lmkd: Introduce kill strategy based on zone watermarks, swap and thrashing (ad233c87) · Commits · e / os / android_system_core

lmkd/README.md

+18 −1

Original line number	Diff line number	Diff line
		@@ -60,6 +60,23 @@ properties:
		any eligible task (fast decision). Default = false

		ro.lmk.kill_timeout_ms: duration in ms after a kill when no additional
		kill will be done, Default = 0 (disabled)
		kill will be done. Default = 0 (disabled)

		ro.lmk.debug: enable lmkd debug logs, Default = false

		ro.lmk.swap_free_low_percentage: level of free swap as a percentage of the
		total swap space used as a threshold to consider
		the system as swap space starved. Default for
		low-RAM devices = 10, for high-end devices = 20

		ro.lmk.thrashing_limit: number of workingset refaults as a percentage of
		the file-backed pagecache size used as a threshold
		to consider system thrashing its pagecache.
		Default for low-RAM devices = 30, for high-end
		devices = 100

		ro.lmk.thrashing_limit_decay: thrashing threshold decay expressed as a
		percentage of the original threshold used to lower
		the threshold when system does not recover even
		after a kill. Default for low-RAM devices = 50,
		for high-end devices = 10

lmkd/lmkd.c

+335 −7

Original line number	Diff line number	Diff line
		@@ -79,6 +79,7 @@
		#define MEMCG_MEMORYSW_USAGE "/dev/memcg/memory.memsw.usage_in_bytes"
		#define ZONEINFO_PATH "/proc/zoneinfo"
		#define MEMINFO_PATH "/proc/meminfo"
		#define VMSTAT_PATH "/proc/vmstat"
		#define PROC_STATUS_TGID_FIELD "Tgid:"
		#define LINE_MAX 128

		@@ -110,13 +111,29 @@
		* PSI_WINDOW_SIZE_MS after the event happens.
		*/
		#define PSI_WINDOW_SIZE_MS 1000
		/* Polling period after initial PSI signal */
		#define PSI_POLL_PERIOD_MS 10
		/* Polling period after PSI signal when pressure is high */
		#define PSI_POLL_PERIOD_SHORT_MS 10
		/* Polling period after PSI signal when pressure is low */
		#define PSI_POLL_PERIOD_LONG_MS 100

		#define min(a, b) (((a) < (b)) ? (a) : (b))
		#define max(a, b) (((a) > (b)) ? (a) : (b))

		#define FAIL_REPORT_RLIMIT_MS 1000

		/*
		* System property defaults
		*/
		/* ro.lmk.swap_free_low_percentage property defaults */
		#define DEF_LOW_SWAP_LOWRAM 10
		#define DEF_LOW_SWAP 20
		/* ro.lmk.thrashing_limit property defaults */
		#define DEF_THRASHING_LOWRAM 30
		#define DEF_THRASHING 100
		/* ro.lmk.thrashing_limit_decay property defaults */
		#define DEF_THRASHING_DECAY_LOWRAM 50
		#define DEF_THRASHING_DECAY 10

		/* default to old in-kernel interface if no memory pressure events */
		static bool use_inkernel_interface = true;
		static bool has_inkernel_module;
		@@ -157,6 +174,8 @@ static unsigned long kill_timeout_ms;
		static bool use_minfree_levels;
		static bool per_app_memcg;
		static int swap_free_low_percentage;
		static int thrashing_limit_pct;
		static int thrashing_limit_decay_pct;
		static bool use_psi_monitors = false;
		static struct psi_threshold psi_thresholds[VMPRESS_LEVEL_COUNT] = {
		{ PSI_SOME, 70 }, /* 70ms out of 1sec for partial stall */
		@@ -390,6 +409,41 @@ union meminfo {
		int64_t arr[MI_FIELD_COUNT];
		};

		/* Fields to parse in /proc/vmstat */
		enum vmstat_field {
		VS_FREE_PAGES,
		VS_INACTIVE_FILE,
		VS_ACTIVE_FILE,
		VS_WORKINGSET_REFAULT,
		VS_PGSCAN_KSWAPD,
		VS_PGSCAN_DIRECT,
		VS_PGSCAN_DIRECT_THROTTLE,
		VS_FIELD_COUNT
		};

		static const char* const vmstat_field_names[MI_FIELD_COUNT] = {
		"nr_free_pages",
		"nr_inactive_file",
		"nr_active_file",
		"workingset_refault",
		"pgscan_kswapd",
		"pgscan_direct",
		"pgscan_direct_throttle",
		};

		union vmstat {
		struct {
		int64_t nr_free_pages;
		int64_t nr_inactive_file;
		int64_t nr_active_file;
		int64_t workingset_refault;
		int64_t pgscan_kswapd;
		int64_t pgscan_direct;
		int64_t pgscan_direct_throttle;
		} field;
		int64_t arr[VS_FIELD_COUNT];
		};

		enum field_match_result {
		NO_MATCH,
		PARSE_FAIL,
		@@ -445,6 +499,10 @@ static long page_k;
		static char* proc_get_name(int pid);
		static void poll_kernel();

		static int clamp(int low, int high, int value) {
		return max(min(value, high), low);
		}

		static bool parse_int64(const char* str, int64_t* ret) {
		char* endptr;
		long long val = strtoll(str, &endptr, 10);
		@@ -1248,7 +1306,7 @@ static int memory_stat_from_procfs(struct memory_stat* mem_st, int pid) {
		#endif

		/*
		* /prop/zoneinfo parsing routines
		* /proc/zoneinfo parsing routines
		* Expected file format is:
		*
		* Node <node_id>, zone <zone_name>
		@@ -1442,7 +1500,7 @@ static int zoneinfo_parse(struct zoneinfo *zi) {
		return 0;
		}

		/* /prop/meminfo parsing routines */
		/* /proc/meminfo parsing routines */
		static bool meminfo_parse_line(char line, union meminfo mi) {
		char *cp = line;
		char *ap;
		@@ -1497,6 +1555,59 @@ static int meminfo_parse(union meminfo *mi) {
		return 0;
		}

		/* /proc/vmstat parsing routines */
		static bool vmstat_parse_line(char line, union vmstat vs) {
		char *cp;
		char *ap;
		char *save_ptr;
		int64_t val;
		int field_idx;
		enum field_match_result match_res;

		cp = strtok_r(line, " ", &save_ptr);
		if (!cp) {
		return false;
		}

		ap = strtok_r(NULL, " ", &save_ptr);
		if (!ap) {
		return false;
		}

		match_res = match_field(cp, ap, vmstat_field_names, VS_FIELD_COUNT,
		&val, &field_idx);
		if (match_res == PARSE_SUCCESS) {
		vs->arr[field_idx] = val;
		}
		return (match_res != PARSE_FAIL);
		}

		static int vmstat_parse(union vmstat *vs) {
		static struct reread_data file_data = {
		.filename = VMSTAT_PATH,
		.fd = -1,
		};
		char *buf;
		char *save_ptr;
		char *line;

		memset(vs, 0, sizeof(union vmstat));

		if ((buf = reread_file(&file_data)) == NULL) {
		return -1;
		}

		for (line = strtok_r(buf, "\n", &save_ptr); line;
		line = strtok_r(NULL, "\n", &save_ptr)) {
		if (!vmstat_parse_line(line, vs)) {
		ALOGE("%s parse error", file_data.filename);
		return -1;
		}
		}

		return 0;
		}

		static void meminfo_log(union meminfo *mi) {
		for (int field_idx = 0; field_idx < MI_FIELD_COUNT; field_idx++) {
		android_log_write_int32(ctx, (int32_t)min(mi->arr[field_idx] * page_k, INT32_MAX));
		@@ -1833,6 +1944,219 @@ static bool is_kill_pending(void) {
		return false;
		}

		enum zone_watermark {
		WMARK_MIN = 0,
		WMARK_LOW,
		WMARK_HIGH,
		WMARK_NONE
		};

		/*
		* Returns lowest breached watermark or WMARK_NONE.
		*/
		static enum zone_watermark get_lowest_watermark(struct zoneinfo *zi)
		{
		enum zone_watermark wmark = WMARK_NONE;

		for (int node_idx = 0; node_idx < zi->node_count; node_idx++) {
		struct zoneinfo_node *node = &zi->nodes[node_idx];

		for (int zone_idx = 0; zone_idx < node->zone_count; zone_idx++) {
		struct zoneinfo_zone *zone = &node->zones[zone_idx];
		int zone_free_mem;

		if (!zone->fields.field.present) {
		continue;
		}

		zone_free_mem = zone->fields.field.nr_free_pages - zone->fields.field.nr_free_cma;
		if (zone_free_mem > zone->max_protection + zone->fields.field.high) {
		continue;
		}
		if (zone_free_mem > zone->max_protection + zone->fields.field.low) {
		if (wmark > WMARK_HIGH) wmark = WMARK_HIGH;
		continue;
		}
		if (zone_free_mem > zone->max_protection + zone->fields.field.min) {
		if (wmark > WMARK_LOW) wmark = WMARK_LOW;
		continue;
		}
		wmark = WMARK_MIN;
		}
		}

		return wmark;
		}

		static void mp_event_psi(int data, uint32_t events, struct polling_params *poll_params) {
		enum kill_reasons {
		NONE = -1, /* To denote no kill condition */
		PRESSURE_AFTER_KILL = 0,
		NOT_RESPONDING,
		LOW_SWAP_AND_THRASHING,
		LOW_MEM_AND_SWAP,
		LOW_MEM_AND_THRASHING,
		DIRECT_RECL_AND_THRASHING,
		KILL_REASON_COUNT
		};
		enum reclaim_state {
		NO_RECLAIM = 0,
		KSWAPD_RECLAIM,
		DIRECT_RECLAIM,
		};
		static int64_t init_ws_refault;
		static int64_t base_file_lru;
		static int64_t init_pgscan_kswapd;
		static int64_t init_pgscan_direct;
		static int64_t swap_low_threshold;
		static bool killing;
		static int thrashing_limit;
		static bool in_reclaim;

		union meminfo mi;
		union vmstat vs;
		struct zoneinfo zi;
		struct timespec curr_tm;
		int64_t thrashing = 0;
		bool swap_is_low = false;
		enum vmpressure_level level = (enum vmpressure_level)data;
		enum kill_reasons kill_reason = NONE;
		bool cycle_after_kill = false;
		enum reclaim_state reclaim = NO_RECLAIM;
		enum zone_watermark wmark = WMARK_NONE;

		/* Skip while still killing a process */
		if (is_kill_pending()) {
		/* TODO: replace this quick polling with pidfd polling if kernel supports */
		goto no_kill;
		}

		if (clock_gettime(CLOCK_MONOTONIC_COARSE, &curr_tm) != 0) {
		ALOGE("Failed to get current time");
		return;
		}

		if (vmstat_parse(&vs) < 0) {
		ALOGE("Failed to parse vmstat!");
		return;
		}

		if (meminfo_parse(&mi) < 0) {
		ALOGE("Failed to parse meminfo!");
		return;
		}

		/* Reset states after process got killed */
		if (killing) {
		killing = false;
		cycle_after_kill = true;
		/* Reset file-backed pagecache size and refault amounts after a kill */
		base_file_lru = vs.field.nr_inactive_file + vs.field.nr_active_file;
		init_ws_refault = vs.field.workingset_refault;
		}

		/* Check free swap levels */
		if (swap_free_low_percentage) {
		if (!swap_low_threshold) {
		swap_low_threshold = mi.field.total_swap * swap_free_low_percentage / 100;
		}
		swap_is_low = mi.field.free_swap < swap_low_threshold;
		}

		/* Identify reclaim state */
		if (vs.field.pgscan_direct > init_pgscan_direct) {
		init_pgscan_direct = vs.field.pgscan_direct;
		init_pgscan_kswapd = vs.field.pgscan_kswapd;
		reclaim = DIRECT_RECLAIM;
		} else if (vs.field.pgscan_kswapd > init_pgscan_kswapd) {
		init_pgscan_kswapd = vs.field.pgscan_kswapd;
		reclaim = KSWAPD_RECLAIM;
		} else {
		in_reclaim = false;
		/* Skip if system is not reclaiming */
		goto no_kill;
		}

		if (!in_reclaim) {
		/* Record file-backed pagecache size when entering reclaim cycle */
		base_file_lru = vs.field.nr_inactive_file + vs.field.nr_active_file;
		init_ws_refault = vs.field.workingset_refault;
		thrashing_limit = thrashing_limit_pct;
		} else {
		/* Calculate what % of the file-backed pagecache refaulted so far */
		thrashing = (vs.field.workingset_refault - init_ws_refault) * 100 / base_file_lru;
		}
		in_reclaim = true;

		/* Find out which watermark is breached if any */
		if (zoneinfo_parse(&zi) < 0) {
		ALOGE("Failed to parse zoneinfo!");
		return;
		}
		wmark = get_lowest_watermark(&zi);

		/*
		* TODO: move this logic into a separate function
		* Decide if killing a process is necessary and record the reason
		*/
		if (cycle_after_kill && wmark < WMARK_LOW) {
		/*
		* Prevent kills not freeing enough memory which might lead to OOM kill.
		* This might happen when a process is consuming memory faster than reclaim can
		* free even after a kill. Mostly happens when running memory stress tests.
		*/
		kill_reason = PRESSURE_AFTER_KILL;
		} else if (level == VMPRESS_LEVEL_CRITICAL && events != 0) {
		/*
		* Device is too busy reclaiming memory which might lead to ANR.
		* Critical level is triggered when PSI complete stall (all tasks are blocked because
		* of the memory congestion) breaches the configured threshold.
		*/
		kill_reason = NOT_RESPONDING;
		} else if (swap_is_low && thrashing > thrashing_limit_pct) {
		/* Page cache is thrashing while swap is low */
		kill_reason = LOW_SWAP_AND_THRASHING;
		} else if (swap_is_low && wmark < WMARK_HIGH) {
		/* Both free memory and swap are low */
		kill_reason = LOW_MEM_AND_SWAP;
		} else if (wmark < WMARK_HIGH && thrashing > thrashing_limit) {
		/* Page cache is thrashing while memory is low */
		thrashing_limit = (thrashing_limit * (100 - thrashing_limit_decay_pct)) / 100;
		kill_reason = LOW_MEM_AND_THRASHING;
		} else if (reclaim == DIRECT_RECLAIM && thrashing > thrashing_limit) {
		/* Page cache is thrashing while in direct reclaim (mostly happens on lowram devices) */
		thrashing_limit = (thrashing_limit * (100 - thrashing_limit_decay_pct)) / 100;
		kill_reason = DIRECT_RECL_AND_THRASHING;
		}

		/* Kill a process if necessary */
		if (kill_reason != NONE) {
		int pages_freed = find_and_kill_process(0);
		killing = (pages_freed > 0);
		meminfo_log(&mi);
		}

		no_kill:
		/*
		* Start polling after initial PSI event;
		* extend polling while device is in direct reclaim or process is being killed;
		* do not extend when kswapd reclaims because that might go on for a long time
		* without causing memory pressure
		*/
		if (events \|\| killing \|\| reclaim == DIRECT_RECLAIM) {
		poll_params->update = POLLING_START;
		}

		/* Decide the polling interval */
		if (swap_is_low \|\| killing) {
		/* Fast polling during and after a kill or when swap is low */
		poll_params->polling_interval_ms = PSI_POLL_PERIOD_SHORT_MS;
		} else {
		/* By default use long intervals */
		poll_params->polling_interval_ms = PSI_POLL_PERIOD_LONG_MS;
		}
		}

		static void mp_event_common(int data, uint32_t events, struct polling_params *poll_params) {
		int ret;
		unsigned long long evcount;
		@@ -1881,7 +2205,7 @@ static void mp_event_common(int data, uint32_t events, struct polling_params *po
		if (use_psi_monitors && events) {
		/* Override polling params only if current event is more critical */
		if (!poll_params->poll_handler \|\| data > poll_params->poll_handler->data) {
		poll_params->polling_interval_ms = PSI_POLL_PERIOD_MS;
		poll_params->polling_interval_ms = PSI_POLL_PERIOD_SHORT_MS;
		poll_params->update = POLLING_START;
		}
		}
		@@ -2483,8 +2807,12 @@ int main(int argc __unused, char **argv __unused) {
		property_get_bool("ro.lmk.use_minfree_levels", false);
		per_app_memcg =
		property_get_bool("ro.config.per_app_memcg", low_ram_device);
		swap_free_low_percentage =
		property_get_int32("ro.lmk.swap_free_low_percentage", 10);
		swap_free_low_percentage = clamp(0, 100, property_get_int32("ro.lmk.swap_free_low_percentage",
		low_ram_device ? DEF_LOW_SWAP_LOWRAM : DEF_LOW_SWAP));
		thrashing_limit_pct = max(0, property_get_int32("ro.lmk.thrashing_limit",
		low_ram_device ? DEF_THRASHING_LOWRAM : DEF_THRASHING));
		thrashing_limit_decay_pct = clamp(0, 100, property_get_int32("ro.lmk.thrashing_limit_decay",
		low_ram_device ? DEF_THRASHING_DECAY_LOWRAM : DEF_THRASHING_DECAY));

		ctx = create_android_logger(MEMINFO_LOG_TAG);