac27dc0 0x00007fffaac27400
0x7ffff4e09f98: 0x00007fffaac26a40 0x00007fffaac26080
(gdb) x/32gx 0x7fffce3fb970
0x7fffce3fb970: 0x00007fffaac38ec0 0x00007fffaac38500
0x7fffce3fb980: 0x00007fffaac37b40 0x00007fffaac37180
0x7fffce3fb990: 0x00007fffaac367c0 0x00007fffaac35e00
0x7fffce3fb9a0: 0x00007fffaac35440 0x00007fffaac34a80
0x7fffce3fb9b0: 0x00007fffaac340c0 0x00007fffaac33700
0x7fffce3fb9c0: 0x00007fffaac32d40 0x00007fffaac32380
0x7fffce3fb9d0: 0x00007fffaac319c0 0x00007fffaac31000
0x7fffce3fb9e0: 0x00007fffaac30640 0x00007fffaac2fc80
0x7fffce3fb9f0: 0x00007fffaac2f2c0 0x00007fffaac2e900
0x7fffce3fba00: 0x00007fffaac2df40 0x00007fffaac2d580
0x7fffce3fba10: 0x00007fffaac2cbc0 0x00007fffaac2c200
0x7fffce3fba20: 0x00007fffaac2b840 0x00007fffaac2ae80
0x7fffce3fba30: 0x00007fffaac2a4c0 0x00007fffaac29b00
0x7fffce3fba40: 0x00007fffaac29140 0x00007fffaac28780
0x7fffce3fba50: 0x00007fffaac27dc0 0x00007fffaac27400
0x7fffce3fba60: 0x00007fffaac26a40 0x00007fffaac26080
AFAIK, AVX512F support is disabled by default in DPDK as it is still
experimental (CONFIG_RTE_ENABLE_AVX512=3Dn). But with gcc optimization, AVX2
version of rte_memcpy() seems to be optimized with 512b instructions. If I
disable it by adding EXTRA_CFLAGS=3D"-mno-avx512f", then it works fine and
doesn't
crash.
Do you have any idea regarding this issue or are you already aware of it?
Thanks,
Yongseok
$ git diff
diff --git a/config/common_base b/config/common_base
index ad03cf433..f512b5a88 100644
--- a/config/common_base
+++ b/config/common_base
@@ -275,8 +275,8 @@ CONFIG_RTE_LIBRTE_MLX4_TX_MP_CACHE=3D8
#
# Compile burst-oriented Mellanox ConnectX-4 & ConnectX-5 (MLX5) PMD
#
-CONFIG_RTE_LIBRTE_MLX5_PMD=3Dn
-CONFIG_RTE_LIBRTE_MLX5_DEBUG=3Dn
+CONFIG_RTE_LIBRTE_MLX5_PMD=3Dy
+CONFIG_RTE_LIBRTE_MLX5_DEBUG=3Dy
CONFIG_RTE_LIBRTE_MLX5_DLOPEN_DEPS=3Dn
CONFIG_RTE_LIBRTE_MLX5_TX_MP_CACHE=3D8
@@ -597,7 +597,7 @@ CONFIG_RTE_RING_USE_C11_MEM_MODEL=3Dn
#
CONFIG_RTE_LIBRTE_MEMPOOL=3Dy
CONFIG_RTE_MEMPOOL_CACHE_MAX_SIZE=3D512
-CONFIG_RTE_LIBRTE_MEMPOOL_DEBUG=3Dn
+CONFIG_RTE_LIBRTE_MEMPOOL_DEBUG=3Dy
#
# Compile Mempool drivers
diff --git a/lib/librte_mempool/rte_mempool.h
b/lib/librte_mempool/rte_mempool.h
index 8b1b7f7ed..9f48028d9 100644
--- a/lib/librte_mempool/rte_mempool.h
+++ b/lib/librte_mempool/rte_mempool.h
@@ -39,6 +39,7 @@
#include <errno.h>
#include <inttypes.h>
#include <sys/queue.h>
+#include <assert.h>
#include <rte_config.h>
#include <rte_spinlock.h>
@@ -1123,6 +1124,22 @@ __mempool_generic_put(struct rte_mempool *mp, void *
const *obj_table,
/* Add elements back into the cache */
rte_memcpy(&cache_objs[0], obj_table, sizeof(void *) * n);
+ if(memcmp(&cache_objs[0], obj_table, sizeof(void *) * n)) {
+ printf("[GDB command] \n"
+ "$dst =3D %p\n"
+ "$src =3D %p\n"
+ "$n =3D %ld\n"
+ "x/%ldgx %p\n"
+ "x/%ldgx %p\n",
+ (void *)&cache_objs[0],
+ (const void *)obj_table,
+ sizeof(void *) * n,
+ sizeof(void *) * n / 8, (void *)&cache_objs[0],
+ sizeof(void *) * n / 8, (const void *)obj_table
+ );
+ assert(0);
+ }
+
cache->len +=3D n;
if (cache->len >=3D cache->flushthresh) {
--=20
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