[dpdk-dev] [PATCH] mk: using initial-exec model for thread local variable

[Marvin Liu <yong.liu@intel.com>]

When building share library, thread-local storage model will be changed
to global-dynamic. It will add additional cost for reading thread local
variable. On the other hand, dynamically load share library with static
TLS will request additional DTV slot which is limited by loader. By now
only librte_pmd_eal.so contain thread local variable. So that can make
TLS model back to initial-exec like static library for better
performance.

Signed-off-by: Marvin Liu <yong.liu@intel.com>

diff --git a/mk/toolchain/gcc/rte.vars.mk b/mk/toolchain/gcc/rte.vars.mk
index 7e4531bab..19d5e11ef 100644
--- a/mk/toolchain/gcc/rte.vars.mk
+++ b/mk/toolchain/gcc/rte.vars.mk
@@ -43,6 +43,13 @@ ifeq (,$(findstring -O0,$(EXTRA_CFLAGS)))
 endif
 endif
 
+# Initial execution TLS model has better performane compared to dynamic
+# global. But this model require for addtional slot on DTV when dlopen
+# object with thread local variable.
+ifeq ($(CONFIG_RTE_BUILD_SHARED_LIB),y)
+TOOLCHAIN_CFLAGS += -ftls-model=initial-exec
+endif
+
 WERROR_FLAGS := -W -Wall -Wstrict-prototypes -Wmissing-prototypes
 WERROR_FLAGS += -Wmissing-declarations -Wold-style-definition -Wpointer-arith
 WERROR_FLAGS += -Wcast-align -Wnested-externs -Wcast-qual
-- 
2.17.0