> On July 16, 2015 at 9:23 PM Joe Perches <j...@perches.com> wrote: > > It might be useful to have these performance impacting > changes guarded by something like CONFIG_CC_OPTIMIZE_FOR_SIZE > with another static __always_inline __<func> and a function & > EXPORT_SYMBOL or just a static inline so that where code size > is critical it's uninlined.
But keep in mind that jhash, jhash2 and __jhash_nwords are *not* one-instruction long functions. We duplicate code over and over resulting probably in more cache misses. __always_inline__ is probably too strict and a vanilla inline is already for 99% of all distribution builds a __always_inline__, see ARCH_SUPPORTS_OPTIMIZED_INLINING and CONFIG_CC_OPTIMIZE_FOR_SIZE. The answer depends on the specific workload. Sometimes an enforced inline perform better and sometimes a call is the better solution (read: less cache misses). General purpose vendors with a larger working set size should reduce cache misses by deinline many functions. For high-performance special fast-path operations a strong inlined kernel build is probably faster. __always_inline__ makes it impossible for the user to deinline functions or not. Hagen -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
