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|
// SPDX-License-Identifier: GPL-2.0
/*
* Data Access Monitor
*
* Author: SeongJae Park <sjpark@amazon.de>
*/
#define pr_fmt(fmt) "damon: " fmt
#include <linux/damon.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/random.h>
#include <linux/slab.h>
#define CREATE_TRACE_POINTS
#include <trace/events/damon.h>
#ifdef CONFIG_DAMON_KUNIT_TEST
#undef DAMON_MIN_REGION
#define DAMON_MIN_REGION 1
#endif
/* Get a random number in [l, r) */
#define damon_rand(l, r) (l + prandom_u32_max(r - l))
static DEFINE_MUTEX(damon_lock);
static int nr_running_ctxs;
/*
* Construct a damon_region struct
*
* Returns the pointer to the new struct if success, or NULL otherwise
*/
struct damon_region *damon_new_region(unsigned long start, unsigned long end)
{
struct damon_region *region;
region = kmalloc(sizeof(*region), GFP_KERNEL);
if (!region)
return NULL;
region->ar.start = start;
region->ar.end = end;
region->nr_accesses = 0;
INIT_LIST_HEAD(®ion->list);
return region;
}
/*
* Add a region between two other regions
*/
inline void damon_insert_region(struct damon_region *r,
struct damon_region *prev, struct damon_region *next,
struct damon_target *t)
{
__list_add(&r->list, &prev->list, &next->list);
t->nr_regions++;
}
void damon_add_region(struct damon_region *r, struct damon_target *t)
{
list_add_tail(&r->list, &t->regions_list);
t->nr_regions++;
}
static void damon_del_region(struct damon_region *r, struct damon_target *t)
{
list_del(&r->list);
t->nr_regions--;
}
static void damon_free_region(struct damon_region *r)
{
kfree(r);
}
void damon_destroy_region(struct damon_region *r, struct damon_target *t)
{
damon_del_region(r, t);
damon_free_region(r);
}
/*
* Construct a damon_target struct
*
* Returns the pointer to the new struct if success, or NULL otherwise
*/
struct damon_target *damon_new_target(unsigned long id)
{
struct damon_target *t;
t = kmalloc(sizeof(*t), GFP_KERNEL);
if (!t)
return NULL;
t->id = id;
t->nr_regions = 0;
INIT_LIST_HEAD(&t->regions_list);
return t;
}
void damon_add_target(struct damon_ctx *ctx, struct damon_target *t)
{
list_add_tail(&t->list, &ctx->adaptive_targets);
}
static void damon_del_target(struct damon_target *t)
{
list_del(&t->list);
}
void damon_free_target(struct damon_target *t)
{
struct damon_region *r, *next;
damon_for_each_region_safe(r, next, t)
damon_free_region(r);
kfree(t);
}
void damon_destroy_target(struct damon_target *t)
{
damon_del_target(t);
damon_free_target(t);
}
unsigned int damon_nr_regions(struct damon_target *t)
{
return t->nr_regions;
}
struct damon_ctx *damon_new_ctx(void)
{
struct damon_ctx *ctx;
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return NULL;
ctx->sample_interval = 5 * 1000;
ctx->aggr_interval = 100 * 1000;
ctx->primitive_update_interval = 60 * 1000 * 1000;
ktime_get_coarse_ts64(&ctx->last_aggregation);
ctx->last_primitive_update = ctx->last_aggregation;
mutex_init(&ctx->kdamond_lock);
ctx->min_nr_regions = 10;
ctx->max_nr_regions = 1000;
INIT_LIST_HEAD(&ctx->adaptive_targets);
return ctx;
}
static void damon_destroy_targets(struct damon_ctx *ctx)
{
struct damon_target *t, *next_t;
if (ctx->primitive.cleanup) {
ctx->primitive.cleanup(ctx);
return;
}
damon_for_each_target_safe(t, next_t, ctx)
damon_destroy_target(t);
}
void damon_destroy_ctx(struct damon_ctx *ctx)
{
damon_destroy_targets(ctx);
kfree(ctx);
}
/**
* damon_set_targets() - Set monitoring targets.
* @ctx: monitoring context
* @ids: array of target ids
* @nr_ids: number of entries in @ids
*
* This function should not be called while the kdamond is running.
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_set_targets(struct damon_ctx *ctx,
unsigned long *ids, ssize_t nr_ids)
{
ssize_t i;
struct damon_target *t, *next;
damon_destroy_targets(ctx);
for (i = 0; i < nr_ids; i++) {
t = damon_new_target(ids[i]);
if (!t) {
pr_err("Failed to alloc damon_target\n");
/* The caller should do cleanup of the ids itself */
damon_for_each_target_safe(t, next, ctx)
damon_destroy_target(t);
return -ENOMEM;
}
damon_add_target(ctx, t);
}
return 0;
}
/**
* damon_set_attrs() - Set attributes for the monitoring.
* @ctx: monitoring context
* @sample_int: time interval between samplings
* @aggr_int: time interval between aggregations
* @primitive_upd_int: time interval between monitoring primitive updates
* @min_nr_reg: minimal number of regions
* @max_nr_reg: maximum number of regions
*
* This function should not be called while the kdamond is running.
* Every time interval is in micro-seconds.
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
unsigned long aggr_int, unsigned long primitive_upd_int,
unsigned long min_nr_reg, unsigned long max_nr_reg)
{
if (min_nr_reg < 3) {
pr_err("min_nr_regions (%lu) must be at least 3\n",
min_nr_reg);
return -EINVAL;
}
if (min_nr_reg > max_nr_reg) {
pr_err("invalid nr_regions. min (%lu) > max (%lu)\n",
min_nr_reg, max_nr_reg);
return -EINVAL;
}
ctx->sample_interval = sample_int;
ctx->aggr_interval = aggr_int;
ctx->primitive_update_interval = primitive_upd_int;
ctx->min_nr_regions = min_nr_reg;
ctx->max_nr_regions = max_nr_reg;
return 0;
}
/**
* damon_nr_running_ctxs() - Return number of currently running contexts.
*/
int damon_nr_running_ctxs(void)
{
int nr_ctxs;
mutex_lock(&damon_lock);
nr_ctxs = nr_running_ctxs;
mutex_unlock(&damon_lock);
return nr_ctxs;
}
/* Returns the size upper limit for each monitoring region */
static unsigned long damon_region_sz_limit(struct damon_ctx *ctx)
{
struct damon_target *t;
struct damon_region *r;
unsigned long sz = 0;
damon_for_each_target(t, ctx) {
damon_for_each_region(r, t)
sz += r->ar.end - r->ar.start;
}
if (ctx->min_nr_regions)
sz /= ctx->min_nr_regions;
if (sz < DAMON_MIN_REGION)
sz = DAMON_MIN_REGION;
return sz;
}
static bool damon_kdamond_running(struct damon_ctx *ctx)
{
bool running;
mutex_lock(&ctx->kdamond_lock);
running = ctx->kdamond != NULL;
mutex_unlock(&ctx->kdamond_lock);
return running;
}
static int kdamond_fn(void *data);
/*
* __damon_start() - Starts monitoring with given context.
* @ctx: monitoring context
*
* This function should be called while damon_lock is hold.
*
* Return: 0 on success, negative error code otherwise.
*/
static int __damon_start(struct damon_ctx *ctx)
{
int err = -EBUSY;
mutex_lock(&ctx->kdamond_lock);
if (!ctx->kdamond) {
err = 0;
ctx->kdamond_stop = false;
ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
nr_running_ctxs);
if (IS_ERR(ctx->kdamond)) {
err = PTR_ERR(ctx->kdamond);
ctx->kdamond = 0;
}
}
mutex_unlock(&ctx->kdamond_lock);
return err;
}
/**
* damon_start() - Starts the monitorings for a given group of contexts.
* @ctxs: an array of the pointers for contexts to start monitoring
* @nr_ctxs: size of @ctxs
*
* This function starts a group of monitoring threads for a group of monitoring
* contexts. One thread per each context is created and run in parallel. The
* caller should handle synchronization between the threads by itself. If a
* group of threads that created by other 'damon_start()' call is currently
* running, this function does nothing but returns -EBUSY.
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_start(struct damon_ctx **ctxs, int nr_ctxs)
{
int i;
int err = 0;
mutex_lock(&damon_lock);
if (nr_running_ctxs) {
mutex_unlock(&damon_lock);
return -EBUSY;
}
for (i = 0; i < nr_ctxs; i++) {
err = __damon_start(ctxs[i]);
if (err)
break;
nr_running_ctxs++;
}
mutex_unlock(&damon_lock);
return err;
}
/*
* __damon_stop() - Stops monitoring of given context.
* @ctx: monitoring context
*
* Return: 0 on success, negative error code otherwise.
*/
static int __damon_stop(struct damon_ctx *ctx)
{
mutex_lock(&ctx->kdamond_lock);
if (ctx->kdamond) {
ctx->kdamond_stop = true;
mutex_unlock(&ctx->kdamond_lock);
while (damon_kdamond_running(ctx))
usleep_range(ctx->sample_interval,
ctx->sample_interval * 2);
return 0;
}
mutex_unlock(&ctx->kdamond_lock);
return -EPERM;
}
/**
* damon_stop() - Stops the monitorings for a given group of contexts.
* @ctxs: an array of the pointers for contexts to stop monitoring
* @nr_ctxs: size of @ctxs
*
* Return: 0 on success, negative error code otherwise.
*/
int damon_stop(struct damon_ctx **ctxs, int nr_ctxs)
{
int i, err = 0;
for (i = 0; i < nr_ctxs; i++) {
/* nr_running_ctxs is decremented in kdamond_fn */
err = __damon_stop(ctxs[i]);
if (err)
return err;
}
return err;
}
/*
* damon_check_reset_time_interval() - Check if a time interval is elapsed.
* @baseline: the time to check whether the interval has elapsed since
* @interval: the time interval (microseconds)
*
* See whether the given time interval has passed since the given baseline
* time. If so, it also updates the baseline to current time for next check.
*
* Return: true if the time interval has passed, or false otherwise.
*/
static bool damon_check_reset_time_interval(struct timespec64 *baseline,
unsigned long interval)
{
struct timespec64 now;
ktime_get_coarse_ts64(&now);
if ((timespec64_to_ns(&now) - timespec64_to_ns(baseline)) <
interval * 1000)
return false;
*baseline = now;
return true;
}
/*
* Check whether it is time to flush the aggregated information
*/
static bool kdamond_aggregate_interval_passed(struct damon_ctx *ctx)
{
return damon_check_reset_time_interval(&ctx->last_aggregation,
ctx->aggr_interval);
}
/*
* Reset the aggregated monitoring results ('nr_accesses' of each region).
*/
static void kdamond_reset_aggregated(struct damon_ctx *c)
{
struct damon_target *t;
damon_for_each_target(t, c) {
struct damon_region *r;
damon_for_each_region(r, t) {
trace_damon_aggregated(t, r, damon_nr_regions(t));
r->nr_accesses = 0;
}
}
}
#define sz_damon_region(r) (r->ar.end - r->ar.start)
/*
* Merge two adjacent regions into one region
*/
static void damon_merge_two_regions(struct damon_target *t,
struct damon_region *l, struct damon_region *r)
{
unsigned long sz_l = sz_damon_region(l), sz_r = sz_damon_region(r);
l->nr_accesses = (l->nr_accesses * sz_l + r->nr_accesses * sz_r) /
(sz_l + sz_r);
l->ar.end = r->ar.end;
damon_destroy_region(r, t);
}
#define diff_of(a, b) (a > b ? a - b : b - a)
/*
* Merge adjacent regions having similar access frequencies
*
* t target affected by this merge operation
* thres '->nr_accesses' diff threshold for the merge
* sz_limit size upper limit of each region
*/
static void damon_merge_regions_of(struct damon_target *t, unsigned int thres,
unsigned long sz_limit)
{
struct damon_region *r, *prev = NULL, *next;
damon_for_each_region_safe(r, next, t) {
if (prev && prev->ar.end == r->ar.start &&
diff_of(prev->nr_accesses, r->nr_accesses) <= thres &&
sz_damon_region(prev) + sz_damon_region(r) <= sz_limit)
damon_merge_two_regions(t, prev, r);
else
prev = r;
}
}
/*
* Merge adjacent regions having similar access frequencies
*
* threshold '->nr_accesses' diff threshold for the merge
* sz_limit size upper limit of each region
*
* This function merges monitoring target regions which are adjacent and their
* access frequencies are similar. This is for minimizing the monitoring
* overhead under the dynamically changeable access pattern. If a merge was
* unnecessarily made, later 'kdamond_split_regions()' will revert it.
*/
static void kdamond_merge_regions(struct damon_ctx *c, unsigned int threshold,
unsigned long sz_limit)
{
struct damon_target *t;
damon_for_each_target(t, c)
damon_merge_regions_of(t, threshold, sz_limit);
}
/*
* Split a region in two
*
* r the region to be split
* sz_r size of the first sub-region that will be made
*/
static void damon_split_region_at(struct damon_ctx *ctx,
struct damon_target *t, struct damon_region *r,
unsigned long sz_r)
{
struct damon_region *new;
new = damon_new_region(r->ar.start + sz_r, r->ar.end);
if (!new)
return;
r->ar.end = new->ar.start;
damon_insert_region(new, r, damon_next_region(r), t);
}
/* Split every region in the given target into 'nr_subs' regions */
static void damon_split_regions_of(struct damon_ctx *ctx,
struct damon_target *t, int nr_subs)
{
struct damon_region *r, *next;
unsigned long sz_region, sz_sub = 0;
int i;
damon_for_each_region_safe(r, next, t) {
sz_region = r->ar.end - r->ar.start;
for (i = 0; i < nr_subs - 1 &&
sz_region > 2 * DAMON_MIN_REGION; i++) {
/*
* Randomly select size of left sub-region to be at
* least 10 percent and at most 90% of original region
*/
sz_sub = ALIGN_DOWN(damon_rand(1, 10) *
sz_region / 10, DAMON_MIN_REGION);
/* Do not allow blank region */
if (sz_sub == 0 || sz_sub >= sz_region)
continue;
damon_split_region_at(ctx, t, r, sz_sub);
sz_region = sz_sub;
}
}
}
/*
* Split every target region into randomly-sized small regions
*
* This function splits every target region into random-sized small regions if
* current total number of the regions is equal or smaller than half of the
* user-specified maximum number of regions. This is for maximizing the
* monitoring accuracy under the dynamically changeable access patterns. If a
* split was unnecessarily made, later 'kdamond_merge_regions()' will revert
* it.
*/
static void kdamond_split_regions(struct damon_ctx *ctx)
{
struct damon_target *t;
unsigned int nr_regions = 0;
static unsigned int last_nr_regions;
int nr_subregions = 2;
damon_for_each_target(t, ctx)
nr_regions += damon_nr_regions(t);
if (nr_regions > ctx->max_nr_regions / 2)
return;
/* Maybe the middle of the region has different access frequency */
if (last_nr_regions == nr_regions &&
nr_regions < ctx->max_nr_regions / 3)
nr_subregions = 3;
damon_for_each_target(t, ctx)
damon_split_regions_of(ctx, t, nr_subregions);
last_nr_regions = nr_regions;
}
/*
* Check whether it is time to check and apply the target monitoring regions
*
* Returns true if it is.
*/
static bool kdamond_need_update_primitive(struct damon_ctx *ctx)
{
return damon_check_reset_time_interval(&ctx->last_primitive_update,
ctx->primitive_update_interval);
}
/*
* Check whether current monitoring should be stopped
*
* The monitoring is stopped when either the user requested to stop, or all
* monitoring targets are invalid.
*
* Returns true if need to stop current monitoring.
*/
static bool kdamond_need_stop(struct damon_ctx *ctx)
{
struct damon_target *t;
bool stop;
mutex_lock(&ctx->kdamond_lock);
stop = ctx->kdamond_stop;
mutex_unlock(&ctx->kdamond_lock);
if (stop)
return true;
if (!ctx->primitive.target_valid)
return false;
damon_for_each_target(t, ctx) {
if (ctx->primitive.target_valid(t))
return false;
}
return true;
}
static void set_kdamond_stop(struct damon_ctx *ctx)
{
mutex_lock(&ctx->kdamond_lock);
ctx->kdamond_stop = true;
mutex_unlock(&ctx->kdamond_lock);
}
/*
* The monitoring daemon that runs as a kernel thread
*/
static int kdamond_fn(void *data)
{
struct damon_ctx *ctx = (struct damon_ctx *)data;
struct damon_target *t;
struct damon_region *r, *next;
unsigned int max_nr_accesses = 0;
unsigned long sz_limit = 0;
mutex_lock(&ctx->kdamond_lock);
pr_debug("kdamond (%d) starts\n", ctx->kdamond->pid);
mutex_unlock(&ctx->kdamond_lock);
if (ctx->primitive.init)
ctx->primitive.init(ctx);
if (ctx->callback.before_start && ctx->callback.before_start(ctx))
set_kdamond_stop(ctx);
sz_limit = damon_region_sz_limit(ctx);
while (!kdamond_need_stop(ctx)) {
if (ctx->primitive.prepare_access_checks)
ctx->primitive.prepare_access_checks(ctx);
if (ctx->callback.after_sampling &&
ctx->callback.after_sampling(ctx))
set_kdamond_stop(ctx);
usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
if (ctx->primitive.check_accesses)
max_nr_accesses = ctx->primitive.check_accesses(ctx);
if (kdamond_aggregate_interval_passed(ctx)) {
kdamond_merge_regions(ctx,
max_nr_accesses / 10,
sz_limit);
if (ctx->callback.after_aggregation &&
ctx->callback.after_aggregation(ctx))
set_kdamond_stop(ctx);
kdamond_reset_aggregated(ctx);
kdamond_split_regions(ctx);
if (ctx->primitive.reset_aggregated)
ctx->primitive.reset_aggregated(ctx);
}
if (kdamond_need_update_primitive(ctx)) {
if (ctx->primitive.update)
ctx->primitive.update(ctx);
sz_limit = damon_region_sz_limit(ctx);
}
}
damon_for_each_target(t, ctx) {
damon_for_each_region_safe(r, next, t)
damon_destroy_region(r, t);
}
if (ctx->callback.before_terminate &&
ctx->callback.before_terminate(ctx))
set_kdamond_stop(ctx);
if (ctx->primitive.cleanup)
ctx->primitive.cleanup(ctx);
pr_debug("kdamond (%d) finishes\n", ctx->kdamond->pid);
mutex_lock(&ctx->kdamond_lock);
ctx->kdamond = NULL;
mutex_unlock(&ctx->kdamond_lock);
mutex_lock(&damon_lock);
nr_running_ctxs--;
mutex_unlock(&damon_lock);
return 0;
}
#include "core-test.h"
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