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Subject[PATCH 5/5] x86: mremap speedup - Enable HAVE_MOVE_PUD
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HAVE_MOVE_PUD enables remapping pages at the PUD level if both the
source and destination addresses are PUD-aligned.

With HAVE_MOVE_PUD enabled it can be inferred that there is approximately
a 13x improvement in performance on x86. (See data below).

------- Test Results ---------

The following results were obtained using a 5.4 kernel, by remapping
a PUD-aligned, 1GB sized region to a PUD-aligned destination.
The results from 10 iterations of the test are given below:

Total mremap times for 1GB data on x86. All times are in nanoseconds.

Control HAVE_MOVE_PUD

180394 15089
235728 14056
238931 25741
187330 13838
241742 14187
177925 14778
182758 14728
160872 14418
205813 15107
245722 13998

205721.5 15594 <-- Mean time in nanoseconds

A 1GB mremap completion time drops from ~205 microseconds
to ~15 microseconds on x86. (~13x speed up).

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
arch/x86/Kconfig | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7101ac64bb20..ff6e2755cab8 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -198,6 +198,7 @@ config X86
select HAVE_MIXED_BREAKPOINTS_REGS
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_MOVE_PMD
+ select HAVE_MOVE_PUD
select HAVE_NMI
select HAVE_OPROFILE
select HAVE_OPTPROBES
--
2.28.0.709.gb0816b6eb0-goog
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