[PATCH] D59797: [COFF] Reorder fields in Chunk and SectionChunk to reduce their size

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

In D59797#1442250 <https://reviews.llvm.org/D59797#1442250>, @aganea wrote:

> > @rnk wrote:
> >  This reduces the total size of all LLD heap allocations by 5.22%
>
> What is the total heap size before/after? What percentage of that heap size is used by Chunks? How many of them do you have?


I used the VS memory profiling tool and used the type view to see the most commonly allocated types. "void" just means allocations whose type wasn't determined, and a lot of it comes from vectors, specifically the new `RelocTargets` vector @mstorsjo added.

  Before:
  heap usage: 176,077 KB
  type                                    count           size
  lld-link.exe!lld::coff::SectionChunk    370,809         71,195,328
  void                                    251,990         63,254,440
  lld-link.exe!lld::coff::Symbol[]        444,020         24,865,120
  lld-link.exe!lld::coff::DefinedRegular  379,729         18,226,992
  char[]  249     1,233,585
  
  After:
  heap usage: 167,335 KB
  type                                   |count          |byte size
  ---------------------------------------|---------------|-------------
  void                                   |251,990        |63,254,440
  lld-link.exe!lld::coff::SectionChunk   |370,809        |62,295,912
  lld-link.exe!lld::coff::Symbol[]       |444,020        |24,865,120
  lld-link.exe!lld::coff::DefinedRegular |379,729        |18,226,992
  char[]                                 |249            |1,233,585
  
  5.22% heap usage reduction


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D59797/new/

https://reviews.llvm.org/D59797