stats: when hot-restart is disabled, each stat still consumes maxNameLength() bytes for the name.

[jmarantz]

Description:

When storing stats in shared memory for hot-restart, we preallocate max_stats * maxNameLength for string storage. But this means you have to make hard up-front decisions about how much memory you can spend. However if we disable hot-restart, there's no compelling reason to pad each stat, so you could just set maxNameLength pretty high. If that were fixed, we wouldn't have to tune maxNameLength so carefully.

@ambuc may wind up looking at this as he was the last one to dive into the not-hot-restart case.

[jmarantz]

More thoughts on this in light of the #3506 which forced me to look at the stats code again and realize this problem:

I think a solution to this problem that will improve the maintainability of the codebase is to remove the following methods & data from Stats::RawStatsData

• configure(options)
• configureForTestsOnly(options)
• maxNameLength()
• maxObjNameLength()
• nameSize()
• static initializeAndGetMutableMaxObjNameLength()
  and replace them all with:
• static calculateRequiredSize(size_t name_length)

In the context of a hot-restart allocation, the calculateRequiredSize will be called with options_->maxObjNameLength(). In the case of a non-hot-restart allocation, it will be called with actual_name.size(). Then you can remove a whole bunch of hacks in the test dealing with the static underneath initializeAndGetMutableMaxObjNameLength.

[mattklein123]

@jmarantz big +1 on killing the statics. I hate them also.