Messages in this thread | | | Subject | Re: [PATCH] mm,do_huge_pmd_numa_page: remove unnecessary TLB flushing code | From | Christian Borntraeger <> | Date | Tue, 20 Jul 2021 16:25:37 +0200 |
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On 20.07.21 08:55, Huang Ying wrote: > Before the commit c5b5a3dd2c1f ("mm: thp: refactor NUMA fault > handling"), the TLB flushing is done in do_huge_pmd_numa_page() itself > via flush_tlb_range(). > > But after commit c5b5a3dd2c1f ("mm: thp: refactor NUMA fault > handling"), the TLB flushing is done in migrate_pages() as in the > following code path anyway. > > do_huge_pmd_numa_page > migrate_misplaced_page > migrate_pages > > So now, the TLB flushing code in do_huge_pmd_numa_page() becomes > unnecessary. So the code is deleted in this patch to simplify the > code. This is only code cleanup, there's no visible performance > difference. > > Signed-off-by: "Huang, Ying" <ying.huang@intel.com> > Cc: Yang Shi <shy828301@gmail.com> > Cc: Dan Carpenter <dan.carpenter@oracle.com> > Cc: Mel Gorman <mgorman@suse.de> > Cc: Christian Borntraeger <borntraeger@de.ibm.com> > Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com> > Cc: Heiko Carstens <hca@linux.ibm.com> > Cc: Hugh Dickins <hughd@google.com> > Cc: Andrea Arcangeli <aarcange@redhat.com> > Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Vasily Gorbik <gor@linux.ibm.com> > Cc: Zi Yan <ziy@nvidia.com> > --- > mm/huge_memory.c | 26 -------------------------- > 1 file changed, 26 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index afff3ac87067..9f21e44c9030 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1440,32 +1440,6 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf) > goto out; > } > > - /* > - * Since we took the NUMA fault, we must have observed the !accessible > - * bit. Make sure all other CPUs agree with that, to avoid them > - * modifying the page we're about to migrate. > - * > - * Must be done under PTL such that we'll observe the relevant > - * inc_tlb_flush_pending(). > - * > - * We are not sure a pending tlb flush here is for a huge page > - * mapping or not. Hence use the tlb range variant > - */ > - if (mm_tlb_flush_pending(vma->vm_mm)) { > - flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); > - /* > - * change_huge_pmd() released the pmd lock before > - * invalidating the secondary MMUs sharing the primary > - * MMU pagetables (with ->invalidate_range()). The > - * mmu_notifier_invalidate_range_end() (which > - * internally calls ->invalidate_range()) in > - * change_pmd_range() will run after us, so we can't > - * rely on it here and we need an explicit invalidate. > - */ > - mmu_notifier_invalidate_range(vma->vm_mm, haddr, > - haddr + HPAGE_PMD_SIZE); > - } > CC Paolo/KVM list so we also remove the mmu notifier here. Do we need those now in migrate_pages? I am not an expert in that code, but I cant find an equivalent mmu_notifier in migrate_misplaced_pages. I might be totally wrong, just something that I noticed.
> pmd = pmd_modify(oldpmd, vma->vm_page_prot); > page = vm_normal_page_pmd(vma, haddr, pmd); > if (!page) >
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