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357 lines
10 KiB
C
357 lines
10 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* DAMON-based page reclamation
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*
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* Author: SeongJae Park <sj@kernel.org>
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*/
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#define pr_fmt(fmt) "damon-reclaim: " fmt
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#include <linux/damon.h>
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#include <linux/ioport.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/workqueue.h>
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#ifdef MODULE_PARAM_PREFIX
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#undef MODULE_PARAM_PREFIX
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#endif
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#define MODULE_PARAM_PREFIX "damon_reclaim."
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/*
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* Enable or disable DAMON_RECLAIM.
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*
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* You can enable DAMON_RCLAIM by setting the value of this parameter as ``Y``.
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* Setting it as ``N`` disables DAMON_RECLAIM. Note that DAMON_RECLAIM could
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* do no real monitoring and reclamation due to the watermarks-based activation
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* condition. Refer to below descriptions for the watermarks parameter for
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* this.
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*/
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static bool enabled __read_mostly;
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module_param(enabled, bool, 0600);
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/*
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* Time threshold for cold memory regions identification in microseconds.
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*
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* If a memory region is not accessed for this or longer time, DAMON_RECLAIM
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* identifies the region as cold, and reclaims. 120 seconds by default.
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*/
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static unsigned long min_age __read_mostly = 120000000;
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module_param(min_age, ulong, 0600);
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/*
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* Limit of time for trying the reclamation in milliseconds.
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*
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* DAMON_RECLAIM tries to use only up to this time within a time window
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* (quota_reset_interval_ms) for trying reclamation of cold pages. This can be
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* used for limiting CPU consumption of DAMON_RECLAIM. If the value is zero,
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* the limit is disabled.
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*
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* 10 ms by default.
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*/
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static unsigned long quota_ms __read_mostly = 10;
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module_param(quota_ms, ulong, 0600);
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/*
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* Limit of size of memory for the reclamation in bytes.
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*
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* DAMON_RECLAIM charges amount of memory which it tried to reclaim within a
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* time window (quota_reset_interval_ms) and makes no more than this limit is
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* tried. This can be used for limiting consumption of CPU and IO. If this
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* value is zero, the limit is disabled.
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*
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* 128 MiB by default.
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*/
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static unsigned long quota_sz __read_mostly = 128 * 1024 * 1024;
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module_param(quota_sz, ulong, 0600);
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/*
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* The time/size quota charge reset interval in milliseconds.
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*
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* The charge reset interval for the quota of time (quota_ms) and size
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* (quota_sz). That is, DAMON_RECLAIM does not try reclamation for more than
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* quota_ms milliseconds or quota_sz bytes within quota_reset_interval_ms
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* milliseconds.
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*
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* 1 second by default.
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*/
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static unsigned long quota_reset_interval_ms __read_mostly = 1000;
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module_param(quota_reset_interval_ms, ulong, 0600);
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/*
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* The watermarks check time interval in microseconds.
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*
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* Minimal time to wait before checking the watermarks, when DAMON_RECLAIM is
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* enabled but inactive due to its watermarks rule. 5 seconds by default.
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*/
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static unsigned long wmarks_interval __read_mostly = 5000000;
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module_param(wmarks_interval, ulong, 0600);
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/*
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* Free memory rate (per thousand) for the high watermark.
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*
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* If free memory of the system in bytes per thousand bytes is higher than
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* this, DAMON_RECLAIM becomes inactive, so it does nothing but periodically
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* checks the watermarks. 500 (50%) by default.
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*/
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static unsigned long wmarks_high __read_mostly = 500;
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module_param(wmarks_high, ulong, 0600);
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/*
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* Free memory rate (per thousand) for the middle watermark.
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*
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* If free memory of the system in bytes per thousand bytes is between this and
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* the low watermark, DAMON_RECLAIM becomes active, so starts the monitoring
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* and the reclaiming. 400 (40%) by default.
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*/
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static unsigned long wmarks_mid __read_mostly = 400;
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module_param(wmarks_mid, ulong, 0600);
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/*
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* Free memory rate (per thousand) for the low watermark.
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*
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* If free memory of the system in bytes per thousand bytes is lower than this,
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* DAMON_RECLAIM becomes inactive, so it does nothing but periodically checks
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* the watermarks. In the case, the system falls back to the LRU-based page
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* granularity reclamation logic. 200 (20%) by default.
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*/
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static unsigned long wmarks_low __read_mostly = 200;
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module_param(wmarks_low, ulong, 0600);
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/*
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* Sampling interval for the monitoring in microseconds.
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*
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* The sampling interval of DAMON for the cold memory monitoring. Please refer
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* to the DAMON documentation for more detail. 5 ms by default.
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*/
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static unsigned long sample_interval __read_mostly = 5000;
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module_param(sample_interval, ulong, 0600);
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/*
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* Aggregation interval for the monitoring in microseconds.
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*
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* The aggregation interval of DAMON for the cold memory monitoring. Please
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* refer to the DAMON documentation for more detail. 100 ms by default.
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*/
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static unsigned long aggr_interval __read_mostly = 100000;
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module_param(aggr_interval, ulong, 0600);
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/*
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* Minimum number of monitoring regions.
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*
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* The minimal number of monitoring regions of DAMON for the cold memory
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* monitoring. This can be used to set lower-bound of the monitoring quality.
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* But, setting this too high could result in increased monitoring overhead.
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* Please refer to the DAMON documentation for more detail. 10 by default.
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*/
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static unsigned long min_nr_regions __read_mostly = 10;
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module_param(min_nr_regions, ulong, 0600);
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/*
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* Maximum number of monitoring regions.
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*
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* The maximum number of monitoring regions of DAMON for the cold memory
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* monitoring. This can be used to set upper-bound of the monitoring overhead.
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* However, setting this too low could result in bad monitoring quality.
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* Please refer to the DAMON documentation for more detail. 1000 by default.
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*/
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static unsigned long max_nr_regions __read_mostly = 1000;
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module_param(max_nr_regions, ulong, 0600);
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/*
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* Start of the target memory region in physical address.
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*
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* The start physical address of memory region that DAMON_RECLAIM will do work
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* against. By default, biggest System RAM is used as the region.
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*/
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static unsigned long monitor_region_start __read_mostly;
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module_param(monitor_region_start, ulong, 0600);
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/*
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* End of the target memory region in physical address.
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*
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* The end physical address of memory region that DAMON_RECLAIM will do work
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* against. By default, biggest System RAM is used as the region.
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*/
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static unsigned long monitor_region_end __read_mostly;
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module_param(monitor_region_end, ulong, 0600);
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/*
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* PID of the DAMON thread
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*
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* If DAMON_RECLAIM is enabled, this becomes the PID of the worker thread.
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* Else, -1.
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*/
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static int kdamond_pid __read_mostly = -1;
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module_param(kdamond_pid, int, 0400);
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static struct damon_ctx *ctx;
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static struct damon_target *target;
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struct damon_reclaim_ram_walk_arg {
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unsigned long start;
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unsigned long end;
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};
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static int walk_system_ram(struct resource *res, void *arg)
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{
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struct damon_reclaim_ram_walk_arg *a = arg;
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if (a->end - a->start < res->end - res->start) {
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a->start = res->start;
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a->end = res->end;
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}
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return 0;
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}
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/*
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* Find biggest 'System RAM' resource and store its start and end address in
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* @start and @end, respectively. If no System RAM is found, returns false.
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*/
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static bool get_monitoring_region(unsigned long *start, unsigned long *end)
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{
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struct damon_reclaim_ram_walk_arg arg = {};
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walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram);
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if (arg.end <= arg.start)
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return false;
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*start = arg.start;
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*end = arg.end;
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return true;
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}
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static struct damos *damon_reclaim_new_scheme(void)
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{
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struct damos_watermarks wmarks = {
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.metric = DAMOS_WMARK_FREE_MEM_RATE,
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.interval = wmarks_interval,
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.high = wmarks_high,
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.mid = wmarks_mid,
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.low = wmarks_low,
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};
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struct damos_quota quota = {
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/*
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* Do not try reclamation for more than quota_ms milliseconds
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* or quota_sz bytes within quota_reset_interval_ms.
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*/
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.ms = quota_ms,
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.sz = quota_sz,
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.reset_interval = quota_reset_interval_ms,
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/* Within the quota, page out older regions first. */
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.weight_sz = 0,
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.weight_nr_accesses = 0,
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.weight_age = 1
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};
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struct damos *scheme = damon_new_scheme(
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/* Find regions having PAGE_SIZE or larger size */
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PAGE_SIZE, ULONG_MAX,
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/* and not accessed at all */
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0, 0,
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/* for min_age or more micro-seconds, and */
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min_age / aggr_interval, UINT_MAX,
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/* page out those, as soon as found */
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DAMOS_PAGEOUT,
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/* under the quota. */
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"a,
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/* (De)activate this according to the watermarks. */
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&wmarks);
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return scheme;
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}
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static int damon_reclaim_turn(bool on)
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{
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struct damon_region *region;
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struct damos *scheme;
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int err;
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if (!on) {
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err = damon_stop(&ctx, 1);
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if (!err)
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kdamond_pid = -1;
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return err;
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}
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err = damon_set_attrs(ctx, sample_interval, aggr_interval, 0,
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min_nr_regions, max_nr_regions);
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if (err)
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return err;
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if (monitor_region_start > monitor_region_end)
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return -EINVAL;
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if (!monitor_region_start && !monitor_region_end &&
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!get_monitoring_region(&monitor_region_start,
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&monitor_region_end))
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return -EINVAL;
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/* DAMON will free this on its own when finish monitoring */
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region = damon_new_region(monitor_region_start, monitor_region_end);
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if (!region)
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return -ENOMEM;
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damon_add_region(region, target);
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/* Will be freed by 'damon_set_schemes()' below */
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scheme = damon_reclaim_new_scheme();
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if (!scheme) {
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err = -ENOMEM;
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goto free_region_out;
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}
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err = damon_set_schemes(ctx, &scheme, 1);
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if (err)
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goto free_scheme_out;
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err = damon_start(&ctx, 1);
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if (!err) {
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kdamond_pid = ctx->kdamond->pid;
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return 0;
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}
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free_scheme_out:
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damon_destroy_scheme(scheme);
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free_region_out:
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damon_destroy_region(region, target);
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return err;
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}
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#define ENABLE_CHECK_INTERVAL_MS 1000
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static struct delayed_work damon_reclaim_timer;
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static void damon_reclaim_timer_fn(struct work_struct *work)
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{
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static bool last_enabled;
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bool now_enabled;
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now_enabled = enabled;
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if (last_enabled != now_enabled) {
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if (!damon_reclaim_turn(now_enabled))
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last_enabled = now_enabled;
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else
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enabled = last_enabled;
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}
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schedule_delayed_work(&damon_reclaim_timer,
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msecs_to_jiffies(ENABLE_CHECK_INTERVAL_MS));
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}
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static DECLARE_DELAYED_WORK(damon_reclaim_timer, damon_reclaim_timer_fn);
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static int __init damon_reclaim_init(void)
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{
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ctx = damon_new_ctx();
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if (!ctx)
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return -ENOMEM;
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damon_pa_set_primitives(ctx);
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/* 4242 means nothing but fun */
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target = damon_new_target(4242);
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if (!target) {
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damon_destroy_ctx(ctx);
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return -ENOMEM;
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}
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damon_add_target(ctx, target);
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schedule_delayed_work(&damon_reclaim_timer, 0);
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return 0;
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}
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module_init(damon_reclaim_init);
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