[v4] mk: fix scope of disabling AVX512F support
Checks
Commit Message
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>
---
Cc: Tom Barbette <barbette@kth.se>
Cc: Thomas Monjalon <thomas@monjalon.net>
Cc: Yongseok Koh <yskoh@mellanox.com>
Cc: Konstantin Ananyev <konstantin.ananyev@intel.com>
Cc: Bruce Richardson <bruce.richardson@intel.com>
v2:
* Added warning message (print only once for eal)
* Moved decision details to compat file, kept execution in cpuflags
v3:
* replace 'ld' with '$(LD)' for cross build
* added meson support
v4:
* Document this limitation in release notes
Cc: Vipin Varghese <vipin.varghese@intel.com>
---
config/meson.build | 8 ++++++
doc/guides/rel_notes/known_issues.rst | 32 ++++++++++++++++++++++++
doc/guides/rel_notes/release_19_02.rst | 13 ++++++++++
mk/rte.cpuflags.mk | 4 +--
mk/toolchain/gcc/rte.toolchain-compat.mk | 10 ++++++++
5 files changed, 65 insertions(+), 2 deletions(-)
Comments
diff --git a/doc/guides/rel_notes/known_issues.rst b/doc/guides/rel_notes/known_issues.rst
index a1face9c1..b0057a2bc 100644
--- a/doc/guides/rel_notes/known_issues.rst
+++ b/doc/guides/rel_notes/known_issues.rst
@@ -826,3 +826,35 @@ 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`` disabled for all ``GCC`` builds which reported to cause a performance
+ drop.
+
+ On DPDK v19.02 ``AVX-512`` disable scope 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``.
+ 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 39c6ff826..b6322b282 100644
--- a/doc/guides/rel_notes/release_19_02.rst
+++ b/doc/guides/rel_notes/release_19_02.rst
@@ -276,6 +276,19 @@ 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, scope 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
Sharing ACK for documentation and update in release notes
Acked-by: Vipin Varghese <Vipin.varghese@intel.com>
Hi,
Few details reviewed below,
07/01/2019 17:49, Ferruh Yigit:
> --- a/doc/guides/rel_notes/known_issues.rst
> +++ b/doc/guides/rel_notes/known_issues.rst
> +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`` disabled for all ``GCC`` builds which reported to cause a performance
> + drop.
*is* disabled
> +
> + On DPDK v19.02 ``AVX-512`` disable scope reduced to ``GCC`` and ``binutils version 2.30`` based
*is* reduced
> + 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``.
> + Use different compiler, like ``clang`` for this case.
These are 2 possible workarounds. Should we say "Or" ?
> +
> +**Affected Environment/Platform**:
> + ``GCC`` and ``binutils version 2.30``.
> --- a/doc/guides/rel_notes/release_19_02.rst
> +++ b/doc/guides/rel_notes/release_19_02.rst
> @@ -276,6 +276,19 @@ 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, scope limited to ``GCC`` and ``binutils 2.30``
*the* scope *is* limited
> +
> + - [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
>
Space missing here
> Tested Platforms
> ----------------
> --- a/mk/toolchain/gcc/rte.toolchain-compat.mk
> +++ b/mk/toolchain/gcc/rte.toolchain-compat.mk
> +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,$(lastword $(CURDIR))),)
Do we need lastword for CURDIR?
@@ -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'
@@ -826,3 +826,35 @@ 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`` disabled for all ``GCC`` builds which reported to cause a performance
+ drop.
+
+ On DPDK v19.02 ``AVX-512`` disable scope 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``.
+ Use different compiler, like ``clang`` for this case.
+
+**Affected Environment/Platform**:
+ ``GCC`` and ``binutils version 2.30``.
+
+**Driver/Module**:
+ ALL.
@@ -276,6 +276,19 @@ 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, scope 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
----------------
@@ -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
@@ -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,$(lastword $(CURDIR))),)
+$(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 =