use lru cache compileunit and we can configure cache size

[anjiahao1]

In some larger ELF files, traversing the CUs may cause an OOM use lru and set a cache size, can avoid it

[sevaa]

Thank you. In general, a memory saving mode is something users have requested in the past. That said, I am not convinced that memoizing this particular function is the right way to do it. When scrolling through a CU, the library will retain DIE objects in ways other than _dielist/_diemap - for example by keeping _parent. Also, the LRU caches that you build will be accounted on per-CU basis - that technically does not clamp the global memory consumption.

If your scenario involves scrolling through all CUs in a binary, consider force-clearing the CU cache in the DWARFInfo once you are done with it. You will get more memory saving from that.

And also, please do not submit PRs before the autotest passes.

[eliben]

@sevaa how about moving this discussion to a separate issue to collect it all in one place

[sevaa]

#586

[anjiahao1]

ok, thanks @sevaa @eliben