On Fri, 2012-12-07 at 10:23 +0000, Mel Gorman wrote: > It is tricky to quantify the basic cost of automatic NUMA placement in a > meaningful manner. This patch adds some vmstats that can be used as part > of a basic costing model.
Hi Gorman, > > u = basic unit = sizeof(void *) > Ca = cost of struct page access = sizeof(struct page) / u > Cpte = Cost PTE access = Ca > Cupdate = Cost PTE update = (2 * Cpte) + (2 * Wlock) > where Cpte is incurred twice for a read and a write and Wlock > is a constant representing the cost of taking or releasing a > lock > Cnumahint = Cost of a minor page fault = some high constant e.g. 1000 > Cpagerw = Cost to read or write a full page = Ca + PAGE_SIZE/u Why cpagerw = Ca + PAGE_SIZE/u instead of Cpte + PAGE_SIZE/u ? > Ci = Cost of page isolation = Ca + Wi > where Wi is a constant that should reflect the approximate cost > of the locking operation > Cpagecopy = Cpagerw + (Cpagerw * Wnuma) + Ci + (Ci * Wnuma) > where Wnuma is the approximate NUMA factor. 1 is local. 1.2 > would imply that remote accesses are 20% more expensive > > Balancing cost = Cpte * numa_pte_updates + > Cnumahint * numa_hint_faults + > Ci * numa_pages_migrated + > Cpagecopy * numa_pages_migrated > Since Cpagecopy has already accumulated ci why count ci twice ? > Note that numa_pages_migrated is used as a measure of how many pages > were isolated even though it would miss pages that failed to migrate. A > vmstat counter could have been added for it but the isolation cost is > pretty marginal in comparison to the overall cost so it seemed overkill. > > The ideal way to measure automatic placement benefit would be to count > the number of remote accesses versus local accesses and do something like > > benefit = (remote_accesses_before - remove_access_after) * Wnuma > > but the information is not readily available. As a workload converges, the > expection would be that the number of remote numa hints would reduce to 0. > > convergence = numa_hint_faults_local / numa_hint_faults > where this is measured for the last N number of > numa hints recorded. When the workload is fully > converged the value is 1. > convergence tend to 0 is better or 1 is better? If tend to 1, Cpte * numa_pte_updates + Cnumahint * numa_hint_faults are just waste, where I miss? > This can measure if the placement policy is converging and how fast it is > doing it. > > Signed-off-by: Mel Gorman <[email protected]> > Acked-by: Rik van Riel <[email protected]> > --- > include/linux/vm_event_item.h | 6 ++++++ > include/linux/vmstat.h | 8 ++++++++ > mm/huge_memory.c | 5 +++++ > mm/memory.c | 12 ++++++++++++ > mm/mempolicy.c | 2 ++ > mm/migrate.c | 3 ++- > mm/vmstat.c | 6 ++++++ > 7 files changed, 41 insertions(+), 1 deletion(-) > > diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h > index a1f750b..dded0af 100644 > --- a/include/linux/vm_event_item.h > +++ b/include/linux/vm_event_item.h > @@ -38,6 +38,12 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, > KSWAPD_LOW_WMARK_HIT_QUICKLY, KSWAPD_HIGH_WMARK_HIT_QUICKLY, > KSWAPD_SKIP_CONGESTION_WAIT, > PAGEOUTRUN, ALLOCSTALL, PGROTATED, > +#ifdef CONFIG_BALANCE_NUMA > + NUMA_PTE_UPDATES, > + NUMA_HINT_FAULTS, > + NUMA_HINT_FAULTS_LOCAL, > + NUMA_PAGE_MIGRATE, > +#endif > #ifdef CONFIG_MIGRATION > PGMIGRATE_SUCCESS, PGMIGRATE_FAIL, > #endif > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h > index 92a86b2..dffccfa 100644 > --- a/include/linux/vmstat.h > +++ b/include/linux/vmstat.h > @@ -80,6 +80,14 @@ static inline void vm_events_fold_cpu(int cpu) > > #endif /* CONFIG_VM_EVENT_COUNTERS */ > > +#ifdef CONFIG_BALANCE_NUMA > +#define count_vm_numa_event(x) count_vm_event(x) > +#define count_vm_numa_events(x, y) count_vm_events(x, y) > +#else > +#define count_vm_numa_event(x) do {} while (0) > +#define count_vm_numa_events(x, y) do {} while (0) > +#endif /* CONFIG_BALANCE_NUMA */ > + > #define __count_zone_vm_events(item, zone, delta) \ > __count_vm_events(item##_NORMAL - ZONE_NORMAL + \ > zone_idx(zone), delta) > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index b3d4c4b..66e73cc 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1025,6 +1025,7 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct > vm_area_struct *vma, > struct page *page = NULL; > unsigned long haddr = addr & HPAGE_PMD_MASK; > int target_nid; > + int current_nid = -1; > > spin_lock(&mm->page_table_lock); > if (unlikely(!pmd_same(pmd, *pmdp))) > @@ -1033,6 +1034,10 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct > vm_area_struct *vma, > page = pmd_page(pmd); > get_page(page); > spin_unlock(&mm->page_table_lock); > + current_nid = page_to_nid(page); > + count_vm_numa_event(NUMA_HINT_FAULTS); > + if (current_nid == numa_node_id()) > + count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); > > target_nid = mpol_misplaced(page, vma, haddr); > if (target_nid == -1) > diff --git a/mm/memory.c b/mm/memory.c > index 1d6f85a..47f5dd1 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3477,6 +3477,7 @@ int do_numa_page(struct mm_struct *mm, struct > vm_area_struct *vma, > set_pte_at(mm, addr, ptep, pte); > update_mmu_cache(vma, addr, ptep); > > + count_vm_numa_event(NUMA_HINT_FAULTS); > page = vm_normal_page(vma, addr, pte); > if (!page) { > pte_unmap_unlock(ptep, ptl); > @@ -3485,6 +3486,8 @@ int do_numa_page(struct mm_struct *mm, struct > vm_area_struct *vma, > > get_page(page); > current_nid = page_to_nid(page); > + if (current_nid == numa_node_id()) > + count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); > target_nid = mpol_misplaced(page, vma, addr); > pte_unmap_unlock(ptep, ptl); > if (target_nid == -1) { > @@ -3517,6 +3520,9 @@ static int do_pmd_numa_page(struct mm_struct *mm, > struct vm_area_struct *vma, > unsigned long offset; > spinlock_t *ptl; > bool numa = false; > + int local_nid = numa_node_id(); > + unsigned long nr_faults = 0; > + unsigned long nr_faults_local = 0; > > spin_lock(&mm->page_table_lock); > pmd = *pmdp; > @@ -3565,10 +3571,16 @@ static int do_pmd_numa_page(struct mm_struct *mm, > struct vm_area_struct *vma, > curr_nid = page_to_nid(page); > task_numa_fault(curr_nid, 1); > > + nr_faults++; > + if (curr_nid == local_nid) > + nr_faults_local++; > + > pte = pte_offset_map_lock(mm, pmdp, addr, &ptl); > } > pte_unmap_unlock(orig_pte, ptl); > > + count_vm_numa_events(NUMA_HINT_FAULTS, nr_faults); > + count_vm_numa_events(NUMA_HINT_FAULTS_LOCAL, nr_faults_local); > return 0; > } > #else > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index a7a62fe..516491f 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -583,6 +583,8 @@ unsigned long change_prot_numa(struct vm_area_struct *vma, > BUILD_BUG_ON(_PAGE_NUMA != _PAGE_PROTNONE); > > nr_updated = change_protection(vma, addr, end, vma->vm_page_prot, 0, 1); > + if (nr_updated) > + count_vm_numa_events(NUMA_PTE_UPDATES, nr_updated); > > return nr_updated; > } > diff --git a/mm/migrate.c b/mm/migrate.c > index 49878d7..4f55694 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1514,7 +1514,8 @@ int migrate_misplaced_page(struct page *page, int node) > if (nr_remaining) { > putback_lru_pages(&migratepages); > isolated = 0; > - } > + } else > + count_vm_numa_event(NUMA_PAGE_MIGRATE); > } > BUG_ON(!list_empty(&migratepages)); > out: > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 3a067fa..cfa386da 100644 > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -774,6 +774,12 @@ const char * const vmstat_text[] = { > > "pgrotated", > > +#ifdef CONFIG_BALANCE_NUMA > + "numa_pte_updates", > + "numa_hint_faults", > + "numa_hint_faults_local", > + "numa_pages_migrated", > +#endif > #ifdef CONFIG_MIGRATION > "pgmigrate_success", > "pgmigrate_fail", -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
