| Message ID | 20211116013522.140575-3-ying.huang@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | NUMA balancing: optimize memory placement for memory tiering system | expand |
On 15 Nov 2021, at 20:35, Huang Ying wrote: > 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. Why 10MB? Is 10MB big enough to avoid creating memory pressure on fast memory? This number seems pretty ad-hoc and may only work well on your test machine. In theory, this extra free memory space should be related to page promotion throughput and kswapd demotion throughput, right? Patch 5 allows user to adjust page promotion throughput, NUMA_BALANCING_PROMOTE_WATERMARK at least can be something like X * numa_balancing_rate_limit_mbps. Also, is there any way of measuring kswapd demotion throughput at boot time? So we can take it into account too. Does this make sense? > > 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" <ying.huang@intel.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Rik van Riel <riel@surriel.com> > Cc: Mel Gorman <mgorman@suse.de> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Yang Shi <shy828301@gmail.com> > Cc: Zi Yan <ziy@nvidia.com> > Cc: Wei Xu <weixugc@google.com> > Cc: osalvador <osalvador@suse.de> > Cc: Shakeel Butt <shakeelb@google.com> > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > --- > Documentation/admin-guide/sysctl/kernel.rst | 29 ++++++++++++++------- > include/linux/sched/sysctl.h | 10 +++++++ > kernel/sched/core.c | 21 ++++++++++++--- > kernel/sysctl.c | 3 ++- > mm/migrate.c | 19 ++++++++++++-- > mm/vmscan.c | 16 ++++++++++++ > 6 files changed, 82 insertions(+), 16 deletions(-) > > diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst > index 426162009ce9..1974a559c10b 100644 > --- a/Documentation/admin-guide/sysctl/kernel.rst > +++ b/Documentation/admin-guide/sysctl/kernel.rst > @@ -595,16 +595,23 @@ Documentation/admin-guide/kernel-parameters.rst). > numa_balancing > ============== > > -Enables/disables automatic page fault based NUMA memory > -balancing. Memory is moved automatically to nodes > -that access it often. > +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, > > -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. > += ================================= > +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 > @@ -615,6 +622,10 @@ 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, numa_balancing_scan_period_max_ms, numa_balancing_scan_size_mb > =============================================================================================================================== > diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h > index 304f431178fd..bc54c1d75d6d 100644 > --- a/include/linux/sched/sysctl.h > +++ b/include/linux/sched/sysctl.h > @@ -35,6 +35,16 @@ enum sched_tunable_scaling { > 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 > + > /* > * control realtime throttling: > * > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 3c9b0fda64ac..5dcabc98432f 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -4265,7 +4265,9 @@ DEFINE_STATIC_KEY_FALSE(sched_numa_balancing); > > #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); > @@ -4273,13 +4275,22 @@ 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 *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; > @@ -4289,8 +4300,10 @@ 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 083be6af29d7..a1be94ea80ba 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -115,6 +115,7 @@ static int sixty = 60; > > static int __maybe_unused neg_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; > @@ -1808,7 +1809,7 @@ static struct ctl_table kern_table[] = { > .mode = 0644, > .proc_handler = sysctl_numa_balancing, > .extra1 = SYSCTL_ZERO, > - .extra2 = SYSCTL_ONE, > + .extra2 = &three, > }, > #endif /* CONFIG_NUMA_BALANCING */ > { > diff --git a/mm/migrate.c b/mm/migrate.c > index b7c27abb0e5c..286c84c014dd 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -50,6 +50,7 @@ > #include <linux/ptrace.h> > #include <linux/oom.h> > #include <linux/memory.h> > +#include <linux/sched/sysctl.h> > > #include <asm/tlbflush.h> > > @@ -2103,16 +2104,30 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) > { > int page_lru; > int nr_pages = thp_nr_pages(page); > + int order = compound_order(page); > > - VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page); > + VM_BUG_ON_PAGE(order && !PageTransHuge(page), page); > > /* Do not migrate THP mapped by multiple processes */ > if (PageTransHuge(page) && total_mapcount(page) > 1) > return 0; > > /* Avoid migrating to a node that is nearly full */ > - if (!migrate_balanced_pgdat(pgdat, nr_pages)) > + if (!migrate_balanced_pgdat(pgdat, nr_pages)) { > + 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 fb9584641ac7..8ec955404bd1 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -56,6 +56,7 @@ > > #include <linux/swapops.h> > #include <linux/balloon_compaction.h> > +#include <linux/sched/sysctl.h> > > #include "internal.h" > > @@ -3908,6 +3909,12 @@ static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx) > return false; > } > > +/* > + * 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 highest_zoneidx > @@ -3929,6 +3936,15 @@ static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx) > 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, highest_zoneidx)) > return true; > } > -- > 2.30.2 -- Best Regards, Yan, Zi
Hi, Zi, Thanks for review! Zi Yan <ziy@nvidia.com> writes: > On 15 Nov 2021, at 20:35, Huang Ying wrote: > >> 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. > > Why 10MB? Is 10MB big enough to avoid creating memory pressure on fast > memory? This number seems pretty ad-hoc and may only work well on your > test machine. > > In theory, this extra free memory space should be related to page promotion > throughput and kswapd demotion throughput, right? Patch 5 allows user > to adjust page promotion throughput, NUMA_BALANCING_PROMOTE_WATERMARK > at least can be something like X * numa_balancing_rate_limit_mbps. > Also, is there any way of measuring kswapd demotion throughput at boot > time? So we can take it into account too. Does this make sense? Yes. 10MB is just a ad-hoc number that happens work well on my test machine. And I am glad to discuss the proper value. - The effect of the patchset will keep the size of the free memory in the DRAM node between HIGH_WATERMARK and HIGH_WATERMARK + PROMOTE_WATERMARK in normal cases. So PROMOTE_WATERMARK should be as small as possible to take full advantage of the valuable DRAM. - The PROMOTE_WATERMARK should be larger than the max per-CPU counter error. So that migrate_balanced_pgdat() for promotion and pgdat_balanced() for demotion can cooperate. - The PROMOTE_WATERMARK should be large enough to batch the demotion. - If the promotion speed is slower than the demotion speed, the larger the PROMOTE_WATERMARK, the longer the sleep time of kswapd. If the promotion speed is faster than the demotion speed, kswapd will keep running until promotion is rate limited at least. So, if we set PROMOTE_WATERMARK as N * numa_balancing_rate_limit_mbps, then kswapd will sleep about N seconds after the number of the free pages reaches PROMOTE_WATERMARK. Is that expected? All in all, I don't think some ad-hoc number such as 10MB is good enough. And the solution adopted in this patch should be as simple as possible. This will provide a baseline, so that we can improve it later with more sophisticated solution with the numbers. Do you agree? Best Regards, Huang, Ying >> >> 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" <ying.huang@intel.com> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Michal Hocko <mhocko@suse.com> >> Cc: Rik van Riel <riel@surriel.com> >> Cc: Mel Gorman <mgorman@suse.de> >> Cc: Peter Zijlstra <peterz@infradead.org> >> Cc: Dave Hansen <dave.hansen@linux.intel.com> >> Cc: Yang Shi <shy828301@gmail.com> >> Cc: Zi Yan <ziy@nvidia.com> >> Cc: Wei Xu <weixugc@google.com> >> Cc: osalvador <osalvador@suse.de> >> Cc: Shakeel Butt <shakeelb@google.com> >> Cc: linux-kernel@vger.kernel.org >> Cc: linux-mm@kvack.org [snip] Best Regards, Huang, Ying
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index 426162009ce9..1974a559c10b 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -595,16 +595,23 @@ Documentation/admin-guide/kernel-parameters.rst). numa_balancing ============== -Enables/disables automatic page fault based NUMA memory -balancing. Memory is moved automatically to nodes -that access it often. +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, -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. += ================================= +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 @@ -615,6 +622,10 @@ 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, numa_balancing_scan_period_max_ms, numa_balancing_scan_size_mb =============================================================================================================================== diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index 304f431178fd..bc54c1d75d6d 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -35,6 +35,16 @@ enum sched_tunable_scaling { 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 + /* * control realtime throttling: * diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3c9b0fda64ac..5dcabc98432f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4265,7 +4265,9 @@ DEFINE_STATIC_KEY_FALSE(sched_numa_balancing); #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); @@ -4273,13 +4275,22 @@ 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 *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; @@ -4289,8 +4300,10 @@ 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 083be6af29d7..a1be94ea80ba 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -115,6 +115,7 @@ static int sixty = 60; static int __maybe_unused neg_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; @@ -1808,7 +1809,7 @@ static struct ctl_table kern_table[] = { .mode = 0644, .proc_handler = sysctl_numa_balancing, .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_ONE, + .extra2 = &three, }, #endif /* CONFIG_NUMA_BALANCING */ { diff --git a/mm/migrate.c b/mm/migrate.c index b7c27abb0e5c..286c84c014dd 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -50,6 +50,7 @@ #include <linux/ptrace.h> #include <linux/oom.h> #include <linux/memory.h> +#include <linux/sched/sysctl.h> #include <asm/tlbflush.h> @@ -2103,16 +2104,30 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) { int page_lru; int nr_pages = thp_nr_pages(page); + int order = compound_order(page); - VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page); + VM_BUG_ON_PAGE(order && !PageTransHuge(page), page); /* Do not migrate THP mapped by multiple processes */ if (PageTransHuge(page) && total_mapcount(page) > 1) return 0; /* Avoid migrating to a node that is nearly full */ - if (!migrate_balanced_pgdat(pgdat, nr_pages)) + if (!migrate_balanced_pgdat(pgdat, nr_pages)) { + 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 fb9584641ac7..8ec955404bd1 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -56,6 +56,7 @@ #include <linux/swapops.h> #include <linux/balloon_compaction.h> +#include <linux/sched/sysctl.h> #include "internal.h" @@ -3908,6 +3909,12 @@ static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx) return false; } +/* + * 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 highest_zoneidx @@ -3929,6 +3936,15 @@ static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx) 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, highest_zoneidx)) return true; }
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" <ying.huang@intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Rik van Riel <riel@surriel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Wei Xu <weixugc@google.com> Cc: osalvador <osalvador@suse.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org --- Documentation/admin-guide/sysctl/kernel.rst | 29 ++++++++++++++------- include/linux/sched/sysctl.h | 10 +++++++ kernel/sched/core.c | 21 ++++++++++++--- kernel/sysctl.c | 3 ++- mm/migrate.c | 19 ++++++++++++-- mm/vmscan.c | 16 ++++++++++++ 6 files changed, 82 insertions(+), 16 deletions(-)