On Thu, Aug 23, 2018 at 05:15:39PM -0700, Dave Hansen wrote: >On 08/23/2018 06:07 AM, Wei Yang wrote: >> And it is known, __highest_present_section_nr is a more strict boundary >> than NR_MEM_SECTIONS. > >What is the benefit of this patch? > The original idea is simple: with a more strict boundary, it will has less computation. >You're adding a more "strict" boundary, but you're also adding a >potential cacheline miss and removing optimizations that the compiler >can make with a constant vs. a variable. Providing absolute bounds >limits that the compiler knows about can actually be pretty handy for it >to optimize things You are right. I haven't thought about the compiler optimization case. > >Do you have *any* analysis to show that this has a benefit? What does >it do to text size, for instance? I don't have more analysis about this. Originally, I thought a strict boundary will have a benefit. But as you mentioned, it loose the compiler optimization. BTW, I did some tests and found during a normal boot, all the section number are within NR_MEM_SECTIONS. I am wondering in which case, this check will be valid and return 0? -- Wei Yang Help you, Help me
