lkml.org 
[lkml]   [2013]   [Dec]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 12/18] mm: numa: Defer TLB flush for THP migration as long as possible
    On 12/09/2013 02:09 AM, Mel Gorman wrote:

    > diff --git a/mm/migrate.c b/mm/migrate.c
    > index cfb4190..5372521 100644
    > --- a/mm/migrate.c
    > +++ b/mm/migrate.c
    > @@ -1759,6 +1759,12 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
    > goto out_fail;
    > }
    >
    > + /* PTL provides a memory barrier with change_protection_range */
    > + ptl = pmd_lock(mm, pmd);
    > + if (tlb_flush_pending(mm))
    > + flush_tlb_range(vma, mmun_start, mmun_end);
    > + spin_unlock(ptl);
    > +
    > /* Prepare a page as a migration target */
    > __set_page_locked(new_page);
    > SetPageSwapBacked(new_page);

    I don't think there is a need for that extra memory barrier.

    On the "set_tlb_flush_pending, turn ptes into NUMA ones" side, we
    have a barrier in the form of the page table lock.

    We only end up in this code path if the pte/pmd already is a NUMA
    one, and we take several spinlocks along the way to doing this test.
    That provides for the memory barrier in this code path.

    --
    All rights reversed


    \
     
     \ /
      Last update: 2013-12-09 17:41    [W:4.041 / U:0.056 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site