From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752393AbcADUas (ORCPT ); Mon, 4 Jan 2016 15:30:48 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:36358 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751678AbcADUap (ORCPT ); Mon, 4 Jan 2016 15:30:45 -0500 Date: Mon, 4 Jan 2016 22:30:42 +0200 From: "Kirill A. Shutemov" To: Matthew Wilcox Cc: Matthew Wilcox , linux-mm@kvack.org, linux-nvdimm@ml01.01.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH 1/8] mm: Add optional support for PUD-sized transparent hugepages Message-ID: <20160104203041.GB13515@node.shutemov.name> References: <1450974037-24775-1-git-send-email-matthew.r.wilcox@intel.com> <1450974037-24775-2-git-send-email-matthew.r.wilcox@intel.com> <20151228100551.GA4589@node.shutemov.name> <20160102170638.GL2457@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160102170638.GL2457@linux.intel.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 02, 2016 at 12:06:38PM -0500, Matthew Wilcox wrote: > On Mon, Dec 28, 2015 at 12:05:51PM +0200, Kirill A. Shutemov wrote: > > On Thu, Dec 24, 2015 at 11:20:30AM -0500, Matthew Wilcox wrote: > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > > index 4bf3811..e14634f 100644 > > > --- a/include/linux/mm.h > > > +++ b/include/linux/mm.h > > > @@ -1958,6 +1977,17 @@ static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd) > > > return ptl; > > > } > > > > > > +/* > > > + * No scalability reason to split PUD locks yet, but follow the same pattern > > > + * as the PMD locks to make it easier if we have to. > > > + */ > > > > I don't think it makes any good unless you convert all other places where > > we use page_table_lock to protect pud table (like __pud_alloc()) to the > > same API. > > I think this would deserve separate patch. > > Sure, a separate patch to convert existing users of the PTL. But I > don't think it does any harm to introduce the PUD version of the PMD API. > Maybe with a comment indicating that tere is significant work to be done > in converting existing users to this API? I think that's fine with the fat comment around pud_lock() definition. > > > diff --git a/mm/memory.c b/mm/memory.c > > > index 416b129..7328df0 100644 > > > --- a/mm/memory.c > > > +++ b/mm/memory.c > > > @@ -1220,9 +1220,27 @@ static inline unsigned long zap_pud_range(struct mmu_gather *tlb, > > > pud = pud_offset(pgd, addr); > > > do { > > > next = pud_addr_end(addr, end); > > > + if (pud_trans_huge(*pud) || pud_devmap(*pud)) { > > > + if (next - addr != HPAGE_PUD_SIZE) { > > > +#ifdef CONFIG_DEBUG_VM > > > > IS_ENABLED(CONFIG_DEBUG_VM) ? > > > > > + if (!rwsem_is_locked(&tlb->mm->mmap_sem)) { > > > + pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n", > > > + __func__, addr, end, > > > + vma->vm_start, > > > + vma->vm_end); > > > > dump_vma(), I guess. > > These two issues are copy-and-paste from the existing PMD code. I'm happy > to update the PMD code to the new-and-improved way of doing things; > I'm just not keen to have the PMD and PUD code diverge unnecessarily. Yes, please update PMD too. It looks ugly. VM_BUG_ON_VMA() is probably right way to deal with this. -- Kirill A. Shutemov