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authorHugh Dickins <hugh@veritas.com>2005-10-29 18:16:18 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-29 21:40:39 -0700
commit365e9c87a982c03d0af3886e29d877f581b59611 (patch)
treed06c1918ca9fe6677d7e4e869555e095004274f7 /mm
parent861f2fb8e796022b4928cab9c74fca6681a1c557 (diff)
downloadlinux-linaro-365e9c87a982c03d0af3886e29d877f581b59611.tar.gz
[PATCH] mm: update_hiwaters just in time
update_mem_hiwater has attracted various criticisms, in particular from those concerned with mm scalability. Originally it was called whenever rss or total_vm got raised. Then many of those callsites were replaced by a timer tick call from account_system_time. Now Frank van Maarseveen reports that to be found inadequate. How about this? Works for Frank. Replace update_mem_hiwater, a poor combination of two unrelated ops, by macros update_hiwater_rss and update_hiwater_vm. Don't attempt to keep mm->hiwater_rss up to date at timer tick, nor every time we raise rss (usually by 1): those are hot paths. Do the opposite, update only when about to lower rss (usually by many), or just before final accounting in do_exit. Handle mm->hiwater_vm in the same way, though it's much less of an issue. Demand that whoever collects these hiwater statistics do the work of taking the maximum with rss or total_vm. And there has been no collector of these hiwater statistics in the tree. The new convention needs an example, so match Frank's usage by adding a VmPeak line above VmSize to /proc/<pid>/status, and also a VmHWM line above VmRSS (High-Water-Mark or High-Water-Memory). There was a particular anomaly during mremap move, that hiwater_vm might be captured too high. A fleeting such anomaly remains, but it's quickly corrected now, whereas before it would stick. What locking? None: if the app is racy then these statistics will be racy, it's not worth any overhead to make them exact. But whenever it suits, hiwater_vm is updated under exclusive mmap_sem, and hiwater_rss under page_table_lock (for now) or with preemption disabled (later on): without going to any trouble, minimize the time between reading current values and updating, to minimize those occasions when a racing thread bumps a count up and back down in between. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/fremap.c4
-rw-r--r--mm/hugetlb.c3
-rw-r--r--mm/memory.c17
-rw-r--r--mm/mmap.c4
-rw-r--r--mm/mremap.c12
-rw-r--r--mm/nommu.c15
-rw-r--r--mm/rmap.c6
7 files changed, 29 insertions, 32 deletions
diff --git a/mm/fremap.c b/mm/fremap.c
index 7f08d10ceaf..49719a35769 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -143,8 +143,10 @@ int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
if (!pte)
goto err_unlock;
- if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte))
+ if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) {
+ update_hiwater_rss(mm);
dec_mm_counter(mm, file_rss);
+ }
set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
pte_val = *pte;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 094455bcbbf..ac5f044bf51 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -310,6 +310,9 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
BUG_ON(start & ~HPAGE_MASK);
BUG_ON(end & ~HPAGE_MASK);
+ /* 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)
diff --git a/mm/memory.c b/mm/memory.c
index a25ee1d3e20..692ad810263 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -820,6 +820,7 @@ unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
lru_add_drain();
spin_lock(&mm->page_table_lock);
tlb = tlb_gather_mmu(mm, 0);
+ update_hiwater_rss(mm);
end = unmap_vmas(&tlb, mm, vma, address, end, &nr_accounted, details);
tlb_finish_mmu(tlb, address, end);
spin_unlock(&mm->page_table_lock);
@@ -2225,22 +2226,6 @@ unsigned long vmalloc_to_pfn(void * vmalloc_addr)
EXPORT_SYMBOL(vmalloc_to_pfn);
-/*
- * update_mem_hiwater
- * - update per process rss and vm high water data
- */
-void update_mem_hiwater(struct task_struct *tsk)
-{
- if (tsk->mm) {
- unsigned long rss = get_mm_rss(tsk->mm);
-
- if (tsk->mm->hiwater_rss < rss)
- tsk->mm->hiwater_rss = rss;
- if (tsk->mm->hiwater_vm < tsk->mm->total_vm)
- tsk->mm->hiwater_vm = tsk->mm->total_vm;
- }
-}
-
#if !defined(__HAVE_ARCH_GATE_AREA)
#if defined(AT_SYSINFO_EHDR)
diff --git a/mm/mmap.c b/mm/mmap.c
index 8a111792b8d..c43b2845700 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1640,6 +1640,8 @@ find_extend_vma(struct mm_struct * mm, unsigned long addr)
*/
static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
{
+ /* Update high watermark before we lower total_vm */
+ update_hiwater_vm(mm);
do {
long nrpages = vma_pages(vma);
@@ -1668,6 +1670,7 @@ static void unmap_region(struct mm_struct *mm,
lru_add_drain();
spin_lock(&mm->page_table_lock);
tlb = tlb_gather_mmu(mm, 0);
+ update_hiwater_rss(mm);
unmap_vmas(&tlb, mm, vma, start, end, &nr_accounted, NULL);
vm_unacct_memory(nr_accounted);
free_pgtables(&tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
@@ -1953,6 +1956,7 @@ void exit_mmap(struct mm_struct *mm)
flush_cache_mm(mm);
tlb = tlb_gather_mmu(mm, 1);
+ /* Don't update_hiwater_rss(mm) here, do_exit already did */
/* Use -1 here to ensure all VMAs in the mm are unmapped */
end = unmap_vmas(&tlb, mm, vma, 0, -1, &nr_accounted, NULL);
vm_unacct_memory(nr_accounted);
diff --git a/mm/mremap.c b/mm/mremap.c
index 318eea5467a..ccf45647702 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -167,6 +167,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
unsigned long new_pgoff;
unsigned long moved_len;
unsigned long excess = 0;
+ unsigned long hiwater_vm;
int split = 0;
/*
@@ -205,9 +206,15 @@ static unsigned long move_vma(struct vm_area_struct *vma,
}
/*
- * if we failed to move page tables we still do total_vm increment
- * since do_munmap() will decrement it by old_len == new_len
+ * If we failed to move page tables we still do total_vm increment
+ * since do_munmap() will decrement it by old_len == new_len.
+ *
+ * Since total_vm is about to be raised artificially high for a
+ * moment, we need to restore high watermark afterwards: if stats
+ * are taken meanwhile, total_vm and hiwater_vm appear too high.
+ * If this were a serious issue, we'd add a flag to do_munmap().
*/
+ hiwater_vm = mm->hiwater_vm;
mm->total_vm += new_len >> PAGE_SHIFT;
vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
@@ -216,6 +223,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
vm_unacct_memory(excess >> PAGE_SHIFT);
excess = 0;
}
+ mm->hiwater_vm = hiwater_vm;
/* Restore VM_ACCOUNT if one or two pieces of vma left */
if (excess) {
diff --git a/mm/nommu.c b/mm/nommu.c
index 599924886eb..dfb124ffb9b 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -931,6 +931,8 @@ int do_munmap(struct mm_struct *mm, unsigned long addr, size_t len)
realalloc -= kobjsize(vml);
askedalloc -= sizeof(*vml);
kfree(vml);
+
+ update_hiwater_vm(mm);
mm->total_vm -= len >> PAGE_SHIFT;
#ifdef DEBUG
@@ -1078,19 +1080,6 @@ void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
{
}
-void update_mem_hiwater(struct task_struct *tsk)
-{
- unsigned long rss;
-
- if (likely(tsk->mm)) {
- rss = get_mm_rss(tsk->mm);
- if (tsk->mm->hiwater_rss < rss)
- tsk->mm->hiwater_rss = rss;
- if (tsk->mm->hiwater_vm < tsk->mm->total_vm)
- tsk->mm->hiwater_vm = tsk->mm->total_vm;
- }
-}
-
void unmap_mapping_range(struct address_space *mapping,
loff_t const holebegin, loff_t const holelen,
int even_cows)
diff --git a/mm/rmap.c b/mm/rmap.c
index f69d5342ce7..4c52c56c990 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -538,6 +538,9 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
if (pte_dirty(pteval))
set_page_dirty(page);
+ /* Update high watermark before we lower rss */
+ update_hiwater_rss(mm);
+
if (PageAnon(page)) {
swp_entry_t entry = { .val = page->private };
/*
@@ -628,6 +631,9 @@ static void try_to_unmap_cluster(unsigned long cursor,
if (!pmd_present(*pmd))
goto out_unlock;
+ /* Update high watermark before we lower rss */
+ update_hiwater_rss(mm);
+
for (original_pte = pte = pte_offset_map(pmd, address);
address < end; pte++, address += PAGE_SIZE) {