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authorChen, Kenneth W <kenneth.w.chen@intel.com>2006-12-06 23:32:07 -0500
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-07 11:39:21 -0500
commitcace673d376d97b0c66ffa0a49b8d588a696d5d2 (patch)
treec85c2ad65ad10132f00b484e91c8bfcd6e3f1afc /mm
parent39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa (diff)
[PATCH] htlb forget rss with pt sharing
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. Hugetlb page are special, they are reserved up front in global reservation pool and is not reclaimable. From physical memory resource point of view, it is already consumed regardless whether there are users using them. If the concern is that RSS can be used to control resource allocation, we already can specify hugetlb fs size limit and sysadmin can enforce that at mount time. Combined with the two points mentioned above, I fail to see if there is anything got affected because of this patch. Signed-off-by: Ken Chen <kenneth.w.chen@intel.com> Acked-by: Hugh Dickins <hugh@veritas.com> Cc: Dave McCracken <dmccr@us.ibm.com> Cc: William Lee Irwin III <wli@holomorphy.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Gibson <david@gibson.dropbear.id.au> Cc: Adam Litke <agl@us.ibm.com> Cc: Paul Mundt <lethal@linux-sh.org> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/hugetlb.c8
1 files changed, 0 insertions, 8 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9244971b679..2911a364481 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -344,7 +344,6 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
344 entry = *src_pte; 344 entry = *src_pte;
345 ptepage = pte_page(entry); 345 ptepage = pte_page(entry);
346 get_page(ptepage); 346 get_page(ptepage);
347 add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
348 set_huge_pte_at(dst, addr, dst_pte, entry); 347 set_huge_pte_at(dst, addr, dst_pte, entry);
349 } 348 }
350 spin_unlock(&src->page_table_lock); 349 spin_unlock(&src->page_table_lock);
@@ -377,10 +376,6 @@ void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
377 BUG_ON(end & ~HPAGE_MASK); 376 BUG_ON(end & ~HPAGE_MASK);
378 377
379 spin_lock(&mm->page_table_lock); 378 spin_lock(&mm->page_table_lock);
380
381 /* Update high watermark before we lower rss */
382 update_hiwater_rss(mm);
383
384 for (address = start; address < end; address += HPAGE_SIZE) { 379 for (address = start; address < end; address += HPAGE_SIZE) {
385 ptep = huge_pte_offset(mm, address); 380 ptep = huge_pte_offset(mm, address);
386 if (!ptep) 381 if (!ptep)
@@ -395,9 +390,7 @@ void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
395 390
396 page = pte_page(pte); 391 page = pte_page(pte);
397 list_add(&page->lru, &page_list); 392 list_add(&page->lru, &page_list);
398 add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
399 } 393 }
400
401 spin_unlock(&mm->page_table_lock); 394 spin_unlock(&mm->page_table_lock);
402 flush_tlb_range(vma, start, end); 395 flush_tlb_range(vma, start, end);
403 list_for_each_entry_safe(page, tmp, &page_list, lru) { 396 list_for_each_entry_safe(page, tmp, &page_list, lru) {
@@ -523,7 +516,6 @@ retry:
523 if (!pte_none(*ptep)) 516 if (!pte_none(*ptep))
524 goto backout; 517 goto backout;
525 518
526 add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
527 new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE) 519 new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
528 && (vma->vm_flags & VM_SHARED))); 520 && (vma->vm_flags & VM_SHARED)));
529 set_huge_pte_at(mm, address, ptep, new_pte); 521 set_huge_pte_at(mm, address, ptep, new_pte);