Naoya Horiguchi wrote: > Hi Kirill, > > On Fri, Sep 06, 2013 at 01:48:03PM +0300, Kirill A. Shutemov wrote: > > Naoya Horiguchi wrote: > > > Thp related code also uses per process mm->page_table_lock now. > > > So making it fine-grained can provide better performance. > > > > > > This patch makes thp support split page table lock by using page->ptl > > > of the pages storing "pmd_trans_huge" pmds. > > > > > > Some functions like pmd_trans_huge_lock() and page_check_address_pmd() > > > are expected by their caller to pass back the pointer of ptl, so this > > > patch adds to those functions new arguments for that. Rather than that, > > > this patch gives only straightforward replacement. > > > > > > ChangeLog v3: > > > - fixed argument of huge_pmd_lockptr() in copy_huge_pmd() > > > - added missing declaration of ptl in do_huge_pmd_anonymous_page() > > > > > > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > > > > Generally, looks good. Few notes: > > > > I believe you need to convert __pte_alloc() to new locking. Not sure about > > __pte_alloc_kernel(). > > Have you check all rest mm->page_table_lock, that they shouldn't be > > converted to new locking? > > I thought that keeping __pte_alloc() using mm->page_table_lock was safe > because it uses bare mm->page_table_lock instead of pte_lockptr() even > before this patchset, but not 100% sure. > __pte_alloc() (and its family) are used in normal page path, so if it's > not safe, we've lived with unsafe code for very long (maybe since 2005). > Anyway, converting __pte_alloc() into split ptl could improve performance > (though we need testing to know what amount), so I'll try that. No, before the patch mm->page_table_lock is what we need: it serializes setting up pmd, not adding pte to pmd and it's subject to change with new locking model. -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>