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

[Thomas Monjalon <thomas@monjalon.net>]

05/07/2018 16:13, Marvin Liu:
> 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

It is only for GCC? not clang?

> +# 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.

Few typos in this comment.

> +ifeq ($(CONFIG_RTE_BUILD_SHARED_LIB),y)
> +TOOLCHAIN_CFLAGS += -ftls-model=initial-exec
> +endif

We really need more test or review of this patch.

Cc techboard: do we take the risk of getting it in RC1
without review? It is waiting for long.