The patch titled
Subject: mm/swap: cache swap migration A/D bits support
has been added to the -mm mm-unstable branch. Its filename is
mm-swap-cache-swap-migration-a-d-bits-support.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swap-cache-swap-migration-a-d-bits-support.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm/swap: cache swap migration A/D bits support
Date: Thu, 11 Aug 2022 12:13:31 -0400
Introduce a variable swap_migration_ad_supported to cache whether the arch
supports swap migration A/D bits.
Here one thing to mention is that SWP_MIG_TOTAL_BITS will internally
reference the other macro MAX_PHYSMEM_BITS, which is a function call on
x86 (constant on all the rest of archs).
It's safe to reference it in swapfile_init() because when reaching here
we're already during initcalls level 4 so we must have initialized 5-level
pgtable for x86_64 (right after early_identify_cpu() finishes).
- start_kernel
- setup_arch
- early_cpu_init
- get_cpu_cap --> fetch from CPUID (including X86_FEATURE_LA57)
- early_identify_cpu --> clear X86_FEATURE_LA57 (if early lvl5 not enabled (USE_EARLY_PGTABLE_L5))
- arch_call_rest_init
- rest_init
- kernel_init
- kernel_init_freeable
- do_basic_setup
- do_initcalls --> calls swapfile_init() (initcall level 4)
This should slightly speed up the migration swap entry handlings.
Link: https://lkml.kernel.org/r/20220811161331.37055-8-peterx@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swapfile.h | 2 ++
include/linux/swapops.h | 7 +------
mm/swapfile.c | 8 ++++++++
3 files changed, 11 insertions(+), 6 deletions(-)
--- a/include/linux/swapfile.h~mm-swap-cache-swap-migration-a-d-bits-support
+++ a/include/linux/swapfile.h
@@ -10,5 +10,7 @@ extern struct swap_info_struct *swap_inf
extern unsigned long generic_max_swapfile_size(void);
/* Maximum swapfile size supported for the arch (not inclusive). */
extern unsigned long swapfile_maximum_size;
+/* Whether swap migration entry supports storing A/D bits for the arch */
+extern bool swap_migration_ad_supported;
#endif /* _LINUX_SWAPFILE_H */
--- a/include/linux/swapops.h~mm-swap-cache-swap-migration-a-d-bits-support
+++ a/include/linux/swapops.h
@@ -301,13 +301,8 @@ static inline swp_entry_t make_writable_
*/
static inline bool migration_entry_supports_ad(void)
{
- /*
- * max_swapfile_size() returns the max supported swp-offset plus 1.
- * We can support the migration A/D bits iff the pfn swap entry has
- * the offset large enough to cover all of them (PFN, A & D bits).
- */
#ifdef CONFIG_SWAP
- return swapfile_maximum_size >= (1UL << SWP_MIG_TOTAL_BITS);
+ return swap_migration_ad_supported;
#else /* CONFIG_SWAP */
return false;
#endif /* CONFIG_SWAP */
--- a/mm/swapfile.c~mm-swap-cache-swap-migration-a-d-bits-support
+++ a/mm/swapfile.c
@@ -64,6 +64,9 @@ EXPORT_SYMBOL_GPL(nr_swap_pages);
long total_swap_pages;
static int least_priority = -1;
unsigned long swapfile_maximum_size;
+#ifdef CONFIG_MIGRATION
+bool swap_migration_ad_supported;
+#endif /* CONFIG_MIGRATION */
static const char Bad_file[] = "Bad swap file entry ";
static const char Unused_file[] = "Unused swap file entry ";
@@ -3680,6 +3683,11 @@ static int __init swapfile_init(void)
swapfile_maximum_size = arch_max_swapfile_size();
+#ifdef CONFIG_MIGRATION
+ if (swapfile_maximum_size >= (1UL << SWP_MIG_TOTAL_BITS))
+ swap_migration_ad_supported = true;
+#endif /* CONFIG_MIGRATION */
+
return 0;
}
subsys_initcall(swapfile_init);
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-smaps-dont-access-young-dirty-bit-if-pte-unpresent.patch
mm-uffd-reset-write-protection-when-unregister-with-wp-mode.patch
mm-x86-use-swp_type_bits-in-3-level-swap-macros.patch
mm-swap-comment-all-the-ifdef-in-swapopsh.patch
mm-swap-add-swp_offset_pfn-to-fetch-pfn-from-swap-entry.patch
mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd.patch
mm-remember-young-dirty-bit-for-page-migrations.patch
mm-swap-cache-maximum-swapfile-size-when-init-swap.patch
mm-swap-cache-swap-migration-a-d-bits-support.patch
