From: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
commit ba925fa35057a062ac98c3e8138b013ce4ce351c upstream.
During s390_enable_sie(), we need to take care of splitting all qemu user
process THP mappings. This is currently done with follow_page(FOLL_SPLIT),
by simply iterating over all vma ranges, with PAGE_SIZE increment.
This logic is sub-optimal and can result in a lot of unnecessary overhead,
especially when using qemu and ASAN with large shadow map. Ilya reported
significant system slow-down with one CPU busy for a long time and overall
unresponsiveness.
Fix this by using walk_page_vma() and directly calling split_huge_pmd()
only for present pmds, which greatly reduces overhead.
Cc: <stable@xxxxxxxxxxxxxxx> # v5.4+
Reported-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Tested-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Signed-off-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/mm/gmap.c | 27 ++++++++++++++++++++-------
1 file changed, 20 insertions(+), 7 deletions(-)
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2485,23 +2485,36 @@ void gmap_sync_dirty_log_pmd(struct gmap
}
EXPORT_SYMBOL_GPL(gmap_sync_dirty_log_pmd);
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static int thp_split_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
+ unsigned long end, struct mm_walk *walk)
+{
+ struct vm_area_struct *vma = walk->vma;
+
+ split_huge_pmd(vma, pmd, addr);
+ return 0;
+}
+
+static const struct mm_walk_ops thp_split_walk_ops = {
+ .pmd_entry = thp_split_walk_pmd_entry,
+};
+
static inline void thp_split_mm(struct mm_struct *mm)
{
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
struct vm_area_struct *vma;
- unsigned long addr;
for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
- for (addr = vma->vm_start;
- addr < vma->vm_end;
- addr += PAGE_SIZE)
- follow_page(vma, addr, FOLL_SPLIT);
vma->vm_flags &= ~VM_HUGEPAGE;
vma->vm_flags |= VM_NOHUGEPAGE;
+ walk_page_vma(vma, &thp_split_walk_ops, NULL);
}
mm->def_flags |= VM_NOHUGEPAGE;
-#endif
}
+#else
+static inline void thp_split_mm(struct mm_struct *mm)
+{
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
/*
* Remove all empty zero pages from the mapping for lazy refaulting
