More comments below.
>>-----Original Message-----
>>From: [email protected]
>>[mailto:[email protected]] On Behalf Of Adam Litke
>>Sent: Wednesday, September 07, 2005 5:59 AM
>>To: [email protected]
>>Cc: ADAM G. LITKE [imap]
>>Subject: Re: [PATCH 2/3 htlb-fault] Demand faulting for hugetlb
>>
>>Below is a patch to implement demand faulting for huge pages. The
main
>>motivation for changing from prefaulting to demand faulting is so that
>>huge page memory areas can be allocated according to NUMA policy.
>>@@ -277,18 +277,20 @@ int copy_hugetlb_page_range(struct mm_st
>> unsigned long addr = vma->vm_start;
>> unsigned long end = vma->vm_end;
>>
>>- while (addr < end) {
>>+ for (; addr < end; addr += HPAGE_SIZE) {
>>+ src_pte = huge_pte_offset(src, addr);
>>+ if (!src_pte || pte_none(*src_pte))
>>+ continue;
>>+
>> dst_pte = huge_pte_alloc(dst, addr);
>> if (!dst_pte)
>> goto nomem;
>>- src_pte = huge_pte_offset(src, addr);
>>- BUG_ON(!src_pte || pte_none(*src_pte)); /* prefaulted */
>>+ BUG_ON(!src_pte);
Should this BUG_ON be deleted?
>> entry = *src_pte;
>> ptepage = pte_page(entry);
>> get_page(ptepage);
>> add_mm_counter(dst, rss, HPAGE_SIZE / PAGE_SIZE);
>> set_huge_pte_at(dst, addr, dst_pte, entry);
>>- addr += HPAGE_SIZE;
>> }
>> return 0;
>>
>>+int hugetlb_pte_fault(struct mm_struct *mm, struct vm_area_struct
*vma,
>>+ unsigned long address, int write_access)
>>+{
>>+ int ret = VM_FAULT_MINOR;
>>+ unsigned long idx;
>>+ pte_t *pte;
>>+ struct page *page;
>>+ struct address_space *mapping;
>>+
>>+ BUG_ON(vma->vm_start & ~HPAGE_MASK);
>>+ BUG_ON(vma->vm_end & ~HPAGE_MASK);
>>+ BUG_ON(!vma->vm_file);
>>+
>>+ pte = huge_pte_alloc(mm, address);
Why to call huge_pte_alloc again? Hugetlb_fault already calls it.
>>+ if (!pte) {
>>+ ret = VM_FAULT_SIGBUS;
>>+ goto out;
>>+ }
>>+ if (! pte_none(*pte))
>>+ goto flush;
>>+
>>+ mapping = vma->vm_file->f_mapping;
>>+ idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
>>+ + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
>>+retry:
>>+ page = find_get_page(mapping, idx);
>>+ if (!page) {
>>+ /* charge the fs quota first */
>>+ if (hugetlb_get_quota(mapping)) {
>>+ ret = VM_FAULT_SIGBUS;
>>+ goto out;
>>+ }
>>+ page = alloc_huge_page();
>>+ if (!page) {
>>+ hugetlb_put_quota(mapping);
>>+ ret = VM_FAULT_SIGBUS;
>>+ goto out;
>>+ }
>>+ if (add_to_page_cache(page, mapping, idx, GFP_ATOMIC)) {
>>+ put_page(page);
>>+ goto retry;
>>+ }
>>+ unlock_page(page);
>>+ }
>>+ add_mm_counter(mm, rss, HPAGE_SIZE / PAGE_SIZE);
>>+ set_huge_pte_at(mm, address, pte, make_huge_pte(vma, page));
>>+flush:
>>+ flush_tlb_page(vma, address);
>>+out:
>>+ return ret;
>>+}
>>+
>>+int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>>+ unsigned long address, int write_access)
>>+{
>>+ pte_t *ptep;
>>+ int rc = VM_FAULT_MINOR;
>>+
>>+ spin_lock(&mm->page_table_lock);
>>+
>>+ ptep = huge_pte_alloc(mm, address & HPAGE_MASK);
The alignment is not needed. How about change it to ptep =
huge_pte_alloc(mm, address)?
>>+ if (! ptep) {
>>+ rc = VM_FAULT_SIGBUS;
>>+ goto out;
>>+ }
>>+ if (pte_none(*ptep))
>>+ rc = hugetlb_pte_fault(mm, vma, address, write_access);
In function hugetlb_pte_fault, if(!pte_none(*ptep)), tlb page will be
flushed, but here is doesn't. Why?
>>+out:
>>+ spin_unlock(&mm->page_table_lock);
>>+ return rc;
>>+}
-
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