Subject: [RFC 0/4] mm, swap: Enable THP SWAP for PowerPC Book3S64

From: "Ritesh Harjani (IBM)" <[email-masked]>
Date: Tue, 9 Jun 2026 18:49:30 +0530

On PowerPC Book3S64, MMU is selected at runtime, so macros like PMD_SHIFT are
effectively runtime variables in the Book3S64 code. THP swap code uses these
macros for e.g. to size some of its array data structures based on PMD_ORDER.
This patch series makes that usage dependent on the runtime variable.

Sayali did some performance runs of this on Book3S64 with Radix and it gives
40-50% performance improvement. We also plan to run it with Hash, will soon
update the results.

Note that this patch series is based out of linux-next (next-20260608).

Ritesh Harjani (IBM) (4):
  include/linux/swap.h: Remove unused leftovers
  mm, swap: make SWAPFILE_CLUSTER runtime
  mm, swap: make SWAP_NR_ORDERS runtime
  powerpc: Kconfig: Enable THP_SWAP on Book3S64

 arch/powerpc/platforms/Kconfig.cputype |   1 +
 include/linux/swap.h                   |  17 +---
 mm/swap.h                              |   5 +-
 mm/swap_table.h                        |   6 +-
 mm/swapfile.c                          | 132 ++++++++++++++++++-------
 5 files changed, 106 insertions(+), 55 deletions(-)

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2.39.5