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| author | Gerald Schaefer <gerald.schaefer@linux.ibm.com> | 2020-07-29 22:22:34 +0200 |
|---|---|---|
| committer | Heiko Carstens <hca@linux.ibm.com> | 2020-08-11 18:16:13 +0200 |
| commit | ba925fa35057a062ac98c3e8138b013ce4ce351c (patch) | |
| tree | 90e90da496783eecb3ae5ae33d65773d174bd5dd /arch/s390/mm | |
| parent | f0cbd3b83ed47803df941865f720934c69abb803 (diff) | |
| download | linux-ba925fa35057a062ac98c3e8138b013ce4ce351c.tar.bz2 | |
s390/gmap: improve THP splitting
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@vger.kernel.org> # v5.4+
Reported-by: Ilya Leoshkevich <iii@linux.ibm.com>
Tested-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Diffstat (limited to 'arch/s390/mm')
| -rw-r--r-- | arch/s390/mm/gmap.c | 27 |
1 files changed, 20 insertions, 7 deletions
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c index 190357ff86b3..46c1bf2a3b4b 100644 --- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -2485,23 +2485,36 @@ void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long bitmap[4], } 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 |