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authorFerruh Yigit <ferruh.yigit@intel.com>2019-01-14 15:49:35 +0000
committerThomas Monjalon <thomas@monjalon.net>2019-01-14 17:27:48 +0100
commita32ca9a4ebc1350ce48df0222decef95a72b742b (patch)
treedba4242ba996025414bf1935a66a4e1a49f11552
parentbf78d4dc2ba64e69fda4cc569f99cfb4c806474a (diff)
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mk: fix scope of disabling AVX512F support
AVX512 was disabled for GCC because of Bugzilla issue 97 [1], the GCC defect submitted for the issue [2] highlighted that this is a known binutils version 2.30 issue. Narrowed the scope of no-avx512 to the this specific binutils version. [1] https://bugs.dpdk.org/show_bug.cgi?id=97 [2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88096 Fixes: 8d07c82b239f ("mk: disable gcc AVX512F support") Cc: stable@dpdk.org Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com> Acked-by: Thomas Monjalon <thomas@monjalon.net>
-rw-r--r--config/meson.build8
-rw-r--r--doc/guides/rel_notes/known_issues.rst35
-rw-r--r--doc/guides/rel_notes/release_19_02.rst15
-rw-r--r--mk/rte.cpuflags.mk4
-rw-r--r--mk/toolchain/gcc/rte.toolchain-compat.mk10
5 files changed, 70 insertions, 2 deletions
diff --git a/config/meson.build b/config/meson.build
index db32499..40802fc 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -43,6 +43,14 @@ toolchain = cc.get_id()
dpdk_conf.set_quoted('RTE_TOOLCHAIN', toolchain)
dpdk_conf.set('RTE_TOOLCHAIN_' + toolchain.to_upper(), 1)
+# get binutils version for the workaround of Bug 97
+ldver = run_command('ld', '-v').stdout().strip()
+if ldver.contains('2.30')
+ if cc.has_argument('-mno-avx512f')
+ machine_args += '-mno-avx512f'
+ endif
+endif
+
add_project_link_arguments('-Wl,--no-as-needed', language: 'c')
dpdk_extra_ldflags += '-Wl,--no-as-needed'
diff --git a/doc/guides/rel_notes/known_issues.rst b/doc/guides/rel_notes/known_issues.rst
index a1face9..358dfa3 100644
--- a/doc/guides/rel_notes/known_issues.rst
+++ b/doc/guides/rel_notes/known_issues.rst
@@ -826,3 +826,38 @@ Kernel crash when hot-unplug igb_uio device while DPDK application is running
**Driver/Module**:
``igb_uio`` module.
+
+
+AVX-512 support disabled
+------------------------
+
+**Description**:
+ ``AVX-512`` support has been disabled on some conditions.
+ This shouldn't be confused with ``CONFIG_RTE_ENABLE_AVX512`` config option which is already
+ disabled by default. This config option defines if ``AVX-512`` specific implementations of
+ some file to be used or not. What has been disabled is compiler feature to produce ``AVX-512``
+ instructions from any source code.
+
+ On DPDK v18.11 ``AVX-512`` is disabled for all ``GCC`` builds which reported to cause a performance
+ drop.
+
+ On DPDK v19.02 ``AVX-512`` disable scope is reduced to ``GCC`` and ``binutils version 2.30`` based
+ on information accured from the GCC community defect.
+
+**Reason**:
+ Generated ``AVX-512`` code cause crash:
+ https://bugs.dpdk.org/show_bug.cgi?id=97
+ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88096
+
+**Resolution/Workaround**:
+ * Update ``binutils`` to newer version than ``2.30``.
+
+ OR
+
+ * Use different compiler, like ``clang`` for this case.
+
+**Affected Environment/Platform**:
+ ``GCC`` and ``binutils version 2.30``.
+
+**Driver/Module**:
+ ALL.
diff --git a/doc/guides/rel_notes/release_19_02.rst b/doc/guides/rel_notes/release_19_02.rst
index 832ac8c..5a2f62c 100644
--- a/doc/guides/rel_notes/release_19_02.rst
+++ b/doc/guides/rel_notes/release_19_02.rst
@@ -334,6 +334,21 @@ Known Issues
Also, make sure to start the actual text at the margin.
=========================================================
+* ``AVX-512`` support has been disabled for ``GCC`` builds when ``binutils 2.30``
+ is detected [1] because of a crash [2]. This can affect ``native`` machine type
+ build targets on the platforms that support ``AVX512F`` like ``Intel Skylake``
+ processors, and can cause a possible performance drop. The immediate workaround
+ is to use ``clang`` compiler on these platforms.
+ Initial workaround in DPDK v18.11 was to disable ``AVX-512`` support for ``GCC``
+ completely, but based on information on defect submitted to GCC community [3],
+ issue has been identified as ``binutils 2.30`` issue. Since currently only GCC
+ generates ``AVX-512`` instructions, the scope is limited to ``GCC`` and
+ ``binutils 2.30``
+
+ - [1]: Commit ("mk: fix scope of disabling AVX512F support")
+ - [2]: https://bugs.dpdk.org/show_bug.cgi?id=97
+ - [3]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88096
+
Tested Platforms
----------------
diff --git a/mk/rte.cpuflags.mk b/mk/rte.cpuflags.mk
index c3291b1..541211c 100644
--- a/mk/rte.cpuflags.mk
+++ b/mk/rte.cpuflags.mk
@@ -69,8 +69,8 @@ ifneq ($(filter $(AUTO_CPUFLAGS),__AVX512F__),)
ifeq ($(CONFIG_RTE_ENABLE_AVX512),y)
CPUFLAGS += AVX512F
else
-# disable AVX512F support of gcc as a workaround for Bug 97
-ifeq ($(CONFIG_RTE_TOOLCHAIN_GCC),y)
+# disable AVX512F support for GCC & binutils 2.30 as a workaround for Bug 97
+ifeq ($(FORCE_DISABLE_AVX512),y)
MACHINE_CFLAGS += -mno-avx512f
endif
endif
diff --git a/mk/toolchain/gcc/rte.toolchain-compat.mk b/mk/toolchain/gcc/rte.toolchain-compat.mk
index 4490429..dbddc98 100644
--- a/mk/toolchain/gcc/rte.toolchain-compat.mk
+++ b/mk/toolchain/gcc/rte.toolchain-compat.mk
@@ -20,6 +20,16 @@ HOST_GCC_MINOR = $(shell echo __GNUC_MINOR__ | $(HOSTCC) -E -x c - | tail -n 1)
HOST_GCC_PATCHLEVEL = $(shell echo __GNUC_PATCHLEVEL__ | $(HOSTCC) -E -x c - | tail -n 1)
HOST_GCC_VERSION = $(HOST_GCC_MAJOR)$(HOST_GCC_MINOR)
+LD_VERSION = $(shell $(LD) -v)
+# disable AVX512F support for GCC & binutils 2.30 as a workaround for Bug 97
+ifneq ($(filter 2.30%,$(LD_VERSION)),)
+FORCE_DISABLE_AVX512 := y
+# print warning only once for librte_eal
+ifneq ($(filter %librte_eal,$(CURDIR)),)
+$(warning AVX512 support disabled because of ld 2.30. See Bug 97)
+endif
+endif
+
# if GCC is older than 4.x
ifeq ($(shell test $(GCC_VERSION) -lt 40 && echo 1), 1)
MACHINE_CFLAGS =