diff options
| -rw-r--r-- | Documentation/kernel-parameters.txt | 43 | ||||
| -rw-r--r-- | arch/i386/kernel/smpboot.c | 1 | ||||
| -rw-r--r-- | arch/ia64/kernel/setup.c | 6 | ||||
| -rw-r--r-- | arch/ppc/xmon/xmon.c | 2 | ||||
| -rw-r--r-- | include/asm-i386/topology.h | 1 | ||||
| -rw-r--r-- | include/asm-ia64/topology.h | 2 | ||||
| -rw-r--r-- | include/asm-mips/mach-ip27/topology.h | 1 | ||||
| -rw-r--r-- | include/asm-powerpc/topology.h | 1 | ||||
| -rw-r--r-- | include/asm-x86_64/topology.h | 1 | ||||
| -rw-r--r-- | include/linux/sched.h | 9 | ||||
| -rw-r--r-- | include/linux/topology.h | 2 | ||||
| -rw-r--r-- | kernel/sched.c | 468 |
12 files changed, 527 insertions, 10 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index dd0bfc291a68..fe11fccf7e41 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -856,6 +856,49 @@ running once the system is up. mga= [HW,DRM] + migration_cost= + [KNL,SMP] debug: override scheduler migration costs + Format: <level-1-usecs>,<level-2-usecs>,... + This debugging option can be used to override the + default scheduler migration cost matrix. The numbers + are indexed by 'CPU domain distance'. + E.g. migration_cost=1000,2000,3000 on an SMT NUMA + box will set up an intra-core migration cost of + 1 msec, an inter-core migration cost of 2 msecs, + and an inter-node migration cost of 3 msecs. + + WARNING: using the wrong values here can break + scheduler performance, so it's only for scheduler + development purposes, not production environments. + + migration_debug= + [KNL,SMP] migration cost auto-detect verbosity + Format=<0|1|2> + If a system's migration matrix reported at bootup + seems erroneous then this option can be used to + increase verbosity of the detection process. + We default to 0 (no extra messages), 1 will print + some more information, and 2 will be really + verbose (probably only useful if you also have a + serial console attached to the system). + + migration_factor= + [KNL,SMP] multiply/divide migration costs by a factor + Format=<percent> + This debug option can be used to proportionally + increase or decrease the auto-detected migration + costs for all entries of the migration matrix. + E.g. migration_factor=150 will increase migration + costs by 50%. (and thus the scheduler will be less + eager migrating cache-hot tasks) + migration_factor=80 will decrease migration costs + by 20%. (thus the scheduler will be more eager to + migrate tasks) + + WARNING: using the wrong values here can break + scheduler performance, so it's only for scheduler + development purposes, not production environments. + mousedev.tap_time= [MOUSE] Maximum time between finger touching and leaving touchpad surface for touch to be considered diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c index b3c2e2c26743..a9bf5f222e47 100644 --- a/arch/i386/kernel/smpboot.c +++ b/arch/i386/kernel/smpboot.c @@ -1096,6 +1096,7 @@ static void smp_tune_scheduling (void) cachesize = 16; /* Pentiums, 2x8kB cache */ bandwidth = 100; } + max_cache_size = cachesize * 1024; } } diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c index d91c8ff2c0d7..0daa8fa9ef32 100644 --- a/arch/ia64/kernel/setup.c +++ b/arch/ia64/kernel/setup.c @@ -696,6 +696,7 @@ static void get_max_cacheline_size (void) { unsigned long line_size, max = 1; + unsigned int cache_size = 0; u64 l, levels, unique_caches; pal_cache_config_info_t cci; s64 status; @@ -725,6 +726,8 @@ get_max_cacheline_size (void) line_size = 1 << cci.pcci_line_size; if (line_size > max) max = line_size; + if (cache_size < cci.pcci_cache_size) + cache_size = cci.pcci_cache_size; if (!cci.pcci_unified) { status = ia64_pal_cache_config_info(l, /* cache_type (instruction)= */ 1, @@ -741,6 +744,9 @@ get_max_cacheline_size (void) ia64_i_cache_stride_shift = cci.pcci_stride; } out: +#ifdef CONFIG_SMP + max_cache_size = max(max_cache_size, cache_size); +#endif if (max > ia64_max_cacheline_size) ia64_max_cacheline_size = max; } diff --git a/arch/ppc/xmon/xmon.c b/arch/ppc/xmon/xmon.c index 2b483b4f1602..9075a7538e26 100644 --- a/arch/ppc/xmon/xmon.c +++ b/arch/ppc/xmon/xmon.c @@ -99,7 +99,7 @@ static void remove_bpts(void); static void insert_bpts(void); static struct bpt *at_breakpoint(unsigned pc); static void bpt_cmds(void); -static void cacheflush(void); +void cacheflush(void); #ifdef CONFIG_SMP static void cpu_cmd(void); #endif /* CONFIG_SMP */ diff --git a/include/asm-i386/topology.h b/include/asm-i386/topology.h index 0ec27c9e8e45..d7e19eb344b7 100644 --- a/include/asm-i386/topology.h +++ b/include/asm-i386/topology.h @@ -72,7 +72,6 @@ static inline int node_to_first_cpu(int node) .max_interval = 32, \ .busy_factor = 32, \ .imbalance_pct = 125, \ - .cache_hot_time = (10*1000000), \ .cache_nice_tries = 1, \ .busy_idx = 3, \ .idle_idx = 1, \ diff --git a/include/asm-ia64/topology.h b/include/asm-ia64/topology.h index f7c330467e7e..d8aae4da3978 100644 --- a/include/asm-ia64/topology.h +++ b/include/asm-ia64/topology.h @@ -55,7 +55,6 @@ void build_cpu_to_node_map(void); .max_interval = 4, \ .busy_factor = 64, \ .imbalance_pct = 125, \ - .cache_hot_time = (10*1000000), \ .per_cpu_gain = 100, \ .cache_nice_tries = 2, \ .busy_idx = 2, \ @@ -81,7 +80,6 @@ void build_cpu_to_node_map(void); .max_interval = 8*(min(num_online_cpus(), 32)), \ .busy_factor = 64, \ .imbalance_pct = 125, \ - .cache_hot_time = (10*1000000), \ .cache_nice_tries = 2, \ .busy_idx = 3, \ .idle_idx = 2, \ diff --git a/include/asm-mips/mach-ip27/topology.h b/include/asm-mips/mach-ip27/topology.h index 82141c711c33..59d26b52ba32 100644 --- a/include/asm-mips/mach-ip27/topology.h +++ b/include/asm-mips/mach-ip27/topology.h @@ -27,7 +27,6 @@ extern unsigned char __node_distances[MAX_COMPACT_NODES][MAX_COMPACT_NODES]; .max_interval = 32, \ .busy_factor = 32, \ .imbalance_pct = 125, \ - .cache_hot_time = (10*1000), \ .cache_nice_tries = 1, \ .per_cpu_gain = 100, \ .flags = SD_LOAD_BALANCE \ diff --git a/include/asm-powerpc/topology.h b/include/asm-powerpc/topology.h index 9f3d4da261c4..1e19cd00af25 100644 --- a/include/asm-powerpc/topology.h +++ b/include/asm-powerpc/topology.h @@ -39,7 +39,6 @@ static inline int node_to_first_cpu(int node) .max_interval = 32, \ .busy_factor = 32, \ .imbalance_pct = 125, \ - .cache_hot_time = (10*1000000), \ .cache_nice_tries = 1, \ .per_cpu_gain = 100, \ .busy_idx = 3, \ diff --git a/include/asm-x86_64/topology.h b/include/asm-x86_64/topology.h index 7d82bc56b9fa..2fa7f27381b4 100644 --- a/include/asm-x86_64/topology.h +++ b/include/asm-x86_64/topology.h @@ -39,7 +39,6 @@ extern int __node_distance(int, int); .max_interval = 32, \ .busy_factor = 32, \ .imbalance_pct = 125, \ - .cache_hot_time = (10*1000000), \ .cache_nice_tries = 2, \ .busy_idx = 3, \ .idle_idx = 2, \ diff --git a/include/linux/sched.h b/include/linux/sched.h index 3b74c4bf2934..5d6b9228bba9 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -631,7 +631,14 @@ struct sched_domain { extern void partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2); -#endif /* CONFIG_SMP */ + +/* + * Maximum cache size the migration-costs auto-tuning code will + * search from: + */ +extern unsigned int max_cache_size; + +#endif /* CONFIG_SMP */ struct io_context; /* See blkdev.h */ diff --git a/include/linux/topology.h b/include/linux/topology.h index 3df1d474e5c5..315a5163d6a0 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -86,7 +86,6 @@ .max_interval = 2, \ .busy_factor = 8, \ .imbalance_pct = 110, \ - .cache_hot_time = 0, \ .cache_nice_tries = 0, \ .per_cpu_gain = 25, \ .busy_idx = 0, \ @@ -117,7 +116,6 @@ .max_interval = 4, \ .busy_factor = 64, \ .imbalance_pct = 125, \ - .cache_hot_time = (5*1000000/2), \ .cache_nice_tries = 1, \ .per_cpu_gain = 100, \ .busy_idx = 2, \ diff --git a/kernel/sched.c b/kernel/sched.c index c0c60c926d5e..98461de1ab65 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -34,6 +34,7 @@ #include <linux/notifier.h> #include <linux/profile.h> #include <linux/suspend.h> +#include <linux/vmalloc.h> #include <linux/blkdev.h> #include <linux/delay.h> #include <linux/smp.h> @@ -5082,7 +5083,470 @@ static void init_sched_build_groups(struct sched_group groups[], cpumask_t span, #define SD_NODES_PER_DOMAIN 16 +/* + * Self-tuning task migration cost measurement between source and target CPUs. + * + * This is done by measuring the cost of manipulating buffers of varying + * sizes. For a given buffer-size here are the steps that are taken: + * + * 1) the source CPU reads+dirties a shared buffer + * 2) the target CPU reads+dirties the same shared buffer + * + * We measure how long they take, in the following 4 scenarios: + * + * - source: CPU1, target: CPU2 | cost1 + * - source: CPU2, target: CPU1 | cost2 + * - source: CPU1, target: CPU1 | cost3 + * - source: CPU2, target: CPU2 | cost4 + * + * We then calculate the cost3+cost4-cost1-cost2 difference - this is + * the cost of migration. + * + * We then start off from a small buffer-size and iterate up to larger + * buffer sizes, in 5% steps - measuring each buffer-size separately, and + * doing a maximum search for the cost. (The maximum cost for a migration + * normally occurs when the working set size is around the effective cache + * size.) + */ +#define SEARCH_SCOPE 2 +#define MIN_CACHE_SIZE (64*1024U) +#define DEFAULT_CACHE_SIZE (5*1024*1024U) +#define ITERATIONS 2 +#define SIZE_THRESH 130 +#define COST_THRESH 130 + +/* + * The migration cost is a function of 'domain distance'. Domain + * distance is the number of steps a CPU has to iterate down its + * domain tree to share a domain with the other CPU. The farther + * two CPUs are from each other, the larger the distance gets. + * + * Note that we use the distance only to cache measurement results, + * the distance value is not used numerically otherwise. When two + * CPUs have the same distance it is assumed that the migration + * cost is the same. (this is a simplification but quite practical) + */ +#define MAX_DOMAIN_DISTANCE 32 + +static unsigned long long migration_cost[MAX_DOMAIN_DISTANCE] = + { [ 0 ... MAX_DOMAIN_DISTANCE-1 ] = -1LL }; + +/* + * Allow override of migration cost - in units of microseconds. + * E.g. migration_cost=1000,2000,3000 will set up a level-1 cost + * of 1 msec, level-2 cost of 2 msecs and level3 cost of 3 msecs: + */ +static int __init migration_cost_setup(char *str) +{ + int ints[MAX_DOMAIN_DISTANCE+1], i; + + str = get_options(str, ARRAY_SIZE(ints), ints); + + printk("#ints: %d\n", ints[0]); + for (i = 1; i <= ints[0]; i++) { + migration_cost[i-1] = (unsigned long long)ints[i]*1000; + printk("migration_cost[%d]: %Ld\n", i-1, migration_cost[i-1]); + } + return 1; +} + +__setup ("migration_cost=", migration_cost_setup); + +/* + * Global multiplier (divisor) for migration-cutoff values, + * in percentiles. E.g. use a value of 150 to get 1.5 times + * longer cache-hot cutoff times. + * + * (We scale it from 100 to 128 to long long handling easier.) + */ + +#define MIGRATION_FACTOR_SCALE 128 + +static unsigned int migration_factor = MIGRATION_FACTOR_SCALE; + +static int __init setup_migration_factor(char *str) +{ + get_option(&str, &migration_factor); + migration_factor = migration_factor * MIGRATION_FACTOR_SCALE / 100; + return 1; +} + +__setup("migration_factor=", setup_migration_factor); + +/* + * Estimated distance of two CPUs, measured via the number of domains + * we have to pass for the two CPUs to be in the same span: + */ +static unsigned long domain_distance(int cpu1, int cpu2) +{ + unsigned long distance = 0; + struct sched_domain *sd; + + for_each_domain(cpu1, sd) { + WARN_ON(!cpu_isset(cpu1, sd->span)); + if (cpu_isset(cpu2, sd->span)) + return distance; + distance++; + } + if (distance >= MAX_DOMAIN_DISTANCE) { + WARN_ON(1); + distance = MAX_DOMAIN_DISTANCE-1; + } + + return distance; +} + +static unsigned int migration_debug; + +static int __init setup_migration_debug(char *str) +{ + get_option(&str, &migration_debug); + return 1; +} + +__setup("migration_debug=", setup_migration_debug); + +/* + * Maximum cache-size that the scheduler should try to measure. + * Architectures with larger caches should tune this up during + * bootup. Gets used in the domain-setup code (i.e. during SMP + * bootup). + */ +unsigned int max_cache_size; + +static int __init setup_max_cache_size(char *str) +{ + get_option(&str, &max_cache_size); + return 1; +} + +__setup("max_cache_size=", setup_max_cache_size); + +/* + * Dirty a big buffer in a hard-to-predict (for the L2 cache) way. This + * is the operation that is timed, so we try to generate unpredictable + * cachemisses that still end up filling the L2 cache: + */ +static void touch_cache(void *__cache, unsigned long __size) +{ + unsigned long size = __size/sizeof(long), chunk1 = size/3, + chunk2 = 2*size/3; + unsigned long *cache = __cache; + int i; + + for (i = 0; i < size/6; i += 8) { + switch (i % 6) { + case 0: cache[i]++; + case 1: cache[size-1-i]++; + case 2: cache[chunk1-i]++; + case 3: cache[chunk1+i]++; + case 4: cache[chunk2-i]++; + case 5: cache[chunk2+i]++; + } + } +} + +/* + * Measure the cache-cost of one task migration. Returns in units of nsec. + */ +static unsigned long long measure_one(void *cache, unsigned long size, + int source, int target) +{ + cpumask_t mask, saved_mask; + unsigned long long t0, t1, t2, t3, cost; + + saved_mask = current->cpus_allowed; + + /* + * Flush source caches to RAM and invalidate them: + */ + sched_cacheflush(); + + /* + * Migrate to the source CPU: + */ + mask = cpumask_of_cpu(source); + set_cpus_allowed(current, mask); + WARN_ON(smp_processor_id() != source); + + /* + * Dirty the working set: + */ + t0 = sched_clock(); + touch_cache(cache, size); + t1 = sched_clock(); + + /* + * Migrate to the target CPU, dirty the L2 cache and access + * the shared buffer. (which represents the working set + * of a migrated task.) + */ + mask = cpumask_of_cpu(target); + set_cpus_allowed(current, mask); + WARN_ON(smp_processor_id() != target); + + t2 = sched_clock(); + touch_cache(cache, size); + t3 = sched_clock(); + + cost = t1-t0 + t3-t2; + + if (migration_debug >= 2) + printk("[%d->%d]: %8Ld %8Ld %8Ld => %10Ld.\n", + source, target, t1-t0, t1-t0, t3-t2, cost); + /* + * Flush target caches to RAM and invalidate them: + */ + sched_cacheflush(); + + set_cpus_allowed(current, saved_mask); + + return cost; +} + +/* + * Measure a series of task migrations and return the average + * result. Since this code runs early during bootup the system + * is 'undisturbed' and the average latency makes sense. + * + * The algorithm in essence auto-detects the relevant cache-size, + * so it will properly detect different cachesizes for different + * cache-hierarchies, depending on how the CPUs are connected. + * + * Architectures can prime the upper limit of the search range via + * max_cache_size, otherwise the search range defaults to 20MB...64K. + */ +static unsigned long long +measure_cost(int cpu1, int cpu2, void *cache, unsigned int size) +{ + unsigned long long cost1, cost2; + int i; + + /* + * Measure the migration cost of 'size' bytes, over an + * average of 10 runs: + * + * (We perturb the cache size by a small (0..4k) + * value to compensate size/alignment related artifacts. + * We also subtract the cost of the operation done on + * the same CPU.) + */ + cost1 = 0; + + /* + * dry run, to make sure we start off cache-cold on cpu1, + * and to get any vmalloc pagefaults in advance: + */ + measure_one(cache, size, cpu1, cpu2); + for (i = 0; i < ITERATIONS; i++) + cost1 += measure_one(cache, size - i*1024, cpu1, cpu2); + + measure_one(cache, size, cpu2, cpu1); + for (i = 0; i < ITERATIONS; i++) + cost1 += measure_one(cache, size - i*1024, cpu2, cpu1); + + /* + * (We measure the non-migrating [cached] cost on both + * cpu1 and cpu2, to handle CPUs with different speeds) + */ + cost2 = 0; + + measure_one(cache, size, cpu1, cpu1); + for (i = 0; i < ITERATIONS; i++) + cost2 += measure_one(cache, size - i*1024, cpu1, cpu1); + + measure_one(cache, size, cpu2, cpu2); + for (i = 0; i < ITERATIONS; i++) + cost2 += measure_one(cache, size - i*1024, cpu2, cpu2); + + /* + * Get the per-iteration migration cost: + */ + do_div(cost1, 2*ITERATIONS); + do_div(cost2, 2*ITERATIONS); + + return cost1 - cost2; +} + +static unsigned long long measure_migration_cost(int cpu1, int cpu2) +{ + unsigned long long max_cost = 0, fluct = 0, avg_fluct = 0; + unsigned int max_size, size, size_found = 0; + long long cost = 0, prev_cost; + void *cache; + + /* + * Search from max_cache_size*5 down to 64K - the real relevant + * cachesize has to lie somewhere inbetween. + */ + if (max_cache_size) { + max_size = max(max_cache_size * SEARCH_SCOPE, MIN_CACHE_SIZE); + size = max(max_cache_size / SEARCH_SCOPE, MIN_CACHE_SIZE); + } else { + /* + * Since we have no estimation about the relevant + * search range + */ + max_size = DEFAULT_CACHE_SIZE * SEARCH_SCOPE; + size = MIN_CACHE_SIZE; + } + + if (!cpu_online(cpu1) || !cpu_online(cpu2)) { + printk("cpu %d and %d not both online!\n", cpu1, cpu2); + return 0; + } + + /* + * Allocate the working set: + */ + cache = vmalloc(max_size); + if (!cache) { + printk("could not vmalloc %d bytes for cache!\n", 2*max_size); + return 1000000; // return 1 msec on very small boxen + } + + while (size <= max_size) { + prev_cost = cost; + cost = measure_cost(cpu1, cpu2, cache, size); + + /* + * Update the max: + */ + if (cost > 0) { + if (max_cost < cost) { + max_cost = cost; + size_found = size; + } + } + /* + * Calculate average fluctuation, we use this to prevent + * noise from triggering an early break out of the loop: + */ + fluct = abs(cost - prev_cost); + avg_fluct = (avg_fluct + fluct)/2; + + if (migration_debug) + printk("-> [%d][%d][%7d] %3ld.%ld [%3ld.%ld] (%ld): (%8Ld %8Ld)\n", + cpu1, cpu2, size, + (long)cost / 1000000, + ((long)cost / 100000) % 10, + (long)max_cost / 1000000, + ((long)max_cost / 100000) % 10, + domain_distance(cpu1, cpu2), + cost, avg_fluct); + + /* + * If we iterated at least 20% past the previous maximum, + * and the cost has dropped by more than 20% already, + * (taking fluctuations into account) then we assume to + * have found the maximum and break out of the loop early: + */ + if (size_found && (size*100 > size_found*SIZE_THRESH)) + if (cost+avg_fluct <= 0 || + max_cost*100 > (cost+avg_fluct)*COST_THRESH) { + + if (migration_debug) + printk("-> found max.\n"); + break; + } + /* + * Increase the cachesize in 5% steps: + */ + size = size * 20 / 19; + } + + if (migration_debug) + printk("[%d][%d] working set size found: %d, cost: %Ld\n", + cpu1, cpu2, size_found, max_cost); + + vfree(cache); + + /* + * A task is considered 'cache cold' if at least 2 times + * the worst-case cost of migration has passed. + * + * (this limit is only listened to if the load-balancing + * situation is 'nice' - if there is a large imbalance we + * ignore it for the sake of CPU utilization and + * processing fairness.) + */ + return 2 * max_cost * migration_factor / MIGRATION_FACTOR_SCALE; +} + +static void calibrate_migration_costs(const cpumask_t *cpu_map) +{ + int cpu1 = -1, cpu2 = -1, cpu, orig_cpu = raw_smp_processor_id(); + unsigned long j0, j1, distance, max_distance = 0; + struct sched_domain *sd; + + j0 = jiffies; + + /* + * First pass - calculate the cacheflush times: + */ + for_each_cpu_mask(cpu1, *cpu_map) { + for_each_cpu_mask(cpu2, *cpu_map) { + if (cpu1 == cpu2) + continue; + distance = domain_distance(cpu1, cpu2); + max_distance = max(max_distance, distance); + /* + * No result cached yet? + */ + if (migration_cost[distance] == -1LL) + migration_cost[distance] = + measure_migration_cost(cpu1, cpu2); + } + } + /* + * Second pass - update the sched domain hierarchy with + * the new cache-hot-time estimations: + */ + for_each_cpu_mask(cpu, *cpu_map) { + distance = 0; + for_each_domain(cpu, sd) { + sd->cache_hot_time = migration_cost[distance]; + distance++; + } + } + /* + * Print the matrix: + */ + if (migration_debug) + printk("migration: max_cache_size: %d, cpu: %d MHz:\n", + max_cache_size, +#ifdef CONFIG_X86 + cpu_khz/1000 +#else + -1 +#endif + ); + printk("migration_cost="); + for (distance = 0; distance <= max_distance; distance++) { + if (distance) + printk(","); + printk("%ld", (long)migration_cost[distance] / 1000); + } + printk("\n"); + j1 = jiffies; + if (migration_debug) + printk("migration: %ld seconds\n", (j1-j0)/HZ); + + /* + * Move back to the original CPU. NUMA-Q gets confused + * if we migrate to another quad during bootup. + */ + if (raw_smp_processor_id() != orig_cpu) { + cpumask_t mask = cpumask_of_cpu(orig_cpu), + saved_mask = current->cpus_allowed; + + set_cpus_allowed(current, mask); + set_cpus_allowed(current, saved_mask); + } +} + #ifdef CONFIG_NUMA + /** * find_next_best_node - find the next node to include in a sched_domain * @node: node whose sched_domain we're building @@ -5448,6 +5912,10 @@ next_sg: #endif cpu_attach_domain(sd, i); } + /* + * Tune cache-hot values: + */ + calibrate_migration_costs(cpu_map); } /* * Set up scheduler domains and groups. Callers must hold the hotplug lock. |