// SPDX-License-Identifier: GPL-2.0
/*
 * DAMON-based LRU-lists Sorting
 *
 * Author: SeongJae Park <sj@kernel.org>
 */

#define pr_fmt(fmt) "damon-lru-sort: " fmt

#include <linux/damon.h>
#include <linux/kstrtox.h>
#include <linux/module.h>

#include "modules-common.h"

#ifdef MODULE_PARAM_PREFIX
#undef MODULE_PARAM_PREFIX
#endif
#define MODULE_PARAM_PREFIX "damon_lru_sort."

/*
 * Enable or disable DAMON_LRU_SORT.
 *
 * You can enable DAMON_LRU_SORT by setting the value of this parameter as
 * ``Y``.  Setting it as ``N`` disables DAMON_LRU_SORT.  Note that
 * DAMON_LRU_SORT could do no real monitoring and LRU-lists sorting due to the
 * watermarks-based activation condition.  Refer to below descriptions for the
 * watermarks parameter for this.
 */
static bool enabled __read_mostly;

/*
 * Make DAMON_LRU_SORT reads the input parameters again, except ``enabled``.
 *
 * Input parameters that updated while DAMON_LRU_SORT is running are not
 * applied by default.  Once this parameter is set as ``Y``, DAMON_LRU_SORT
 * reads values of parameters except ``enabled`` again.  Once the re-reading is
 * done, this parameter is set as ``N``.  If invalid parameters are found while
 * the re-reading, DAMON_LRU_SORT will be disabled.
 */
static bool commit_inputs __read_mostly;
module_param(commit_inputs, bool, 0600);

/*
 * Desired active to [in]active memory ratio in bp (1/10,000).
 *
 * While keeping the caps that set by other quotas, DAMON_LRU_SORT
 * automatically increases and decreases the effective level of the quota
 * aiming the LRU [de]prioritizations of the hot and cold memory resulting in
 * this active to [in]active memory ratio.  Value zero means disabling this
 * auto-tuning feature.
 *
 * Disabled by default.
 */
static unsigned long active_mem_bp __read_mostly;
module_param(active_mem_bp, ulong, 0600);

/*
 * Auto-tune monitoring intervals.
 *
 * If this parameter is set as ``Y``, DAMON_LRU_SORT automatically tunes
 * DAMON's sampling and aggregation intervals.  The auto-tuning aims to capture
 * meaningful amount of access events in each DAMON-snapshot, while keeping the
 * sampling interval 5 milliseconds in minimum, and 10 seconds in maximum.
 * Setting this as ``N`` disables the auto-tuning.
 *
 * Disabled by default.
 */
static bool autotune_monitoring_intervals __read_mostly;
module_param(autotune_monitoring_intervals, bool, 0600);

/*
 * Filter [non-]young pages accordingly for LRU [de]prioritizations.
 *
 * If this is set, check page level access (youngness) once again before each
 * LRU [de]prioritization operation.  LRU prioritization operation is skipped
 * if the page has not accessed since the last check (not young).  LRU
 * deprioritization operation is skipped if the page has accessed since the
 * last check (young).  The feature is enabled or disabled if this parameter is
 * set as ``Y`` or ``N``, respectively.
 *
 * Disabled by default.
 */
static bool filter_young_pages __read_mostly;
module_param(filter_young_pages, bool, 0600);

/*
 * Access frequency threshold for hot memory regions identification in permil.
 *
 * If a memory region is accessed in frequency of this or higher,
 * DAMON_LRU_SORT identifies the region as hot, and mark it as accessed on the
 * LRU list, so that it could not be reclaimed under memory pressure.  50% by
 * default.
 */
static unsigned long hot_thres_access_freq = 500;
module_param(hot_thres_access_freq, ulong, 0600);

/*
 * Time threshold for cold memory regions identification in microseconds.
 *
 * If a memory region is not accessed for this or longer time, DAMON_LRU_SORT
 * identifies the region as cold, and mark it as unaccessed on the LRU list, so
 * that it could be reclaimed first under memory pressure.  120 seconds by
 * default.
 */
static unsigned long cold_min_age __read_mostly = 120000000;
module_param(cold_min_age, ulong, 0600);

static struct damos_quota damon_lru_sort_quota = {
        /* Use up to 10 ms per 1 sec, by default */
        .ms = 10,
        .sz = 0,
        .reset_interval = 1000,
        /* Within the quota, mark hotter regions accessed first. */
        .weight_sz = 0,
        .weight_nr_accesses = 1,
        .weight_age = 1,
};
DEFINE_DAMON_MODULES_DAMOS_TIME_QUOTA(damon_lru_sort_quota);

static struct damos_watermarks damon_lru_sort_wmarks = {
        .metric = DAMOS_WMARK_FREE_MEM_RATE,
        .interval = 5000000,    /* 5 seconds */
        .high = 200,            /* 20 percent */
        .mid = 150,             /* 15 percent */
        .low = 50,              /* 5 percent */
};
DEFINE_DAMON_MODULES_WMARKS_PARAMS(damon_lru_sort_wmarks);

static struct damon_attrs damon_lru_sort_mon_attrs = {
        .sample_interval = 5000,        /* 5 ms */
        .aggr_interval = 100000,        /* 100 ms */
        .ops_update_interval = 0,
        .min_nr_regions = 10,
        .max_nr_regions = 1000,
};
DEFINE_DAMON_MODULES_MON_ATTRS_PARAMS(damon_lru_sort_mon_attrs);

/*
 * Start of the target memory region in physical address.
 *
 * The start physical address of memory region that DAMON_LRU_SORT will do work
 * against.  By default, biggest System RAM is used as the region.
 */
static unsigned long monitor_region_start __read_mostly;
module_param(monitor_region_start, ulong, 0600);

/*
 * End of the target memory region in physical address.
 *
 * The end physical address of memory region that DAMON_LRU_SORT will do work
 * against.  By default, biggest System RAM is used as the region.
 */
static unsigned long monitor_region_end __read_mostly;
module_param(monitor_region_end, ulong, 0600);

/*
 * Scale factor for DAMON_LRU_SORT to ops address conversion.
 *
 * This parameter must not be set to 0.
 */
static unsigned long addr_unit __read_mostly = 1;

/*
 * PID of the DAMON thread
 *
 * If DAMON_LRU_SORT is enabled, this becomes the PID of the worker thread.
 * Else, -1.
 */
static int kdamond_pid __read_mostly = -1;
module_param(kdamond_pid, int, 0400);

static struct damos_stat damon_lru_sort_hot_stat;
DEFINE_DAMON_MODULES_DAMOS_STATS_PARAMS(damon_lru_sort_hot_stat,
                lru_sort_tried_hot_regions, lru_sorted_hot_regions,
                hot_quota_exceeds);

static struct damos_stat damon_lru_sort_cold_stat;
DEFINE_DAMON_MODULES_DAMOS_STATS_PARAMS(damon_lru_sort_cold_stat,
                lru_sort_tried_cold_regions, lru_sorted_cold_regions,
                cold_quota_exceeds);

static struct damos_access_pattern damon_lru_sort_stub_pattern = {
        /* Find regions having PAGE_SIZE or larger size */
        .min_sz_region = PAGE_SIZE,
        .max_sz_region = ULONG_MAX,
        /* no matter its access frequency */
        .min_nr_accesses = 0,
        .max_nr_accesses = UINT_MAX,
        /* no matter its age */
        .min_age_region = 0,
        .max_age_region = UINT_MAX,
};

static struct damon_ctx *ctx;
static struct damon_target *target;

static struct damos *damon_lru_sort_new_scheme(
                struct damos_access_pattern *pattern, enum damos_action action)
{
        struct damos_quota quota = damon_lru_sort_quota;

        /* Use half of total quota for hot/cold pages sorting */
        quota.ms = quota.ms / 2;

        return damon_new_scheme(
                        /* find the pattern, and */
                        pattern,
                        /* (de)prioritize on LRU-lists */
                        action,
                        /* for each aggregation interval */
                        0,
                        /* under the quota. */
                        &quota,
                        /* (De)activate this according to the watermarks. */
                        &damon_lru_sort_wmarks,
                        NUMA_NO_NODE);
}

/* Create a DAMON-based operation scheme for hot memory regions */
static struct damos *damon_lru_sort_new_hot_scheme(unsigned int hot_thres)
{
        struct damos_access_pattern pattern = damon_lru_sort_stub_pattern;

        pattern.min_nr_accesses = hot_thres;
        return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_PRIO);
}

/* Create a DAMON-based operation scheme for cold memory regions */
static struct damos *damon_lru_sort_new_cold_scheme(unsigned int cold_thres)
{
        struct damos_access_pattern pattern = damon_lru_sort_stub_pattern;

        pattern.max_nr_accesses = 0;
        pattern.min_age_region = cold_thres;
        return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_DEPRIO);
}

static int damon_lru_sort_add_quota_goals(struct damos *hot_scheme,
                struct damos *cold_scheme)
{
        struct damos_quota_goal *goal;

        if (!active_mem_bp)
                return 0;
        goal = damos_new_quota_goal(DAMOS_QUOTA_ACTIVE_MEM_BP, active_mem_bp);
        if (!goal)
                return -ENOMEM;
        damos_add_quota_goal(&hot_scheme->quota, goal);
        /* aim 0.2 % goal conflict, to keep little ping pong */
        goal = damos_new_quota_goal(DAMOS_QUOTA_INACTIVE_MEM_BP,
                        10000 - active_mem_bp + 2);
        if (!goal)
                return -ENOMEM;
        damos_add_quota_goal(&cold_scheme->quota, goal);
        return 0;
}

static int damon_lru_sort_add_filters(struct damos *hot_scheme,
                struct damos *cold_scheme)
{
        struct damos_filter *filter;

        if (!filter_young_pages)
                return 0;

        /* disallow prioritizing not-young pages */
        filter = damos_new_filter(DAMOS_FILTER_TYPE_YOUNG, false, false);
        if (!filter)
                return -ENOMEM;
        damos_add_filter(hot_scheme, filter);

        /* disabllow de-prioritizing young pages */
        filter = damos_new_filter(DAMOS_FILTER_TYPE_YOUNG, true, false);
        if (!filter)
                return -ENOMEM;
        damos_add_filter(cold_scheme, filter);
        return 0;
}

static int damon_lru_sort_apply_parameters(void)
{
        struct damon_ctx *param_ctx;
        struct damon_target *param_target;
        struct damon_attrs attrs;
        struct damos *hot_scheme, *cold_scheme;
        unsigned int hot_thres, cold_thres;
        int err;

        err = damon_modules_new_paddr_ctx_target(&param_ctx, &param_target);
        if (err)
                return err;

        /*
         * If monitor_region_start/end are unset, always silently
         * reset addr_unit to 1.
         */
        if (!monitor_region_start && !monitor_region_end)
                addr_unit = 1;
        param_ctx->addr_unit = addr_unit;
        param_ctx->min_region_sz = max(DAMON_MIN_REGION_SZ / addr_unit, 1);

        if (!damon_lru_sort_mon_attrs.sample_interval) {
                err = -EINVAL;
                goto out;
        }

        attrs = damon_lru_sort_mon_attrs;
        if (autotune_monitoring_intervals) {
                attrs.sample_interval = 5000;
                attrs.aggr_interval = 100000;
                attrs.intervals_goal.access_bp = 40;
                attrs.intervals_goal.aggrs = 3;
                attrs.intervals_goal.min_sample_us = 5000;
                attrs.intervals_goal.max_sample_us = 10 * 1000 * 1000;
        }
        err = damon_set_attrs(param_ctx, &attrs);
        if (err)
                goto out;

        err = -ENOMEM;
        hot_thres = damon_max_nr_accesses(&attrs) *
                hot_thres_access_freq / 1000;
        hot_scheme = damon_lru_sort_new_hot_scheme(hot_thres);
        if (!hot_scheme)
                goto out;

        cold_thres = cold_min_age / attrs.aggr_interval;
        cold_scheme = damon_lru_sort_new_cold_scheme(cold_thres);
        if (!cold_scheme) {
                damon_destroy_scheme(hot_scheme);
                goto out;
        }

        damon_set_schemes(param_ctx, &hot_scheme, 1);
        damon_add_scheme(param_ctx, cold_scheme);

        err = damon_lru_sort_add_quota_goals(hot_scheme, cold_scheme);
        if (err)
                goto out;
        err = damon_lru_sort_add_filters(hot_scheme, cold_scheme);
        if (err)
                goto out;

        err = damon_set_region_biggest_system_ram_default(param_target,
                                        &monitor_region_start,
                                        &monitor_region_end,
                                        param_ctx->min_region_sz);
        if (err)
                goto out;
        err = damon_commit_ctx(ctx, param_ctx);
out:
        damon_destroy_ctx(param_ctx);
        return err;
}

static int damon_lru_sort_handle_commit_inputs(void)
{
        int err;

        if (!commit_inputs)
                return 0;

        err = damon_lru_sort_apply_parameters();
        commit_inputs = false;
        return err;
}

static int damon_lru_sort_damon_call_fn(void *arg)
{
        struct damon_ctx *c = arg;
        struct damos *s;

        /* update the stats parameter */
        damon_for_each_scheme(s, c) {
                if (s->action == DAMOS_LRU_PRIO)
                        damon_lru_sort_hot_stat = s->stat;
                else if (s->action == DAMOS_LRU_DEPRIO)
                        damon_lru_sort_cold_stat = s->stat;
        }

        return damon_lru_sort_handle_commit_inputs();
}

static struct damon_call_control call_control = {
        .fn = damon_lru_sort_damon_call_fn,
        .repeat = true,
};

static int damon_lru_sort_turn(bool on)
{
        int err;

        if (!on) {
                err = damon_stop(&ctx, 1);
                if (!err)
                        kdamond_pid = -1;
                return err;
        }

        err = damon_lru_sort_apply_parameters();
        if (err)
                return err;

        err = damon_start(&ctx, 1, true);
        if (err)
                return err;
        kdamond_pid = damon_kdamond_pid(ctx);
        if (kdamond_pid < 0)
                return kdamond_pid;
        return damon_call(ctx, &call_control);
}

static int damon_lru_sort_addr_unit_store(const char *val,
                const struct kernel_param *kp)
{
        unsigned long input_addr_unit;
        int err = kstrtoul(val, 0, &input_addr_unit);

        if (err)
                return err;
        if (!input_addr_unit)
                return -EINVAL;

        addr_unit = input_addr_unit;
        return 0;
}

static const struct kernel_param_ops addr_unit_param_ops = {
        .set = damon_lru_sort_addr_unit_store,
        .get = param_get_ulong,
};

module_param_cb(addr_unit, &addr_unit_param_ops, &addr_unit, 0600);
MODULE_PARM_DESC(addr_unit,
        "Scale factor for DAMON_LRU_SORT to ops address conversion (default: 1)");

static int damon_lru_sort_enabled_store(const char *val,
                const struct kernel_param *kp)
{
        bool is_enabled = enabled;
        bool enable;
        int err;

        err = kstrtobool(val, &enable);
        if (err)
                return err;

        if (is_enabled == enable)
                return 0;

        /* Called before init function.  The function will handle this. */
        if (!damon_initialized())
                goto set_param_out;

        err = damon_lru_sort_turn(enable);
        if (err)
                return err;

set_param_out:
        enabled = enable;
        return err;
}

static const struct kernel_param_ops enabled_param_ops = {
        .set = damon_lru_sort_enabled_store,
        .get = param_get_bool,
};

module_param_cb(enabled, &enabled_param_ops, &enabled, 0600);
MODULE_PARM_DESC(enabled,
        "Enable or disable DAMON_LRU_SORT (default: disabled)");

static int __init damon_lru_sort_init(void)
{
        int err;

        if (!damon_initialized()) {
                err = -ENOMEM;
                goto out;
        }
        err = damon_modules_new_paddr_ctx_target(&ctx, &target);
        if (err)
                goto out;

        call_control.data = ctx;

        /* 'enabled' has set before this function, probably via command line */
        if (enabled)
                err = damon_lru_sort_turn(true);

out:
        if (err && enabled)
                enabled = false;
        return err;
}

module_init(damon_lru_sort_init);