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Commit 4755b72e authored by San Mehat's avatar San Mehat Committed by Greg Kroah-Hartman
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staging: android: lowmemkiller: Substantially reduce overhead during reclaim 



This patch optimizes lowmemkiller to not do any work when it has an outstanding
kill-request. This greatly reduces the pressure on the task_list lock
(improving interactivity), as well as improving the vmscan performance
when under heavy memory pressure (by up to 20x in tests).

Note: For this enhancement to work, you need CONFIG_PROFILING

Signed-off-by: default avatarSan Mehat <san@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 4964cd41

drivers/staging/android/lowmemorykiller.c

+43 −0
Original line number Diff line number Diff line
@@ -34,6 +34,8 @@ 
#include <linux/mm.h>

#include <linux/oom.h>

#include <linux/sched.h>

#include <linux/profile.h>

#include <linux/notifier.h>



static uint32_t lowmem_debug_level = 2;

static int lowmem_adj[6] = {
@@ -51,12 +53,32 @@ static size_t lowmem_minfree[6] = { 
};

static int lowmem_minfree_size = 4;



static struct task_struct *lowmem_deathpending;



#define lowmem_print(level, x...)			\

	do {						\

		if (lowmem_debug_level >= (level))	\

			printk(x);			\

	} while (0)



static int

task_notify_func(struct notifier_block *self, unsigned long val, void *data);



static struct notifier_block task_nb = {

	.notifier_call	= task_notify_func,

};



static int

task_notify_func(struct notifier_block *self, unsigned long val, void *data)

{

	struct task_struct *task = data;

	if (task == lowmem_deathpending) {

		lowmem_deathpending = NULL;

		task_handoff_unregister(&task_nb);

	}

	return NOTIFY_OK;

}



static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)

{

	struct task_struct *p;
@@ -71,6 +93,18 @@ static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask) 
	int other_free = global_page_state(NR_FREE_PAGES);

	int other_file = global_page_state(NR_FILE_PAGES);



	/*

	 * If we already have a death outstanding, then

	 * bail out right away; indicating to vmscan

	 * that we have nothing further to offer on

	 * this pass.

	 *

	 * Note: Currently you need CONFIG_PROFILING

	 * for this to work correctly.

	 */

	if (lowmem_deathpending)

		return 0;



	if (lowmem_adj_size < array_size)

		array_size = lowmem_adj_size;

	if (lowmem_minfree_size < array_size)
@@ -142,6 +176,15 @@ static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask) 
		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",

			     selected->pid, selected->comm,

			     selected_oom_adj, selected_tasksize);

		/*

		 * If CONFIG_PROFILING is off, then task_handoff_register()

		 * is a nop. In that case we don't want to stall the killer

		 * by setting lowmem_deathpending.

		 */

#ifdef CONFIG_PROFILING

		lowmem_deathpending = selected;

		task_handoff_register(&task_nb);

#endif

		force_sig(SIGKILL, selected);

		rem -= selected_tasksize;

	}