From: Huang Ying &lt;ying.huang(a)intel.com&gt; With the advent of various new memory types, some machines will have multiple types of memory, e.g. DRAM and PMEM (persistent memory). The memory subsystem of these machines can be called memory tiering system, because the performance of the different types of memory are usually different. In such system, because of the memory accessing pattern changing etc, some pages in the slow memory may become hot globally. So in this patch, the NUMA balancing mechanism is enhanced to optimize the page placement among the different memory types according to hot/cold dynamically. In a typical memory tiering system, there are CPUs, fast memory and slow memory in each physical NUMA node. The CPUs and the fast memory will be put in one logical node (called fast memory node), while the slow memory will be put in another (faked) logical node (called slow memory node). That is, the fast memory is regarded as local while the slow memory is regarded as remote. So it's possible for the recently accessed pages in the slow memory node to be promoted to the fast memory node via the existing NUMA balancing mechanism. The original NUMA balancing mechanism will stop to migrate pages if the free memory of the target node will become below the high watermark. This is a reasonable policy if there's only one memory type. But this makes the original NUMA balancing mechanism almost not work to optimize page placement among different memory types. Details are as follows. It's the common cases that the working-set size of the workload is larger than the size of the fast memory nodes. Otherwise, it's unnecessary to use the slow memory at all. So in the common cases, there are almost always no enough free pages in the fast memory nodes, so that the globally hot pages in the slow memory node cannot be promoted to the fast memory node. To solve the issue, we have 2 choices as follows, a. Ignore the free pages watermark checking when promoting hot pages from the slow memory node to the fast memory node. This will create some memory pressure in the fast memory node, thus trigger the memory reclaiming. So that, the cold pages in the fast memory node will be demoted to the slow memory node. b. Make kswapd of the fast memory node to reclaim pages until the free pages are a little more (about 10MB) than the high watermark. Then, if the free pages of the fast memory node reaches high watermark, and some hot pages need to be promoted, kswapd of the fast memory node will be waken up to demote some cold pages in the fast memory node to the slow memory node. This will free some extra space in the fast memory node, so the hot pages in the slow memory node can be promoted to the fast memory node. The choice "a" will create the memory pressure in the fast memory node. If the memory pressure of the workload is high, the memory pressure may become so high that the memory allocation latency of the workload is influenced, e.g. the direct reclaiming may be triggered. The choice "b" works much better at this aspect. If the memory pressure of the workload is high, the hot pages promotion will stop earlier because its allocation watermark is higher than that of the normal memory allocation. So in this patch, choice "b" is implemented. In addition to the original page placement optimization among sockets, the NUMA balancing mechanism is extended to be used to optimize page placement according to hot/cold among different memory types. So the sysctl user space interface (numa_balancing) is extended in a backward compatible way as follow, so that the users can enable/disable these functionality individually. The sysctl is converted from a Boolean value to a bits field. The definition of the flags is, - 0x0: NUMA_BALANCING_DISABLED - 0x1: NUMA_BALANCING_NORMAL - 0x2: NUMA_BALANCING_MEMORY_TIERING Signed-off-by: "Huang, Ying" &lt;ying.huang(a)intel.com&gt; Cc: Andrew Morton &lt;akpm(a)linux-foundation.org&gt; Cc: Michal Hocko &lt;mhocko(a)suse.com&gt; Cc: Rik van Riel &lt;riel(a)surriel.com&gt; Cc: Mel Gorman &lt;mgorman(a)techsingularity.net&gt; Cc: Peter Zijlstra &lt;peterz(a)infradead.org&gt; Cc: Dave Hansen &lt;dave.hansen(a)linux.intel.com&gt; Cc: Yang Shi &lt;shy828301(a)gmail.com&gt; Cc: Zi Yan &lt;ziy(a)nvidia.com&gt; Cc: Wei Xu &lt;weixugc(a)google.com&gt; Cc: osalvador &lt;osalvador(a)suse.de&gt; Cc: Shakeel Butt &lt;shakeelb(a)google.com&gt; Cc: Hasan Al Maruf &lt;hasanalmaruf(a)fb.com&gt; Cc: linux-kernel(a)vger.kernel.org Cc: linux-mm(a)kvack.org Signed-off-by: zhongjiang-ali &lt;zhongjiang-ali(a)linux.alibaba.com&gt; --- Documentation/sysctl/kernel.txt | 32 ++++++++++++++++++++++---------- include/linux/sched/sysctl.h | 11 +++++++++++ kernel/sched/core.c | 21 +++++++++++++++++---- kernel/sysctl.c | 3 ++- mm/migrate.c | 19 +++++++++++++++++-- mm/vmscan.c | 16 ++++++++++++++++ 6 files changed, 85 insertions(+), 17 deletions(-) diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 37a6795..cfc38a7b 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -493,16 +493,23 @@ to the guest kernel command line (see Documentation/admin-guide/kernel-parameter numa_balancing -Enables/disables automatic page fault based NUMA memory -balancing. Memory is moved automatically to nodes -that access it often. - -Enables/disables automatic NUMA memory balancing. On NUMA machines, there -is a performance penalty if remote memory is accessed by a CPU. When this -feature is enabled the kernel samples what task thread is accessing memory -by periodically unmapping pages and later trapping a page fault. At the -time of the page fault, it is determined if the data being accessed should -be migrated to a local memory node. +Enables/disables and configure automatic page fault based NUMA memory +balancing. Memory is moved automatically to nodes that access it +often. The value to set can be the result to OR the following, + += ================================= +0x0 NUMA_BALANCING_DISABLED +0x1 NUMA_BALANCING_NORMAL +0x2 NUMA_BALANCING_MEMORY_TIERING += ================================= + +Or NUMA_BALANCING_NORMAL to optimize page placement among different +NUMA nodes to reduce remote accessing. On NUMA machines, there is a +performance penalty if remote memory is accessed by a CPU. When this +feature is enabled the kernel samples what task thread is accessing +memory by periodically unmapping pages and later trapping a page +fault. At the time of the page fault, it is determined if the data +being accessed should be migrated to a local memory node. The unmapping of pages and trapping faults incur additional overhead that ideally is offset by improved memory locality but there is no universal @@ -513,6 +520,11 @@ faults may be controlled by the numa_balancing_scan_period_min_ms, numa_balancing_scan_delay_ms, numa_balancing_scan_period_max_ms, numa_balancing_scan_size_mb, and numa_balancing_settle_count sysctls. +Or NUMA_BALANCING_MEMORY_TIERING to optimize page placement among +different types of memory (represented as different NUMA nodes) to +place the hot pages in the fast memory. This is implemented based on +unmapping and page fault too. + ============================================================== numa_balancing_scan_period_min_ms, numa_balancing_scan_delay_ms, diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index d975618b..f5e07a1 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -31,6 +31,17 @@ enum sched_tunable_scaling { SCHED_TUNABLESCALING_LINEAR, SCHED_TUNABLESCALING_END, }; + +#define NUMA_BALANCING_DISABLED 0x0 +#define NUMA_BALANCING_NORMAL 0x1 +#define NUMA_BALANCING_MEMORY_TIERING 0x2 + +#ifdef CONFIG_NUMA_BALANCING +extern int sysctl_numa_balancing_mode; +#else +#define sysctl_numa_balancing_mode 0 +#endif + extern enum sched_tunable_scaling sysctl_sched_tunable_scaling; extern unsigned int sysctl_numa_balancing_scan_delay; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fd81dd3..5b78a1a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2169,7 +2169,9 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) #ifdef CONFIG_NUMA_BALANCING -void set_numabalancing_state(bool enabled) +int sysctl_numa_balancing_mode; + +static void __set_numabalancing_state(bool enabled) { if (enabled) static_branch_enable(&sched_numa_balancing); @@ -2177,13 +2179,22 @@ void set_numabalancing_state(bool enabled) static_branch_disable(&sched_numa_balancing); } +void set_numabalancing_state(bool enabled) +{ + if (enabled) + sysctl_numa_balancing_mode = NUMA_BALANCING_NORMAL; + else + sysctl_numa_balancing_mode = NUMA_BALANCING_DISABLED; + __set_numabalancing_state(enabled); +} + #ifdef CONFIG_PROC_SYSCTL int sysctl_numa_balancing(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table t; int err; - int state = static_branch_likely(&sched_numa_balancing); + int state = sysctl_numa_balancing_mode; if (write && !capable(CAP_SYS_ADMIN)) return -EPERM; @@ -2193,8 +2204,10 @@ int sysctl_numa_balancing(struct ctl_table *table, int write, err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); if (err < 0) return err; - if (write) - set_numabalancing_state(state); + if (write) { + sysctl_numa_balancing_mode = state; + __set_numabalancing_state(state); + } return err; } #endif diff --git a/kernel/sysctl.c b/kernel/sysctl.c index ae9ccda..0420784 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -132,6 +132,7 @@ static int zero; static int __maybe_unused one = 1; static int __maybe_unused two = 2; +static int __maybe_unused three = 3; static int __maybe_unused four = 4; static unsigned long zero_ul; static unsigned long one_ul = 1; @@ -453,7 +454,7 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write, .mode = 0644, .proc_handler = sysctl_numa_balancing, .extra1 = &zero, - .extra2 = &one, + .extra2 = &three, }, #endif /* CONFIG_NUMA_BALANCING */ #endif /* CONFIG_SCHED_DEBUG */ diff --git a/mm/migrate.c b/mm/migrate.c index f86a082..5214da8 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -49,6 +49,7 @@ #include <linux/ptrace.h> #include <linux/memory.h> #include <linux/random.h> +#include <linux/sched/sysctl.h> #include <asm/tlbflush.h> @@ -1943,12 +1944,26 @@ static struct page *alloc_misplaced_dst_page(struct page *page, static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) { int page_lru; + int order = compound_order(page); - VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page); + VM_BUG_ON_PAGE(order && !PageTransHuge(page), page); /* Avoid migrating to a node that is nearly full */ - if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page))) + if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page))) { + int z; + + if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) || + !numa_demotion_enabled) + return 0; + if (next_demotion_node(pgdat->node_id) == NUMA_NO_NODE) + return 0; + for (z = pgdat->nr_zones - 1; z >= 0; z--) { + if (populated_zone(pgdat->node_zones + z)) + break; + } + wakeup_kswapd(pgdat->node_zones + z, 0, order, ZONE_MOVABLE); return 0; + } if (isolate_lru_page(page)) return 0; diff --git a/mm/vmscan.c b/mm/vmscan.c index 693fe5b..ab79a20 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -57,6 +57,7 @@ #include <linux/swapops.h> #include <linux/balloon_compaction.h> +#include <linux/sched/sysctl.h> #include "internal.h" @@ -3558,6 +3559,12 @@ static bool pgdat_watermark_boosted(pg_data_t *pgdat, int classzone_idx) } /* + * Keep the free pages on fast memory node a little more than the high + * watermark to accommodate the promoted pages. + */ +#define NUMA_BALANCING_PROMOTE_WATERMARK (10UL * 1024 * 1024 >> PAGE_SHIFT) + +/* * Returns true if there is an eligible zone balanced for the request order * and classzone_idx */ @@ -3578,6 +3585,15 @@ static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx) continue; mark = high_wmark_pages(zone); + if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && + numa_demotion_enabled && + next_demotion_node(pgdat->node_id) != NUMA_NO_NODE) { + unsigned long promote_mark; + + promote_mark = min(NUMA_BALANCING_PROMOTE_WATERMARK, + pgdat->node_present_pages >> 6); + mark += promote_mark; + } if (zone_watermark_ok_safe(zone, order, mark, classzone_idx)) return true; } -- 1.8.3.1

From: Huang Ying &lt;ying.huang(a)intel.com&gt; To optimize page placement in a memory tiering system with NUMA balancing, the hot pages in the slow memory node need to be identified. Essentially, the original NUMA balancing implementation selects the mostly recently accessed (MRU) pages as the hot pages. But this isn't a very good algorithm to identify the hot pages. So, in this patch we implemented a better hot page selection algorithm. Which is based on NUMA balancing page table scanning and hint page fault as follows, - When the page tables of the processes are scanned to change PTE/PMD to be PROT_NONE, the current time is recorded in struct page as scan time. - When the page is accessed, hint page fault will occur. The scan time is gotten from the struct page. And The hint page fault latency is defined as hint page fault time - scan time The shorter the hint page fault latency of a page is, the higher the probability of their access frequency to be higher. So the hint page fault latency is a good estimation of the page hot/cold. But it's hard to find some extra space in struct page to hold the scan time. Fortunately, we can reuse some bits used by the original NUMA balancing. NUMA balancing uses some bits in struct page to store the page accessing CPU and PID (referring to page_cpupid_xchg_last()). Which is used by the multi-stage node selection algorithm to avoid to migrate pages shared accessed by the NUMA nodes back and forth. But for pages in the slow memory node, even if they are shared accessed by multiple NUMA nodes, as long as the pages are hot, they need to be promoted to the fast memory node. So the accessing CPU and PID information are unnecessary for the slow memory pages. We can reuse these bits in struct page to record the scan time for them. For the fast memory pages, these bits are used as before. The remaining problem is how to determine the hot threshold. It's not easy to be done automatically. So we provide a sysctl knob: kernel.numa_balancing_hot_threshold_ms. All pages with hint page fault latency < the threshold will be considered hot. The system administrator can determine the hot threshold via various information, such as PMEM bandwidth limit, the average number of the pages pass the hot threshold, etc. The default hot threshold is 1 second, which works well in our performance test. The downside of the patch is that the response time to the workload hot spot changing may be much longer. For example, - A previous cold memory area becomes hot - The hint page fault will be triggered. But the hint page fault latency isn't shorter than the hot threshold. So the pages will not be promoted. - When the memory area is scanned again, maybe after a scan period, the hint page fault latency measured will be shorter than the hot threshold and the pages will be promoted. To mitigate this, - If there are enough free space in the fast memory node, the hot threshold will not be used, all pages will be promoted upon the hint page fault for fast response. - If fast response is more important for system performance, the administrator can set a higher hot threshold. Signed-off-by: "Huang, Ying" &lt;ying.huang(a)intel.com&gt; Cc: Andrew Morton &lt;akpm(a)linux-foundation.org&gt; Cc: Michal Hocko &lt;mhocko(a)suse.com&gt; Cc: Rik van Riel &lt;riel(a)surriel.com&gt; Cc: Mel Gorman &lt;mgorman(a)techsingularity.net&gt; Cc: Peter Zijlstra &lt;peterz(a)infradead.org&gt; Cc: Dave Hansen &lt;dave.hansen(a)linux.intel.com&gt; Cc: Yang Shi &lt;shy828301(a)gmail.com&gt; Cc: Zi Yan &lt;ziy(a)nvidia.com&gt; Cc: Wei Xu &lt;weixugc(a)google.com&gt; Cc: osalvador &lt;osalvador(a)suse.de&gt; Cc: Shakeel Butt &lt;shakeelb(a)google.com&gt; Cc: Hasan Al Maruf &lt;hasanalmaruf(a)fb.com&gt; Cc: linux-kernel(a)vger.kernel.org Cc: linux-mm(a)kvack.org Signed-off-by: zhongjiang-ali &lt;zhongjiang-ali(a)linux.alibaba.com&gt; --- include/linux/mm.h | 29 +++++++++++++++++++ include/linux/sched/sysctl.h | 1 + kernel/sched/fair.c | 67 ++++++++++++++++++++++++++++++++++++++++++++ kernel/sysctl.c | 7 +++++ mm/huge_memory.c | 13 +++++++-- mm/memory.c | 11 +++++++- mm/migrate.c | 12 ++++++++ mm/mmzone.c | 17 +++++++++++ mm/mprotect.c | 8 +++++- 9 files changed, 160 insertions(+), 5 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 2f9381ea..8ac6d30 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1048,6 +1048,18 @@ static inline int page_to_nid(const struct page *page) #endif #ifdef CONFIG_NUMA_BALANCING +/* page access time bits needs to hold at least 4 seconds */ +#define PAGE_ACCESS_TIME_MIN_BITS 12 +#if LAST_CPUPID_SHIFT < PAGE_ACCESS_TIME_MIN_BITS +#define PAGE_ACCESS_TIME_BUCKETS \ + (PAGE_ACCESS_TIME_MIN_BITS - LAST_CPUPID_SHIFT) +#else +#define PAGE_ACCESS_TIME_BUCKETS 0 +#endif + +#define PAGE_ACCESS_TIME_MASK \ + (LAST_CPUPID_MASK << PAGE_ACCESS_TIME_BUCKETS) + static inline int cpu_pid_to_cpupid(int cpu, int pid) { return ((cpu & LAST__CPU_MASK) << LAST__PID_SHIFT) | (pid & LAST__PID_MASK); @@ -1090,6 +1102,16 @@ static inline int page_cpupid_xchg_last(struct page *page, int cpupid) return xchg(&page->_last_cpupid, cpupid & LAST_CPUPID_MASK); } +static inline unsigned int xchg_page_access_time(struct page *page, + unsigned int time) +{ + unsigned int last_time; + + last_time = xchg(&page->_last_cpupid, + (time >> PAGE_ACCESS_TIME_BUCKETS) & LAST_CPUPID_MASK); + return last_time << PAGE_ACCESS_TIME_BUCKETS; +} + static inline int page_cpupid_last(struct page *page) { return page->_last_cpupid; @@ -1105,6 +1127,7 @@ static inline int page_cpupid_last(struct page *page) } extern int page_cpupid_xchg_last(struct page *page, int cpupid); +extern unsigned int xchg_page_access_time(struct page *page, unsigned int time); static inline void page_cpupid_reset_last(struct page *page) { @@ -1117,6 +1140,12 @@ static inline int page_cpupid_xchg_last(struct page *page, int cpupid) return page_to_nid(page); /* XXX */ } +static inline unsigned int xchg_page_access_time(struct page *page, + unsigned int time) +{ + return 0; +} + static inline int page_cpupid_last(struct page *page) { return page_to_nid(page); /* XXX */ diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index f5e07a1..6be27b6 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -38,6 +38,7 @@ enum sched_tunable_scaling { #ifdef CONFIG_NUMA_BALANCING extern int sysctl_numa_balancing_mode; +extern unsigned int sysctl_numa_balancing_hot_threshold; #else #define sysctl_numa_balancing_mode 0 #endif diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 4ad5a2c..41d6863 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2457,6 +2457,9 @@ static void update_curr_fair(struct rq *rq) /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */ unsigned int sysctl_numa_balancing_scan_delay = 1000; +/* The page with hint page fault latency < threshold in ms is considered hot */ +unsigned int sysctl_numa_balancing_hot_threshold = 1000; + struct numa_group { atomic_t refcount; @@ -2848,6 +2851,37 @@ static inline unsigned long group_weight(struct task_struct *p, int nid, return 1000 * faults / total_faults; } +static bool pgdat_free_space_enough(struct pglist_data *pgdat) +{ + int z; + unsigned long enough_mark; + + enough_mark = max(1UL * 1024 * 1024 * 1024 >> PAGE_SHIFT, + pgdat->node_present_pages >> 4); + for (z = pgdat->nr_zones - 1; z >= 0; z--) { + struct zone *zone = pgdat->node_zones + z; + + if (!populated_zone(zone)) + continue; + + if (zone_watermark_ok(zone, 0, + high_wmark_pages(zone) + enough_mark, + ZONE_MOVABLE, 0)) + return true; + } + return false; +} + +static int numa_hint_fault_latency(struct page *page) +{ + unsigned int last_time, time; + + time = jiffies_to_msecs(jiffies); + last_time = xchg_page_access_time(page, time); + + return (time - last_time) & PAGE_ACCESS_TIME_MASK; +} + bool should_numa_migrate_memory(struct task_struct *p, struct page * page, int src_nid, int dst_cpu) { @@ -2855,6 +2889,27 @@ bool should_numa_migrate_memory(struct task_struct *p, struct page * page, int dst_nid = cpu_to_node(dst_cpu); int last_cpupid, this_cpupid; + /* + * The pages in slow memory node should be migrated according + * to hot/cold instead of accessing CPU node. + */ + if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && + !node_is_toptier(src_nid)) { + struct pglist_data *pgdat; + unsigned long latency, th; + + pgdat = NODE_DATA(dst_nid); + if (pgdat_free_space_enough(pgdat)) + return true; + + th = sysctl_numa_balancing_hot_threshold; + latency = numa_hint_fault_latency(page); + if (latency > th) + return false; + + return true; + } + this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); last_cpupid = page_cpupid_xchg_last(page, this_cpupid); @@ -3873,6 +3928,11 @@ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags) if (!p->mm) return; + /* Numa faults statistics are unnecessary for the slow memory node */ + if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && + !node_is_toptier(mem_node)) + return; + /* Allocate buffer to track faults on a per-node basis */ if (unlikely(!p->numa_faults)) { int size = sizeof(*p->numa_faults) * @@ -3892,6 +3952,13 @@ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags) */ if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) { priv = 1; + } else if (unlikely(!cpu_online(cpupid_to_cpu(last_cpupid)))) { + /* + * In memory tiering mode, cpupid of slow memory page is + * used to record page access time, so its value may be + * invalid during numa balancing mode transition. + */ + return; } else { priv = cpupid_match_pid(p, last_cpupid); if (!priv && !(flags & TNF_NO_GROUP)) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 0420784..ab063be 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -456,6 +456,13 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write, .extra1 = &zero, .extra2 = &three, }, + { + .procname = "numa_balancing_hot_threshold_ms", + .data = &sysctl_numa_balancing_hot_threshold, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, #endif /* CONFIG_NUMA_BALANCING */ #endif /* CONFIG_SCHED_DEBUG */ { diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 6f11401..0a9126c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1808,7 +1808,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) struct page *page; unsigned long haddr = vmf->address & HPAGE_PMD_MASK; int page_nid = -1, this_nid = numa_node_id(); - int target_nid, last_cpupid = -1; + int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK); bool page_locked; bool migrated = false; bool was_writable; @@ -1836,7 +1836,8 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) page = pmd_page(pmd); BUG_ON(is_huge_zero_page(page)); page_nid = page_to_nid(page); - last_cpupid = page_cpupid_last(page); + if (node_is_toptier(page_nid)) + last_cpupid = page_cpupid_last(page); count_vm_numa_event(NUMA_HINT_FAULTS); if (page_nid == this_nid) { count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); @@ -2220,6 +2221,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, if (prot_numa) { struct page *page; + bool toptier; /* * Avoid trapping faults against the zero page. The read-only * data is likely to be read-cached on the local CPU and @@ -2232,13 +2234,18 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, goto unlock; page = pmd_page(*pmd); + toptier = node_is_toptier(page_to_nid(page)); /* * Skip scanning top tier node if normal numa * balancing is disabled */ if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && - node_is_toptier(page_to_nid(page))) + toptier) goto unlock; + + if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && + !toptier) + xchg_page_access_time(page, jiffies_to_msecs(jiffies)); } /* diff --git a/mm/memory.c b/mm/memory.c index 0b779c1..2100f65 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -70,6 +70,7 @@ #include <linux/dax.h> #include <linux/oom.h> #include <linux/khugepaged.h> +#include <linux/sched/sysctl.h> #include <asm/io.h> #include <asm/mmu_context.h> @@ -3928,8 +3929,16 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED)) flags |= TNF_SHARED; - last_cpupid = page_cpupid_last(page); page_nid = page_to_nid(page); + /* + * In memory tiering mode, cpupid of slow memory page is used + * to record page access time. So use default value. + */ + if ((sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && + !node_is_toptier(page_nid)) + last_cpupid = (-1 & LAST_CPUPID_MASK); + else + last_cpupid = page_cpupid_last(page); target_nid = numa_migrate_prep(page, vma, vmf->address, page_nid, &flags); pte_unmap_unlock(vmf->pte, vmf->ptl); diff --git a/mm/migrate.c b/mm/migrate.c index 5214da8..f263a4a 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -717,6 +717,18 @@ void migrate_page_states(struct page *newpage, struct page *page) * future migrations of this same page. */ cpupid = page_cpupid_xchg_last(page, -1); + /* + * If migrate between slow and fast memory node, reset cpupid, + * because that is used to record page access time in slow + * memory node + */ + if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) { + bool f_toptier = node_is_toptier(page_to_nid(page)); + bool t_toptier = node_is_toptier(page_to_nid(newpage)); + + if (f_toptier != t_toptier) + cpupid = -1; + } page_cpupid_xchg_last(newpage, cpupid); ksm_migrate_page(newpage, page); diff --git a/mm/mmzone.c b/mm/mmzone.c index 4686fdc..aa94ec7 100644 --- a/mm/mmzone.c +++ b/mm/mmzone.c @@ -112,4 +112,21 @@ int page_cpupid_xchg_last(struct page *page, int cpupid) return last_cpupid; } + +unsigned int xchg_page_access_time(struct page *page, unsigned int time) +{ + unsigned long old_flags, flags; + unsigned int last_time; + + time >>= PAGE_ACCESS_TIME_BUCKETS; + do { + old_flags = flags = page->flags; + last_time = (flags >> LAST_CPUPID_PGSHIFT) & LAST_CPUPID_MASK; + + flags &= ~(LAST_CPUPID_MASK << LAST_CPUPID_PGSHIFT); + flags |= (time & LAST_CPUPID_MASK) << LAST_CPUPID_PGSHIFT; + } while (unlikely(cmpxchg(&page->flags, old_flags, flags) != old_flags)); + + return last_time << PAGE_ACCESS_TIME_BUCKETS; +} #endif diff --git a/mm/mprotect.c b/mm/mprotect.c index fbdb09f..3072213 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -82,6 +82,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, if (prot_numa) { struct page *page; int nid; + bool toptier; page = vm_normal_page(vma, addr, oldpte); if (!page || PageKsm(page)) @@ -111,14 +112,19 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, nid = page_to_nid(page); if (target_node == nid) continue; + toptier = node_is_toptier(nid); /* * Skip scanning top tier node if normal numa * balancing is disabled */ if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && - node_is_toptier(nid)) + toptier) continue; + if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && + !toptier) + xchg_page_access_time(page, + jiffies_to_msecs(jiffies)); } ptent = ptep_modify_prot_start(mm, addr, pte); -- 1.8.3.1

From: Huang Ying &lt;ying.huang(a)intel.com&gt; It isn't easy for the administrator to determine the hot threshold. So in this patch, a method to adjust the hot threshold automatically is implemented. The basic idea is to control the number of the candidate promotion pages to match the promotion rate limit. If the hint page fault latency of a page is less than the hot threshold, we will try to promote the page, and the page is called the candidate promotion page. If the number of the candidate promotion pages in the statistics interval is much more than the promotion rate limit, the hot threshold will be decreased to reduce the number of the candidate promotion pages. Otherwise, the hot threshold will be increased to increase the number of the candidate promotion pages. To make the above method works, in each statistics interval, the total number of the pages to check (on which the hint page faults occur) and the hot/cold distribution need to be stable. Because the page tables are scanned linearly in NUMA balancing, but the hot/cold distribution isn't uniform along the address, the statistics interval should be larger than the NUMA balancing scan period. So in the patch, the max scan period is used as statistics interval and it works well in our tests. The sysctl knob kernel.numa_balancing_hot_threshold_ms becomes the initial value and max value of the hot threshold. Signed-off-by: "Huang, Ying" &lt;ying.huang(a)intel.com&gt; Cc: Andrew Morton &lt;akpm(a)linux-foundation.org&gt; Cc: Michal Hocko &lt;mhocko(a)suse.com&gt; Cc: Rik van Riel &lt;riel(a)surriel.com&gt; Cc: Mel Gorman &lt;mgorman(a)techsingularity.net&gt; Cc: Peter Zijlstra &lt;peterz(a)infradead.org&gt; Cc: Dave Hansen &lt;dave.hansen(a)linux.intel.com&gt; Cc: Yang Shi &lt;shy828301(a)gmail.com&gt; Cc: Zi Yan &lt;ziy(a)nvidia.com&gt; Cc: Wei Xu &lt;weixugc(a)google.com&gt; Cc: osalvador &lt;osalvador(a)suse.de&gt; Cc: Shakeel Butt &lt;shakeelb(a)google.com&gt; Cc: Hasan Al Maruf &lt;hasanalmaruf(a)fb.com&gt; Cc: linux-kernel(a)vger.kernel.org Cc: linux-mm(a)kvack.org Signed-off-by: zhongjiang-ali &lt;zhongjiang-ali(a)linux.alibaba.com&gt; --- include/linux/mmzone.h | 3 +++ include/linux/sched/sysctl.h | 3 +++ kernel/sched/core.c | 15 +++++++++++ kernel/sched/fair.c | 64 ++++++++++++++++++++++++++++++++++++++++---- kernel/sysctl.c | 3 ++- 5 files changed, 82 insertions(+), 6 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 4463451..fcc2c18 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -760,6 +760,9 @@ struct hugepage_reclaim { #ifdef CONFIG_NUMA_BALANCING unsigned long numa_ts; unsigned long numa_nr_candidate; + unsigned long numa_threshold_ts; + unsigned long numa_threshold_nr_candidate; + unsigned long numa_threshold; #endif /* Fields commonly accessed by the page reclaim scanner */ diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index bda72b8..ac11582 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -103,6 +103,9 @@ extern int sysctl_numa_balancing(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos); +int sysctl_numa_balancing_threshold(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos); + extern int sysctl_schedstats(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5b78a1a..2f77c69 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2189,6 +2189,18 @@ void set_numabalancing_state(bool enabled) } #ifdef CONFIG_PROC_SYSCTL +static void reset_memory_tiering(void) +{ + struct pglist_data *pgdat; + + for_each_online_pgdat(pgdat) { + pgdat->numa_threshold = 0; + pgdat->numa_threshold_nr_candidate = + node_page_state(pgdat, PGPROMOTE_CANDIDATE); + pgdat->numa_threshold_ts = jiffies; + } +} + int sysctl_numa_balancing(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { @@ -2205,6 +2217,9 @@ int sysctl_numa_balancing(struct ctl_table *table, int write, if (err < 0) return err; if (write) { + if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && + (state & NUMA_BALANCING_MEMORY_TIERING)) + reset_memory_tiering(); sysctl_numa_balancing_mode = state; __set_numabalancing_state(state); } diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e102fab..143d689 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2904,6 +2904,54 @@ static bool numa_migration_check_rate_limit(struct pglist_data *pgdat, return true; } +int sysctl_numa_balancing_threshold(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) +{ + int err; + struct pglist_data *pgdat; + + if (write && !capable(CAP_SYS_ADMIN)) + return -EPERM; + + err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (err < 0 || !write) + return err; + + for_each_online_pgdat(pgdat) + pgdat->numa_threshold = 0; + + return err; +} + +#define NUMA_MIGRATION_ADJUST_STEPS 16 + +static void numa_migration_adjust_threshold(struct pglist_data *pgdat, + unsigned long rate_limit, + unsigned long ref_th) +{ + unsigned long now = jiffies, last_th_ts, th_period; + unsigned long unit_th, th; + unsigned long nr_cand, ref_cand, diff_cand; + + th_period = msecs_to_jiffies(sysctl_numa_balancing_scan_period_max); + last_th_ts = pgdat->numa_threshold_ts; + if (now > last_th_ts + th_period && + cmpxchg(&pgdat->numa_threshold_ts, last_th_ts, now) == last_th_ts) { + ref_cand = rate_limit * + sysctl_numa_balancing_scan_period_max / 1000; + nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE); + diff_cand = nr_cand - pgdat->numa_threshold_nr_candidate; + unit_th = ref_th / NUMA_MIGRATION_ADJUST_STEPS; + th = pgdat->numa_threshold ? : ref_th; + if (diff_cand > ref_cand * 11 / 10) + th = max(th - unit_th, unit_th); + else if (diff_cand < ref_cand * 9 / 10) + th = min(th + unit_th, ref_th); + pgdat->numa_threshold_nr_candidate = nr_cand; + pgdat->numa_threshold = th; + } +} + bool should_numa_migrate_memory(struct task_struct *p, struct page * page, int src_nid, int dst_cpu) { @@ -2918,19 +2966,25 @@ bool should_numa_migrate_memory(struct task_struct *p, struct page * page, if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && !node_is_toptier(src_nid)) { struct pglist_data *pgdat; - unsigned long rate_limit, latency, th; + unsigned long rate_limit, latency, th, def_th; pgdat = NODE_DATA(dst_nid); - if (pgdat_free_space_enough(pgdat)) + if (pgdat_free_space_enough(pgdat)) { + /* workload changed, reset hot threshold */ + pgdat->numa_threshold = 0; return true; + } + + def_th = sysctl_numa_balancing_hot_threshold; + rate_limit = + sysctl_numa_balancing_rate_limit << (20 - PAGE_SHIFT); + numa_migration_adjust_threshold(pgdat, rate_limit, def_th); - th = sysctl_numa_balancing_hot_threshold; + th = pgdat->numa_threshold ? : def_th; latency = numa_hint_fault_latency(page); if (latency > th) return false; - rate_limit = - sysctl_numa_balancing_rate_limit << (20 - PAGE_SHIFT); return numa_migration_check_rate_limit(pgdat, rate_limit, 1UL << compound_order(page)); } diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 32e8218..0fe1ea1 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -461,7 +461,8 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write, .data = &sysctl_numa_balancing_hot_threshold, .maxlen = sizeof(unsigned int), .mode = 0644, - .proc_handler = proc_dointvec, + .proc_handler = sysctl_numa_balancing_threshold, + .extra1 = &zero, }, { .procname = "numa_balancing_rate_limit_mbps", -- 1.8.3.1