/*
- * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2000-2007 Apple Computer, Inc. All rights reserved.
*
- * @APPLE_LICENSE_OSREFERENCE_HEADER_START@
- *
- * This file contains Original Code and/or Modifications of Original Code
- * as defined in and that are subject to the Apple Public Source License
- * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. The rights granted to you under the
- * License may not be used to create, or enable the creation or
- * redistribution of, unlawful or unlicensed copies of an Apple operating
- * system, or to circumvent, violate, or enable the circumvention or
- * violation of, any terms of an Apple operating system software license
- * agreement.
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
- * Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
*
- * The Original Code and all software distributed under the License are
- * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
- * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
- * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
- * Please see the License for the specific language governing rights and
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
* limitations under the License.
*
- * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
*/
/*
* @OSF_COPYRIGHT@
*/
-/*
+/*
* Mach Operating System
* Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
* All Rights Reserved.
- *
+ *
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
- *
+ *
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
- *
+ *
* Carnegie Mellon requests users of this software to return to
- *
+ *
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
- *
+ *
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
#include <kern/assert.h>
#include <kern/processor.h>
#include <kern/thread.h>
-
-uint32_t avenrun[3] = {0, 0, 0};
-uint32_t mach_factor[3] = {0, 0, 0};
+#if CONFIG_TELEMETRY
+#include <kern/telemetry.h>
+#endif
+
+#include <sys/kdebug.h>
+
+uint32_t avenrun[3] = {0, 0, 0};
+uint32_t mach_factor[3] = {0, 0, 0};
+uint32_t sched_load_average, sched_mach_factor;
+
+#if defined(CONFIG_SCHED_TIMESHARE_CORE)
/*
* Values are scaled by LOAD_SCALE, defined in processor_info.h
*/
-#define base(n) ((n) << SCHED_TICK_SHIFT)
-#define frac(n) (((base(n) - 1) * LOAD_SCALE) / base(n))
+#define base(n) ((n) << SCHED_TICK_SHIFT)
+#define frac(n) (((base(n) - 1) * LOAD_SCALE) / base(n))
-static uint32_t fract[3] = {
- frac(5), /* 5 second average */
- frac(30), /* 30 second average */
- frac(60), /* 1 minute average */
+static uint32_t fract[3] = {
+ frac(5), /* 5 second average */
+ frac(30), /* 30 second average */
+ frac(60), /* 1 minute average */
};
#undef base
#undef frac
-static unsigned int sched_nrun;
+#endif /* CONFIG_SCHED_TIMESHARE_CORE */
-typedef void (*sched_avg_comp_t)(
- void *param);
+static unsigned int sched_nrun;
-#define SCHED_AVG_SECS(n) ((n) << SCHED_TICK_SHIFT)
+typedef void (*sched_avg_comp_t)(
+ void *param);
static struct sched_average {
- sched_avg_comp_t comp;
- void *param;
- int period;
- int tick;
+ sched_avg_comp_t comp;
+ void *param;
+ int period; /* in seconds */
+ uint64_t deadline;
} sched_average[] = {
- { compute_averunnable, &sched_nrun, SCHED_AVG_SECS(5), 0 },
- { compute_stack_target, NULL, SCHED_AVG_SECS(5), 1 },
+ { compute_averunnable, &sched_nrun, 5, 0 },
+ { compute_stack_target, NULL, 5, 1 },
+ { compute_pageout_gc_throttle, NULL, 1, 0 },
+ { compute_pmap_gc_throttle, NULL, 60, 0 },
+#if CONFIG_TELEMETRY
+ { compute_telemetry, NULL, 1, 0 },
+#endif
{ NULL, NULL, 0, 0 }
};
-typedef struct sched_average *sched_average_t;
+typedef struct sched_average *sched_average_t;
+
+/*
+ * Scheduler load calculation algorithm
+ *
+ * The scheduler load values provide an estimate of the number of runnable
+ * timeshare threads in the system at various priority bands. The load
+ * ultimately affects the priority shifts applied to all threads in a band
+ * causing them to timeshare with other threads in the system. The load is
+ * maintained in buckets, with each bucket corresponding to a priority band.
+ *
+ * Each runnable thread on the system contributes its load to its priority
+ * band and to the bands above it. The contribution of a thread to the bands
+ * above it is not strictly 1:1 and is weighted based on the priority band
+ * of the thread. The rules of thread load contribution to each of its higher
+ * bands are as follows:
+ *
+ * - DF threads: Upto (2 * NCPUs) threads
+ * - UT threads: Upto NCPUs threads
+ * - BG threads: Upto 1 thread
+ *
+ * To calculate the load values, the various run buckets are sampled (every
+ * sched_load_compute_interval_abs) and the weighted contributions of the the
+ * lower bucket threads are added. The resultant value is plugged into an
+ * exponentially weighted moving average formula:
+ * new-load = alpha * old-load + (1 - alpha) * run-bucket-sample-count
+ * (where, alpha < 1)
+ * The calculations for the scheduler load are done using fixpoint math with
+ * a scale factor of 16 to avoid expensive divides and floating point
+ * operations. The final load values are a smooth curve representative of
+ * the actual number of runnable threads in a priority band.
+ */
+
+/* Maintains the current (scaled for fixpoint) load in various buckets */
+uint32_t sched_load[TH_BUCKET_MAX];
+/*
+ * Alpha factor for the EWMA alogrithm. The current values are chosen as
+ * 6:10 ("old load":"new samples") to make sure the scheduler reacts fast
+ * enough to changing system load but does not see too many spikes from bursty
+ * activity. The current values ensure that the scheduler would converge
+ * to the latest load in 2-3 sched_load_compute_interval_abs intervals
+ * (which amounts to ~30-45ms with current values).
+ */
+#define SCHED_LOAD_EWMA_ALPHA_OLD 6
+#define SCHED_LOAD_EWMA_ALPHA_NEW 10
+#define SCHED_LOAD_EWMA_ALPHA_SHIFT 4
+static_assert((SCHED_LOAD_EWMA_ALPHA_OLD + SCHED_LOAD_EWMA_ALPHA_NEW) == (1ul << SCHED_LOAD_EWMA_ALPHA_SHIFT));
+
+/* For fixpoint EWMA, roundup the load to make it converge */
+#define SCHED_LOAD_EWMA_ROUNDUP(load) (((load) & (1ul << (SCHED_LOAD_EWMA_ALPHA_SHIFT - 1))) != 0)
+
+/* Macro to convert scaled sched load to a real load value */
+#define SCHED_LOAD_EWMA_UNSCALE(load) (((load) >> SCHED_LOAD_EWMA_ALPHA_SHIFT) + SCHED_LOAD_EWMA_ROUNDUP(load))
+
+/*
+ * Routine to capture the latest runnable counts and update sched_load */
void
-compute_averages(void)
+compute_sched_load(void)
{
- register processor_set_t pset = &default_pset;
- register int ncpus;
- register int nthreads, nshared;
- sched_average_t avg;
- register uint32_t factor_now = 0;
- register uint32_t average_now = 0;
- register uint32_t load_now = 0;
-
- if ((ncpus = pset->processor_count) > 0) {
- /*
- * Retrieve counts, ignoring
- * the current thread.
- */
- nthreads = pset->run_count - 1;
- nshared = pset->share_count;
-
- /*
- * Load average and mach factor calculations for
- * those which ask about these things.
- */
- average_now = nthreads * LOAD_SCALE;
-
- if (nthreads > ncpus)
- factor_now = (ncpus * LOAD_SCALE) / (nthreads + 1);
- else
- factor_now = (ncpus - nthreads) * LOAD_SCALE;
-
- pset->mach_factor = ((pset->mach_factor << 2) + factor_now) / 5;
- pset->load_average = ((pset->load_average << 2) + average_now) / 5;
-
- /*
- * Compute the timeshare priority
- * conversion factor based on loading.
- */
- if (nshared > nthreads)
- nshared = nthreads;
-
- if (nshared > ncpus) {
- if (ncpus > 1)
- load_now = nshared / ncpus;
- else
- load_now = nshared;
-
- if (load_now > NRQS - 1)
- load_now = NRQS - 1;
+ /*
+ * Retrieve a snapshot of the current run counts.
+ *
+ * Why not a bcopy()? Because we need atomic word-sized reads of sched_run_buckets,
+ * not byte-by-byte copy.
+ */
+ uint32_t ncpus = processor_avail_count;
+ uint32_t load_now[TH_BUCKET_MAX];
+
+ load_now[TH_BUCKET_RUN] = sched_run_buckets[TH_BUCKET_RUN];
+ load_now[TH_BUCKET_FIXPRI] = sched_run_buckets[TH_BUCKET_FIXPRI];
+ load_now[TH_BUCKET_SHARE_FG] = sched_run_buckets[TH_BUCKET_SHARE_FG];
+ load_now[TH_BUCKET_SHARE_DF] = sched_run_buckets[TH_BUCKET_SHARE_DF];
+ load_now[TH_BUCKET_SHARE_UT] = sched_run_buckets[TH_BUCKET_SHARE_UT];
+ load_now[TH_BUCKET_SHARE_BG] = sched_run_buckets[TH_BUCKET_SHARE_BG];
+
+ assert(load_now[TH_BUCKET_RUN] >= 0);
+ assert(load_now[TH_BUCKET_FIXPRI] >= 0);
+
+ uint32_t nthreads = load_now[TH_BUCKET_RUN];
+ uint32_t nfixpri = load_now[TH_BUCKET_FIXPRI];
+
+ KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
+ MACHDBG_CODE(DBG_MACH_SCHED, MACH_SCHED_LOAD) | DBG_FUNC_NONE,
+ load_now[TH_BUCKET_FIXPRI], (load_now[TH_BUCKET_SHARE_FG] + load_now[TH_BUCKET_SHARE_DF]),
+ load_now[TH_BUCKET_SHARE_BG], load_now[TH_BUCKET_SHARE_UT], 0);
+
+ /*
+ * Compute the timeshare priority conversion factor based on loading.
+ * Because our counters may be incremented and accessed
+ * concurrently with respect to each other, we may have
+ * windows where the invariant (nthreads - nfixpri) == (fg + df + bg + ut)
+ * is broken, so truncate values in these cases.
+ */
+ uint32_t timeshare_threads = (nthreads - nfixpri);
+ for (uint32_t i = TH_BUCKET_SHARE_FG; i <= TH_BUCKET_SHARE_BG; i++) {
+ if (load_now[i] > timeshare_threads) {
+ load_now[i] = timeshare_threads;
}
+ }
- /*
- * The conversion factor consists of
- * two components: a fixed value based
- * on the absolute time unit, and a
- * dynamic portion based on loading.
- *
- * Zero loading results in a out of range
- * shift count. Accumulated usage is ignored
- * during conversion and new usage deltas
- * are discarded.
- */
- pset->pri_shift = sched_pri_shift - sched_load_shifts[load_now];
+ /*
+ * Default threads contribute up to (NCPUS * 2) of load to FG threads
+ */
+ if (load_now[TH_BUCKET_SHARE_DF] <= (ncpus * 2)) {
+ load_now[TH_BUCKET_SHARE_FG] += load_now[TH_BUCKET_SHARE_DF];
+ } else {
+ load_now[TH_BUCKET_SHARE_FG] += (ncpus * 2);
}
- else {
- pset->mach_factor = pset->load_average = 0;
- pset->pri_shift = INT8_MAX;
- nthreads = pset->run_count;
+
+ /*
+ * Utility threads contribute up to NCPUS of load to FG & DF threads
+ */
+ if (load_now[TH_BUCKET_SHARE_UT] <= ncpus) {
+ load_now[TH_BUCKET_SHARE_FG] += load_now[TH_BUCKET_SHARE_UT];
+ load_now[TH_BUCKET_SHARE_DF] += load_now[TH_BUCKET_SHARE_UT];
+ } else {
+ load_now[TH_BUCKET_SHARE_FG] += ncpus;
+ load_now[TH_BUCKET_SHARE_DF] += ncpus;
}
/*
- * Sample total running threads.
+ * BG threads contribute up to 1 thread worth of load to FG, DF and UT threads
+ */
+ if (load_now[TH_BUCKET_SHARE_BG] > 0) {
+ load_now[TH_BUCKET_SHARE_FG] += 1;
+ load_now[TH_BUCKET_SHARE_DF] += 1;
+ load_now[TH_BUCKET_SHARE_UT] += 1;
+ }
+
+ /*
+ * The conversion factor consists of two components:
+ * a fixed value based on the absolute time unit (sched_fixed_shift),
+ * and a dynamic portion based on load (sched_load_shifts).
+ *
+ * Zero load results in a out of range shift count.
+ */
+
+ for (uint32_t i = TH_BUCKET_SHARE_FG; i <= TH_BUCKET_SHARE_BG; i++) {
+ uint32_t bucket_load = 0;
+
+ if (load_now[i] > ncpus) {
+ /* Normalize the load to number of CPUs */
+ if (ncpus > 1) {
+ bucket_load = load_now[i] / ncpus;
+ } else {
+ bucket_load = load_now[i];
+ }
+
+ if (bucket_load > MAX_LOAD) {
+ bucket_load = MAX_LOAD;
+ }
+ }
+ /* Plug the load values into the EWMA algorithm to calculate (scaled for fixpoint) sched_load */
+ sched_load[i] = (sched_load[i] * SCHED_LOAD_EWMA_ALPHA_OLD) + ((bucket_load << SCHED_LOAD_EWMA_ALPHA_SHIFT) * SCHED_LOAD_EWMA_ALPHA_NEW);
+ sched_load[i] = sched_load[i] >> SCHED_LOAD_EWMA_ALPHA_SHIFT;
+ }
+
+ KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
+ MACHDBG_CODE(DBG_MACH_SCHED, MACH_SCHED_LOAD_EFFECTIVE) | DBG_FUNC_NONE,
+ SCHED_LOAD_EWMA_UNSCALE(sched_load[TH_BUCKET_SHARE_FG]), SCHED_LOAD_EWMA_UNSCALE(sched_load[TH_BUCKET_SHARE_DF]),
+ SCHED_LOAD_EWMA_UNSCALE(sched_load[TH_BUCKET_SHARE_UT]), SCHED_LOAD_EWMA_UNSCALE(sched_load[TH_BUCKET_SHARE_BG]), 0);
+}
+
+void
+compute_averages(uint64_t stdelta)
+{
+ uint32_t nthreads = sched_run_buckets[TH_BUCKET_RUN] - 1;
+ uint32_t ncpus = processor_avail_count;
+
+ /* Update the global pri_shifts based on the latest values */
+ for (uint32_t i = TH_BUCKET_SHARE_FG; i <= TH_BUCKET_SHARE_BG; i++) {
+ uint32_t bucket_load = SCHED_LOAD_EWMA_UNSCALE(sched_load[i]);
+ sched_pri_shifts[i] = sched_fixed_shift - sched_load_shifts[bucket_load];
+ }
+
+ /*
+ * Sample total running threads for the load average calculation.
*/
sched_nrun = nthreads;
/*
- * Compute old-style Mach load averages.
+ * Load average and mach factor calculations for
+ * those which ask about these things.
*/
- {
- register int i;
+ uint32_t average_now = nthreads * LOAD_SCALE;
+ uint32_t factor_now;
- for (i = 0; i < 3; i++) {
+ if (nthreads > ncpus) {
+ factor_now = (ncpus * LOAD_SCALE) / (nthreads + 1);
+ } else {
+ factor_now = (ncpus - nthreads) * LOAD_SCALE;
+ }
+
+ /*
+ * For those statistics that formerly relied on being recomputed
+ * on timer ticks, advance by the approximate number of corresponding
+ * elapsed intervals, thus compensating for potential idle intervals.
+ */
+ for (uint32_t index = 0; index < stdelta; index++) {
+ sched_mach_factor = ((sched_mach_factor << 2) + factor_now) / 5;
+ sched_load_average = ((sched_load_average << 2) + average_now) / 5;
+ }
+
+ /*
+ * Compute old-style Mach load averages.
+ */
+ for (uint32_t index = 0; index < stdelta; index++) {
+ for (uint32_t i = 0; i < 3; i++) {
mach_factor[i] = ((mach_factor[i] * fract[i]) +
- (factor_now * (LOAD_SCALE - fract[i]))) / LOAD_SCALE;
+ (factor_now * (LOAD_SCALE - fract[i]))) / LOAD_SCALE;
avenrun[i] = ((avenrun[i] * fract[i]) +
- (average_now * (LOAD_SCALE - fract[i]))) / LOAD_SCALE;
+ (average_now * (LOAD_SCALE - fract[i]))) / LOAD_SCALE;
}
}
/*
- * Compute averages in other components.
+ * Compute averages in other components.
*/
- for (avg = sched_average; avg->comp != NULL; ++avg) {
- if (++avg->tick >= avg->period) {
- (*avg->comp)(avg->param);
- avg->tick = 0;
+ uint64_t abstime = mach_absolute_time();
+
+ for (sched_average_t avg = sched_average; avg->comp != NULL; ++avg) {
+ if (abstime >= avg->deadline) {
+ uint64_t period_abs = (avg->period * sched_one_second_interval);
+ uint64_t ninvokes = 1;
+
+ ninvokes += (abstime - avg->deadline) / period_abs;
+ ninvokes = MIN(ninvokes, SCHED_TICK_MAX_DELTA);
+
+ for (uint32_t index = 0; index < ninvokes; index++) {
+ (*avg->comp)(avg->param);
+ }
+ avg->deadline = abstime + period_abs;
}
}
}
projects / apple / xnu.git / blobdiff