[llvm-bugs] [Bug 28310] New: Aarch64 memory benchmark performance vs ARMv7

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=28310

            Bug ID: 28310
           Summary: Aarch64 memory benchmark performance vs ARMv7
           Product: libraries
           Version: 3.8
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: AArch64
          Assignee: unassignedbugs at nondot.org
          Reporter: tulipawn at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 16635
  --> https://llvm.org/bugs/attachment.cgi?id=16635&action=edit
Benchmark files, cargo ready

Since yesterday, I've been playing with Rust on an `aarch64` Cortex-A53 Android
TV box (2GB RAM, Amlogic S905) that I'd converted to 64-bit Linux.

All's fine and good so far, except for memory benchmark performance, especially
using jemalloc, which is relatively worse compared to ARMv7 (and substantially
worse in absolute terms).

Am I not enabling some erratum perhaps? The native aarch64 binary_trees
benchmark (@23 tree depth) takes:

sysalloc 1m28s 5m10s 0m10s
jemalloc 1m35s 5m10s 0m53s

whereas, the corresponding ARMv7 binaries (running on the same 64-bit system):

sysalloc 1m9s 3m59s 0m19s
jemalloc 1m11s 3m58s 0m25s

@jmolloy I'm aware better performance using 32-bit pointers is probably
expected but what about jemalloc performance drop?

To reproduce, run `cargo build --release && time target/release/binary_trees
23` inside the binary_trees directory. Uncomment the first 2 lines in main.rs
to produce a sysalloc version.

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