Merge bitcoin/bitcoin#28512: doc: Be vague instead of wrong about MALLOC_ARENA_MAX

12f7257b8f doc: Be vague instead of wrong about MALLOC_ARENA_MAX (Tim Ruffing)

Pull request description:

  Before this commit, we claim that glibc's malloc implementation uses 2 arenas by default. But that's true only on 32-bit systems, and even there, it uses *up* to 2 arenas.

  This commit fixes the wrong statement. The new statement is intentionally vague to reduce our maintenance burden.

  For details, see:
  https://www.gnu.org/software/libc/manual/html_node/Memory-Allocation-Tunables.html#index-glibc_002emalloc_002earena_005fmax

  Noticed in:
  https://github.com/bitcoin/bitcoin/pull/27642#issuecomment-1728103427

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  fanquake:
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fanquake 2023-09-24 18:54:10 +01:00
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@ -43,7 +43,7 @@ threads take up 8MiB for the thread stack on a 64-bit system, and 4MiB in a
## Linux specific
By default, glibc will create up to two heap arenas per core. This is known to cause excessive memory usage in some scenarios. To avoid this make a script that sets `MALLOC_ARENA_MAX` before starting bitcoind:
By default, glibc's implementation of `malloc` may use more than one arena. This is known to cause excessive memory usage in some scenarios. To avoid this, make a script that sets `MALLOC_ARENA_MAX` before starting bitcoind:
```bash
#!/usr/bin/env bash