#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 1
-#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 ] =
-/*
- * Architectures may override the migration cost and thus avoid
- * boot-time calibration. Unit is nanoseconds. Mostly useful for
- * virtualized hardware:
- */
-#ifdef CONFIG_DEFAULT_MIGRATION_COST
- CONFIG_DEFAULT_MIGRATION_COST
-#else
- -1LL
-#endif
-};
-
-/*
- * 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);
- unsigned long chunk1 = size / 3;
- unsigned long 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 10% steps:
- */
- size = size * 10 / 9;
- }
-
- 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
- );
- if (system_state == SYSTEM_BOOTING && num_online_cpus() > 1) {
- 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
/**
#endif
cpu_attach_domain(sd, i);
}
- /*
- * Tune cache-hot values:
- */
- calibrate_migration_costs(cpu_map);
return 0;
projects / linux-2.6 / commitdiff