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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/memory.c
parent861f2fb8e796022b4928cab9c74fca6681a1c557 (diff)
downloadop-kernel-dev-365e9c87a982c03d0af3886e29d877f581b59611.zip
op-kernel-dev-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/memory.c')
-rw-r--r--mm/memory.c17
1 files changed, 1 insertions, 16 deletions
diff --git a/mm/memory.c b/mm/memory.c
index a25ee1d..692ad81 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)
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