This patch makes optimistic check for swapin readahead
to increase thp collapse rate. Before getting swapped
out pages to memory, checks them and allows up to a
certain number. It also prints out using tracepoints
amount of unmapped ptes.
Signed-off-by: Ebru Akagunduz <ebru.akagun...@gmail.com>
---
Changes in v2:
- Nothing changed
Changes in v3:
- Define constant to specify exact tracepoint result (Vlastimil Babka)
include/linux/mm.h | 1 +
include/trace/events/huge_memory.h | 11 +++++++----
mm/huge_memory.c | 15 ++++++++++++---
3 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index bf341c0..eacf348 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -38,6 +38,7 @@
#define MM_ALLOC_HUGE_PAGE_FAIL 6
#define MM_CGROUP_CHARGE_FAIL 7
#define MM_COLLAPSE_ISOLATE_FAIL 5
+#define MM_EXCEED_SWAP_PTE 2
struct mempolicy;
struct anon_vma;
diff --git a/include/trace/events/huge_memory.h
b/include/trace/events/huge_memory.h
index cbc56fc..b6bdcc4 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -9,9 +9,9 @@
TRACE_EVENT(mm_khugepaged_scan_pmd,
TP_PROTO(struct mm_struct *mm, struct page *page, bool writable,
- bool referenced, int none_or_zero, int ret),
+ bool referenced, int none_or_zero, int ret, int unmapped),
- TP_ARGS(mm, page, writable, referenced, none_or_zero, ret),
+ TP_ARGS(mm, page, writable, referenced, none_or_zero, ret, unmapped),
TP_STRUCT__entry(
__field(struct mm_struct *, mm)
@@ -20,6 +20,7 @@ TRACE_EVENT(mm_khugepaged_scan_pmd,
__field(bool, referenced)
__field(int, none_or_zero)
__field(int, ret)
+ __field(int, unmapped)
),
TP_fast_assign(
@@ -29,15 +30,17 @@ TRACE_EVENT(mm_khugepaged_scan_pmd,
__entry->referenced = referenced;
__entry->none_or_zero = none_or_zero;
__entry->ret = ret;
+ __entry->unmapped = unmapped;
),
- TP_printk("mm=%p, page=%p, writable=%d, referenced=%d, none_or_zero=%d,
ret=%d",
+ TP_printk("mm=%p, page=%p, writable=%d, referenced=%d, none_or_zero=%d,
ret=%d, unmapped=%d",
__entry->mm,
__entry->page,
__entry->writable,
__entry->referenced,
__entry->none_or_zero,
- __entry->ret)
+ __entry->ret,
+ __entry->unmapped)
);
TRACE_EVENT(mm_collapse_huge_page,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 595edd9..b4cef9d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -24,6 +24,7 @@
#include <linux/migrate.h>
#include <linux/hashtable.h>
#include <linux/userfaultfd_k.h>
+#include <linux/swapops.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
@@ -2671,11 +2672,11 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
{
pmd_t *pmd;
pte_t *pte, *_pte;
- int ret = 0, none_or_zero = 0;
+ int ret = 0, none_or_zero = 0, unmapped = 0;
struct page *page = NULL;
unsigned long _address;
spinlock_t *ptl;
- int node = NUMA_NO_NODE;
+ int node = NUMA_NO_NODE, max_ptes_swap = HPAGE_PMD_NR/8;
bool writable = false, referenced = false;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
@@ -2691,6 +2692,14 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, _address += PAGE_SIZE) {
pte_t pteval = *_pte;
+ if (is_swap_pte(pteval)) {
+ if (++unmapped <= max_ptes_swap) {
+ continue;
+ } else {
+ ret = MM_EXCEED_SWAP_PTE;
+ goto out_unmap;
+ }
+ }
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
if (!userfaultfd_armed(vma) &&
++none_or_zero <= khugepaged_max_ptes_none) {
@@ -2755,7 +2764,7 @@ out_unmap:
}
out:
trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
- none_or_zero, ret);
+ none_or_zero, ret, unmapped);
return ret;
}
--
1.9.1
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