From efaffc5e40aeced0bcb497ed7a0a5b8c14abfcdf Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Mon, 1 Oct 2018 11:05:24 +0100 Subject: mm, sched/numa: Remove rate-limiting of automatic NUMA balancing migration Rate limiting of page migrations due to automatic NUMA balancing was introduced to mitigate the worst-case scenario of migrating at high frequency due to false sharing or slowly ping-ponging between nodes. Since then, a lot of effort was spent on correctly identifying these pages and avoiding unnecessary migrations and the safety net may no longer be required. Jirka Hladky reported a regression in 4.17 due to a scheduler patch that avoids spreading STREAM tasks wide prematurely. However, once the task was properly placed, it delayed migrating the memory due to rate limiting. Increasing the limit fixed the problem for him. Currently, the limit is hard-coded and does not account for the real capabilities of the hardware. Even if an estimate was attempted, it would not properly account for the number of memory controllers and it could not account for the amount of bandwidth used for normal accesses. Rather than fudging, this patch simply eliminates the rate limiting. However, Jirka reports that a STREAM configuration using multiple processes achieved similar performance to 4.16. In local tests, this patch improved performance of STREAM relative to the baseline but it is somewhat machine-dependent. Most workloads show little or not performance difference implying that there is not a heavily reliance on the throttling mechanism and it is safe to remove. STREAM on 2-socket machine 4.19.0-rc5 4.19.0-rc5 numab-v1r1 noratelimit-v1r1 MB/sec copy 43298.52 ( 0.00%) 44673.38 ( 3.18%) MB/sec scale 30115.06 ( 0.00%) 31293.06 ( 3.91%) MB/sec add 32825.12 ( 0.00%) 34883.62 ( 6.27%) MB/sec triad 32549.52 ( 0.00%) 34906.60 ( 7.24% Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel Acked-by: Peter Zijlstra Cc: Jirka Hladky Cc: Linus Torvalds Cc: Linux-MM Cc: Srikar Dronamraju Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20181001100525.29789-2-mgorman@techsingularity.net Signed-off-by: Ingo Molnar --- mm/page_alloc.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 89d2a2ab3fe6..706a738c0aee 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6197,8 +6197,6 @@ static unsigned long __init calc_memmap_size(unsigned long spanned_pages, static void pgdat_init_numabalancing(struct pglist_data *pgdat) { spin_lock_init(&pgdat->numabalancing_migrate_lock); - pgdat->numabalancing_migrate_nr_pages = 0; - pgdat->numabalancing_migrate_next_window = jiffies; } #else static void pgdat_init_numabalancing(struct pglist_data *pgdat) {} -- cgit v1.2.3 From e054637597ba36d3729ba6a3a3dd7aad8e2a3003 Mon Sep 17 00:00:00 2001 From: Srikar Dronamraju Date: Sat, 6 Oct 2018 16:53:19 +0530 Subject: mm, sched/numa: Remove remaining traces of NUMA rate-limiting Remove the leftover pglist_data::numabalancing_migrate_lock and its initialization, we stopped using this lock with: efaffc5e40ae ("mm, sched/numa: Remove rate-limiting of automatic NUMA balancing migration") [ mingo: Rewrote the changelog. ] Signed-off-by: Srikar Dronamraju Acked-by: Mel Gorman Cc: Linus Torvalds Cc: Linux-MM Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1538824999-31230-1-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- include/linux/mmzone.h | 4 ---- mm/page_alloc.c | 10 ---------- 2 files changed, 14 deletions(-) (limited to 'mm/page_alloc.c') diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 3f4c0b167333..d4b0c79d2924 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -667,10 +667,6 @@ typedef struct pglist_data { enum zone_type kcompactd_classzone_idx; wait_queue_head_t kcompactd_wait; struct task_struct *kcompactd; -#endif -#ifdef CONFIG_NUMA_BALANCING - /* Lock serializing the migrate rate limiting window */ - spinlock_t numabalancing_migrate_lock; #endif /* * This is a per-node reserve of pages that are not available diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 706a738c0aee..e2ef1c17942f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6193,15 +6193,6 @@ static unsigned long __init calc_memmap_size(unsigned long spanned_pages, return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT; } -#ifdef CONFIG_NUMA_BALANCING -static void pgdat_init_numabalancing(struct pglist_data *pgdat) -{ - spin_lock_init(&pgdat->numabalancing_migrate_lock); -} -#else -static void pgdat_init_numabalancing(struct pglist_data *pgdat) {} -#endif - #ifdef CONFIG_TRANSPARENT_HUGEPAGE static void pgdat_init_split_queue(struct pglist_data *pgdat) { @@ -6226,7 +6217,6 @@ static void __meminit pgdat_init_internals(struct pglist_data *pgdat) { pgdat_resize_init(pgdat); - pgdat_init_numabalancing(pgdat); pgdat_init_split_queue(pgdat); pgdat_init_kcompactd(pgdat); -- cgit v1.2.3