linux/mm/damon/lru_sort.c
SeongJae Park 44063f125a mm/damon/lru_sort: avoid divide-by-zero in hot threshold calculation
When calculating the hotness threshold for lru_prio scheme of
DAMON_LRU_SORT, the module divides some values by the maximum nr_accesses.
However, due to the type of the related variables, simple division-based
calculation of the divisor can return zero.  As a result, divide-by-zero
is possible.  Fix it by using damon_max_nr_accesses(), which handles the
case.

Link: https://lkml.kernel.org/r/20231019194924.100347-5-sj@kernel.org
Fixes: 40e983cca9 ("mm/damon: introduce DAMON-based LRU-lists Sorting")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Jakub Acs <acsjakub@amazon.de>
Cc: <stable@vger.kernel.org>	[6.0+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-10-25 16:47:15 -07:00

324 lines
8.6 KiB
C

// 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 parametrs 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);
/*
* 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 = 0,
};
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);
/*
* 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);
}
/* 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_apply_parameters(void)
{
struct damos *scheme;
unsigned int hot_thres, cold_thres;
int err = 0;
err = damon_set_attrs(ctx, &damon_lru_sort_mon_attrs);
if (err)
return err;
hot_thres = damon_max_nr_accesses(&damon_lru_sort_mon_attrs) *
hot_thres_access_freq / 1000;
scheme = damon_lru_sort_new_hot_scheme(hot_thres);
if (!scheme)
return -ENOMEM;
damon_set_schemes(ctx, &scheme, 1);
cold_thres = cold_min_age / damon_lru_sort_mon_attrs.aggr_interval;
scheme = damon_lru_sort_new_cold_scheme(cold_thres);
if (!scheme)
return -ENOMEM;
damon_add_scheme(ctx, scheme);
return damon_set_region_biggest_system_ram_default(target,
&monitor_region_start,
&monitor_region_end);
}
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 = ctx->kdamond->pid;
return 0;
}
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 (!ctx)
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 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_after_aggregation(struct damon_ctx *c)
{
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 int damon_lru_sort_after_wmarks_check(struct damon_ctx *c)
{
return damon_lru_sort_handle_commit_inputs();
}
static int __init damon_lru_sort_init(void)
{
int err = damon_modules_new_paddr_ctx_target(&ctx, &target);
if (err)
return err;
ctx->callback.after_wmarks_check = damon_lru_sort_after_wmarks_check;
ctx->callback.after_aggregation = damon_lru_sort_after_aggregation;
/* 'enabled' has set before this function, probably via command line */
if (enabled)
err = damon_lru_sort_turn(true);
return err;
}
module_init(damon_lru_sort_init);