arm64: clear_page[s] using memset

There is no need to try to second-guess the compiler when
clearing memory. Just call memset() like everyone else.

Since memset() already has an architecture-local MOPS
optimization, we do not need to do anything else to preserve
the MOPS optimization.

While at it, implement the shorthand for directly calling
the new prototype clear_pages() for larger page chunks.

No performance regressions can be seen, the fastpath
benchmarks differences are in the noise.

Usama Anjum tested next-20260821 with one warm-up and three repeats
in four sessions, for a total of 12 measured runs. The commands were:

  perf bench mem memset -k 1GB -f default -s 16GB
  perf bench mem mmap -p 1GB -f demand -s 32GB -l 5
  perf bench mem mmap -p 4KB -f demand -s 32GB -l 5

The results were:

aws-m7g.metal:
  Benchmark    Base bytes/sec   Change with patch
  memset 1GB   63932542232.12                1.92%
  mmap 1GB     63272579168.03               -0.57%
  mmap 4KB     49692830849.48               -1.11%

cesw-aarch64-ampereone-1s-a192-32x:
  Benchmark    Base bytes/sec   Change with patch
  memset 1GB   33895562998.71                0.25%
  mmap 1GB     34338454210.17                1.16%
  mmap 4KB     25687107580.90               -0.85%

Assisted-by: LLM
Suggested-by: Will Deacon <will@kernel.org>
Tested-by: Usama Anjum <usama.anjum@arm.com>
Link: https://lore.kernel.org/linux-arm-kernel/20260303-aarch64-clear-pages-v1-1-ad0c3ee9a555@kernel.org/
Link: https://lore.kernel.org/linux-arm-kernel/67ab6c51-4511-46ab-931b-a4323551147a@arm.com/
Signed-off-by: Linus Walleij <linusw@kernel.org>
Reviewed-by: Leonardo Bras <leo.bras@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

0 files changed, 0 insertions, 0 deletions