mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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04b67022fb
KASAN fills kernel page tables with repeated values to map several
TBs of the virtual memory to the single kasan_zero_page:
kasan_zero_p4d ->
kasan_zero_pud ->
kasan_zero_pmd->
kasan_zero_pte->
kasan_zero_page
Walking the whole KASAN shadow range takes a lot of time, especially
with 5-level page tables. Since we already know that all kasan page tables
eventually point to the kasan_zero_page we could call note_page()
right and avoid walking lower levels of the page tables.
This will not affect the output of the kernel_page_tables file,
but let us avoid spending time in page table walkers:
Before:
$ time cat /sys/kernel/debug/kernel_page_tables > /dev/null
real 0m55.855s
user 0m0.000s
sys 0m55.840s
After:
$ time cat /sys/kernel/debug/kernel_page_tables > /dev/null
real 0m0.054s
user 0m0.000s
sys 0m0.054s
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170724152558.24689-1-aryabinin@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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|---|---|---|
| .. | ||
| kmemcheck | ||
| amdtopology.c | ||
| debug_pagetables.c | ||
| dump_pagetables.c | ||
| extable.c | ||
| fault.c | ||
| highmem_32.c | ||
| hugetlbpage.c | ||
| ident_map.c | ||
| init_32.c | ||
| init_64.c | ||
| init.c | ||
| iomap_32.c | ||
| ioremap.c | ||
| kasan_init_64.c | ||
| kaslr.c | ||
| kmmio.c | ||
| Makefile | ||
| mem_encrypt_boot.S | ||
| mem_encrypt.c | ||
| mm_internal.h | ||
| mmap.c | ||
| mmio-mod.c | ||
| mpx.c | ||
| numa_32.c | ||
| numa_64.c | ||
| numa_emulation.c | ||
| numa_internal.h | ||
| numa.c | ||
| pageattr-test.c | ||
| pageattr.c | ||
| pat_internal.h | ||
| pat_rbtree.c | ||
| pat.c | ||
| pf_in.c | ||
| pf_in.h | ||
| pgtable_32.c | ||
| pgtable.c | ||
| physaddr.c | ||
| physaddr.h | ||
| pkeys.c | ||
| setup_nx.c | ||
| srat.c | ||
| testmmiotrace.c | ||
| tlb.c | ||