powerpc/64s/radix: Don't prefetch DAR in update_mmu_cache

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The idea behind this prefetch was to kick off a page table walk before
returning from the fault, getting some pipelining advantage.

But this never showed up any noticable performance advantage, and in
fact with KUAP the prefetches are actually blocked and cause some
kind of micro-architectural fault. Removing this improves page fault
microbenchmark performance by about 9%.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Keep the early return in update_mmu_cache()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200504122907.49304-1-npiggin@gmail.com

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Nicholas Piggin 2020-05-04 22:29:07 +10:00 • committed by Michael Ellerman

parent e4f4ffa8a9

commit 18594f9b8c

3 changed files with 6 additions and 18 deletions

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7

arch/powerpc/include/asm/book3s/64/pgtable.h

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4

arch/powerpc/mm/book3s64/hash_utils.c

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13

arch/powerpc/mm/book3s64/pgtable.c

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