From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx195.postini.com [74.125.245.195]) by kanga.kvack.org (Postfix) with SMTP id 192076B004D for ; Tue, 13 Nov 2012 05:26:02 -0500 (EST) Received: by mail-ea0-f169.google.com with SMTP id k11so3390227eaa.14 for ; Tue, 13 Nov 2012 02:26:00 -0800 (PST) Date: Tue, 13 Nov 2012 11:25:55 +0100 From: Ingo Molnar Subject: Re: [PATCH 14/19] mm: mempolicy: Add MPOL_MF_LAZY Message-ID: <20121113102555.GE21522@gmail.com> References: <1352193295-26815-1-git-send-email-mgorman@suse.de> <1352193295-26815-15-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1352193295-26815-15-git-send-email-mgorman@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Peter Zijlstra , Andrea Arcangeli , Rik van Riel , Johannes Weiner , Hugh Dickins , Thomas Gleixner , Linus Torvalds , Andrew Morton , Linux-MM , LKML * Mel Gorman wrote: > From: Lee Schermerhorn > > NOTE: Once again there is a lot of patch stealing and the end result > is sufficiently different that I had to drop the signed-offs. > Will re-add if the original authors are ok with that. > > This patch adds another mbind() flag to request "lazy migration". The > flag, MPOL_MF_LAZY, modifies MPOL_MF_MOVE* such that the selected > pages are marked PROT_NONE. The pages will be migrated in the fault > path on "first touch", if the policy dictates at that time. > > "Lazy Migration" will allow testing of migrate-on-fault via mbind(). > Also allows applications to specify that only subsequently touched > pages be migrated to obey new policy, instead of all pages in range. > This can be useful for multi-threaded applications working on a > large shared data area that is initialized by an initial thread > resulting in all pages on one [or a few, if overflowed] nodes. > After PROT_NONE, the pages in regions assigned to the worker threads > will be automatically migrated local to the threads on 1st touch. > > Signed-off-by: Mel Gorman > --- > include/linux/mm.h | 3 + > include/uapi/linux/mempolicy.h | 13 ++- > mm/mempolicy.c | 176 ++++++++++++++++++++++++++++++++++++---- > 3 files changed, 174 insertions(+), 18 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index fa06804..eed70f8 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1548,6 +1548,9 @@ static inline pgprot_t vm_get_page_prot(unsigned long vm_flags) > } > #endif > > +void change_prot_numa(struct vm_area_struct *vma, > + unsigned long start, unsigned long end); > + > struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr); > int remap_pfn_range(struct vm_area_struct *, unsigned long addr, > unsigned long pfn, unsigned long size, pgprot_t); > diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h > index 472de8a..6a1baae 100644 > --- a/include/uapi/linux/mempolicy.h > +++ b/include/uapi/linux/mempolicy.h > @@ -49,9 +49,16 @@ enum mpol_rebind_step { > > /* Flags for mbind */ > #define MPOL_MF_STRICT (1<<0) /* Verify existing pages in the mapping */ > -#define MPOL_MF_MOVE (1<<1) /* Move pages owned by this process to conform to mapping */ > -#define MPOL_MF_MOVE_ALL (1<<2) /* Move every page to conform to mapping */ > -#define MPOL_MF_INTERNAL (1<<3) /* Internal flags start here */ > +#define MPOL_MF_MOVE (1<<1) /* Move pages owned by this process to conform > + to policy */ > +#define MPOL_MF_MOVE_ALL (1<<2) /* Move every page to conform to policy */ > +#define MPOL_MF_LAZY (1<<3) /* Modifies '_MOVE: lazy migrate on fault */ > +#define MPOL_MF_INTERNAL (1<<4) /* Internal flags start here */ > + > +#define MPOL_MF_VALID (MPOL_MF_STRICT | \ > + MPOL_MF_MOVE | \ > + MPOL_MF_MOVE_ALL | \ > + MPOL_MF_LAZY) > > /* > * Internal flags that share the struct mempolicy flags word with > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index df1466d..abe2e45 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -90,6 +90,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -566,6 +567,136 @@ static inline int check_pgd_range(struct vm_area_struct *vma, > } > > /* > + * Here we search for not shared page mappings (mapcount == 1) and we > + * set up the pmd/pte_numa on those mappings so the very next access > + * will fire a NUMA hinting page fault. > + */ > +static int > +change_prot_numa_range(struct mm_struct *mm, struct vm_area_struct *vma, > + unsigned long address) > +{ > + pgd_t *pgd; > + pud_t *pud; > + pmd_t *pmd; > + pte_t *pte, *_pte; > + struct page *page; > + unsigned long _address, end; > + spinlock_t *ptl; > + int ret = 0; > + > + VM_BUG_ON(address & ~PAGE_MASK); > + > + pgd = pgd_offset(mm, address); > + if (!pgd_present(*pgd)) > + goto out; > + > + pud = pud_offset(pgd, address); > + if (!pud_present(*pud)) > + goto out; > + > + pmd = pmd_offset(pud, address); > + if (pmd_none(*pmd)) > + goto out; > + > + if (pmd_trans_huge_lock(pmd, vma) == 1) { > + int page_nid; > + ret = HPAGE_PMD_NR; > + > + VM_BUG_ON(address & ~HPAGE_PMD_MASK); > + > + if (pmd_numa(*pmd)) { > + spin_unlock(&mm->page_table_lock); > + goto out; > + } > + > + page = pmd_page(*pmd); > + > + /* only check non-shared pages */ > + if (page_mapcount(page) != 1) { > + spin_unlock(&mm->page_table_lock); > + goto out; > + } > + > + page_nid = page_to_nid(page); > + > + if (pmd_numa(*pmd)) { > + spin_unlock(&mm->page_table_lock); > + goto out; > + } > + > + set_pmd_at(mm, address, pmd, pmd_mknuma(*pmd)); > + /* defer TLB flush to lower the overhead */ > + spin_unlock(&mm->page_table_lock); > + goto out; > + } > + > + if (pmd_trans_unstable(pmd)) > + goto out; > + VM_BUG_ON(!pmd_present(*pmd)); > + > + end = min(vma->vm_end, (address + PMD_SIZE) & PMD_MASK); > + pte = pte_offset_map_lock(mm, pmd, address, &ptl); > + for (_address = address, _pte = pte; _address < end; > + _pte++, _address += PAGE_SIZE) { > + pte_t pteval = *_pte; > + if (!pte_present(pteval)) > + continue; > + if (pte_numa(pteval)) > + continue; > + page = vm_normal_page(vma, _address, pteval); > + if (unlikely(!page)) > + continue; > + /* only check non-shared pages */ > + if (page_mapcount(page) != 1) > + continue; > + > + if (pte_numa(pteval)) > + continue; > + > + set_pte_at(mm, _address, _pte, pte_mknuma(pteval)); > + > + /* defer TLB flush to lower the overhead */ > + ret++; > + } > + pte_unmap_unlock(pte, ptl); > + > + if (ret && !pmd_numa(*pmd)) { > + spin_lock(&mm->page_table_lock); > + set_pmd_at(mm, address, pmd, pmd_mknuma(*pmd)); > + spin_unlock(&mm->page_table_lock); > + /* defer TLB flush to lower the overhead */ > + } > + > +out: > + return ret; > +} > + > +/* Assumes mmap_sem is held */ > +void > +change_prot_numa(struct vm_area_struct *vma, > + unsigned long address, unsigned long end) > +{ > + struct mm_struct *mm = vma->vm_mm; > + int progress = 0; > + > + while (address < vma->vm_end) { > + VM_BUG_ON(address < vma->vm_start || > + address + PAGE_SIZE > vma->vm_end); > + > + progress += change_prot_numa_range(mm, vma, address); > + address = (address + PMD_SIZE) & PMD_MASK; > + } > + > + /* > + * Flush the TLB for the mm to start the NUMA hinting > + * page faults after we finish scanning this vma part. > + */ > + mmu_notifier_invalidate_range_start(vma->vm_mm, address, end); > + flush_tlb_range(vma, address, end); > + mmu_notifier_invalidate_range_end(vma->vm_mm, address, end); > +} > + Here you are paying a heavy price for the earlier design mistake, for forking into per arch approach - the NUMA version of change_protection() had to be open-coded: > include/linux/mm.h | 3 + > include/uapi/linux/mempolicy.h | 13 ++- > mm/mempolicy.c | 176 ++++++++++++++++++++++++++++++++++++---- > 3 files changed, 174 insertions(+), 18 deletions(-) Compare it to the generic version that Peter used: include/uapi/linux/mempolicy.h | 13 ++++++++--- mm/mempolicy.c | 49 +++++++++++++++++++++++++++--------------- 2 files changed, 42 insertions(+), 20 deletions(-) and the cleanliness and maintainability advantages are obvious. So without some really good arguments in favor of your approach NAK on that complex approach really. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org