[RESEND RFC PATCH 0/2] Enable vmalloc huge mappings by default on arm64

[Dev Jain <dev.jain@arm.com>]

In the quest for reducing TLB pressure via block mappings, enable huge
vmalloc by default on arm64 for BBML2-noabort systems which support kernel
live mapping split.

This series is an RFC, because I cannot get a performance improvement for
the usual benchmarks which we have. Currently, vmalloc follows an opt-in
approach for block mappings - the users calling vmalloc_huge() are the ones
which expect the most advantage from block mappings. Most users of
vmalloc(), kvmalloc() and kvzalloc() map a single page. After applying this
series, it is expected that a considerable number of users will produce
cont mappings, and probably none will produce PMD mappings.

I am asking for help from the community in testing - I believe that one of
the testing methods is xfstests: a lot of code uses the APIs mentioned
above. I am hoping that someone can jump in and run at least xfstests, and
probably some other tests which can take advantage of the reduced TLB
pressure from vmalloc cont mappings.

---
Patchset applies on Linus' master (d358e5254674).

Dev Jain (2):
  mm/vmalloc: Do not align size to huge size
  arm64/mm: Enable huge-vmalloc by default

 arch/arm64/include/asm/vmalloc.h |  6 +++++
 arch/arm64/mm/pageattr.c         |  4 +--
 include/linux/vmalloc.h          |  7 ++++++
 mm/vmalloc.c                     | 43 +++++++++++++++++++++++++-------
 4 files changed, 48 insertions(+), 12 deletions(-)

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2.30.2