THP_SWAP has been proven to improve the swap throughput significantly
on x86_64 according to commit
bd4c82c22c367e ("mm, THP, swap: delay
splitting THP after swapped out").
As long as arm64 uses 4K page size, it is quite similar with x86_64
by having 2MB PMD THP. THP_SWAP is architecture-independent, thus,
enabling it on arm64 will benefit arm64 as well.
A corner case is that MTE has an assumption that only base pages
can be swapped. We won't enable THP_SWAP for ARM64 hardware with
MTE support until MTE is reworked to coexist with THP_SWAP.
A micro-benchmark is written to measure thp swapout throughput as
below,
unsigned long long tv_to_ms(struct timeval tv)
{
return tv.tv_sec * 1000 + tv.tv_usec / 1000;
}
main()
{
struct timeval tv_b, tv_e;;
#define SIZE 400*1024*1024
volatile void *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (!p) {
perror("fail to get memory");
exit(-1);
}
madvise(p, SIZE, MADV_HUGEPAGE);
memset(p, 0x11, SIZE); /* write to get mem */
gettimeofday(&tv_b, NULL);
madvise(p, SIZE, MADV_PAGEOUT);
gettimeofday(&tv_e, NULL);
printf("swp out bandwidth: %ld bytes/ms\n",
SIZE/(tv_to_ms(tv_e) - tv_to_ms(tv_b)));
}
Testing is done on rk3568 64bit Quad Core Cortex-A55 platform -
ROCK 3A.
thp swp throughput w/o patch: 2734bytes/ms (mean of 10 tests)
thp swp throughput w/ patch: 3331bytes/ms (mean of 10 tests)
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Steven Price <steven.price@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Link: https://lore.kernel.org/r/20220720093737.133375-1-21cnbao@gmail.com
Signed-off-by: Will Deacon <will@kernel.org>
select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
select ARCH_WANT_LD_ORPHAN_WARN
select ARCH_WANTS_NO_INSTR
+ select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARM_AMBA
select ARM_ARCH_TIMER
__flush_tlb_range(vma, addr, end, PUD_SIZE, false, 1)
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+static inline bool arch_thp_swp_supported(void)
+{
+ return !system_supports_mte();
+}
+#define arch_thp_swp_supported arch_thp_swp_supported
+
/*
* Outside of a few very special situations (e.g. hibernation), we always
* use broadcast TLB invalidation instructions, therefore a spurious page
return split_huge_page_to_list(&folio->page, list);
}
+/*
+ * archs that select ARCH_WANTS_THP_SWAP but don't support THP_SWP due to
+ * limitations in the implementation like arm64 MTE can override this to
+ * false
+ */
+#ifndef arch_thp_swp_supported
+static inline bool arch_thp_swp_supported(void)
+{
+ return true;
+}
+#endif
+
#endif /* _LINUX_HUGE_MM_H */
entry.val = 0;
if (folio_test_large(folio)) {
- if (IS_ENABLED(CONFIG_THP_SWAP))
+ if (IS_ENABLED(CONFIG_THP_SWAP) && arch_thp_swp_supported())
get_swap_pages(1, &entry, folio_nr_pages(folio));
goto out;
}