From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chen, Kenneth W" Subject: [patch 2/2] htlb forget rss with pt sharing Date: Tue, 3 Oct 2006 03:01:17 -0700 Message-ID: <000201c6e6d2$deabcec0$bb80030a@amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: 'Hugh Dickins' , 'Andrew Morton' , 'Dave McCracken' Cc: linux-mm@kvack.org List-ID: Imprecise RSS accounting is an irritating ill effect with pt sharing. After consulted with several VM experts, I have tried various methods to solve that problem: (1) iterate through all mm_structs that share the PT and increment count; (2) keep RSS count in page table structure and then sum them up at reporting time. None of the above methods yield any satisfactory implementation. Since process RSS accounting is pure information only, I propose we don't count them at all for hugetlb page. rlimit has such field, though there is absolutely no enforcement on limiting that resource. One other method is to account all RSS at hugetlb mmap time regardless they are faulted or not. I opt for the simplicity of no accounting at all. Signed-off-by: Ken Chen --- ./mm/hugetlb.c.orig 2006-10-03 00:16:38.000000000 -0700 +++ ./mm/hugetlb.c 2006-10-03 00:19:45.000000000 -0700 @@ -344,7 +344,6 @@ int copy_hugetlb_page_range(struct mm_st entry = *src_pte; ptepage = pte_page(entry); get_page(ptepage); - add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE); set_huge_pte_at(dst, addr, dst_pte, entry); } spin_unlock(&src->page_table_lock); @@ -372,10 +371,6 @@ void __unmap_hugepage_range(struct vm_ar INIT_LIST_HEAD(&page_list); spin_lock(&mm->page_table_lock); - - /* Update high watermark before we lower rss */ - update_hiwater_rss(mm); - for (address = start; address < end; address += HPAGE_SIZE) { ptep = huge_pte_offset(mm, address); if (!ptep) @@ -390,9 +385,7 @@ void __unmap_hugepage_range(struct vm_ar page = pte_page(pte); list_add(&page->lru, &page_list); - add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE)); } - spin_unlock(&mm->page_table_lock); flush_tlb_range(vma, start, end); list_for_each_entry_safe(page, tmp, &page_list, lru) { @@ -507,7 +500,6 @@ retry: if (!pte_none(*ptep)) goto backout; - add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE); new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE) && (vma->vm_flags & VM_SHARED))); set_huge_pte_at(mm, address, ptep, new_pte); -- 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