[PATCH 1/3 staging-next] android: Collect statistics from lowmemorykiller
Michal Hocko
mhocko at kernel.org
Thu Feb 9 20:54:07 UTC 2017
On Thu 09-02-17 21:07:37, Greg KH wrote:
> On Thu, Feb 09, 2017 at 08:26:41PM +0100, Michal Hocko wrote:
> > On Thu 09-02-17 14:21:45, peter enderborg wrote:
> > > This collects stats for shrinker calls and how much
> > > waste work we do within the lowmemorykiller.
> >
> > This doesn't explain why do we need this information and who is going to
> > use it. Not to mention it exports it in /proc which is considered a
> > stable user API. This is a no-go, especially for something that is still
> > lingering in the staging tree without any actuall effort to make it
> > fully supported MM feature. I am actually strongly inclined to simply
> > drop lmk from the tree completely.
>
> I thought that someone was working to get the "native" mm features to
> work properly with the lmk "feature" Do you recall if that work got
> rejected, or just never happened?
Never happened AFAIR. There were some attempts to tune the current
behavior which has been rejected for one reason or another but I am not
really aware of anybody working on moving the code from staging area.
I already have this in the to-send queue, just didn't get to post it yet
because I planned to polish the reasoning some more.
---
>From 9f871b54a387e0a7cdfaf0fa256d1440093e427c Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko at suse.com>
Date: Wed, 1 Feb 2017 10:37:30 +0100
Subject: [PATCH] staging, android: remove lowmemory killer from the tree
Lowmemory killer is sitting in the staging tree since 2008 without any
serious interest for fixing issues brought up by the MM folks. The main
objection is that the implementation is basically broken by design:
- it hooks into slab shrinker API which is not suitable for this
purpose. lowmem_count implementation just shows this nicely.
There is no scaling based on the memory pressure and no
feedback to the generic shrinker infrastructure.
- it is not reclaim context aware - no NUMA and/or memcg
awareness.
As the code stands right now it just adds a maintenance overhead when
core MM changes have to update lowmemorykiller.c as well.
Signed-off-by: Michal Hocko <mhocko at suse.com>
---
drivers/staging/android/Kconfig | 10 --
drivers/staging/android/Makefile | 1 -
drivers/staging/android/lowmemorykiller.c | 212 ------------------------------
include/linux/sched.h | 4 -
4 files changed, 227 deletions(-)
delete mode 100644 drivers/staging/android/lowmemorykiller.c
diff --git a/drivers/staging/android/Kconfig b/drivers/staging/android/Kconfig
index 6c00d6f765c6..71a50b99caff 100644
--- a/drivers/staging/android/Kconfig
+++ b/drivers/staging/android/Kconfig
@@ -14,16 +14,6 @@ config ASHMEM
It is, in theory, a good memory allocator for low-memory devices,
because it can discard shared memory units when under memory pressure.
-config ANDROID_LOW_MEMORY_KILLER
- bool "Android Low Memory Killer"
- ---help---
- Registers processes to be killed when low memory conditions, this is useful
- as there is no particular swap space on android.
-
- The registered process will kill according to the priorities in android init
- scripts (/init.rc), and it defines priority values with minimum free memory size
- for each priority.
-
source "drivers/staging/android/ion/Kconfig"
endif # if ANDROID
diff --git a/drivers/staging/android/Makefile b/drivers/staging/android/Makefile
index 7ed1be798909..7cf1564a49a5 100644
--- a/drivers/staging/android/Makefile
+++ b/drivers/staging/android/Makefile
@@ -3,4 +3,3 @@ ccflags-y += -I$(src) # needed for trace events
obj-y += ion/
obj-$(CONFIG_ASHMEM) += ashmem.o
-obj-$(CONFIG_ANDROID_LOW_MEMORY_KILLER) += lowmemorykiller.o
diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
deleted file mode 100644
index ec3b66561412..000000000000
--- a/drivers/staging/android/lowmemorykiller.c
+++ /dev/null
@@ -1,212 +0,0 @@
-/* drivers/misc/lowmemorykiller.c
- *
- * The lowmemorykiller driver lets user-space specify a set of memory thresholds
- * where processes with a range of oom_score_adj values will get killed. Specify
- * the minimum oom_score_adj values in
- * /sys/module/lowmemorykiller/parameters/adj and the number of free pages in
- * /sys/module/lowmemorykiller/parameters/minfree. Both files take a comma
- * separated list of numbers in ascending order.
- *
- * For example, write "0,8" to /sys/module/lowmemorykiller/parameters/adj and
- * "1024,4096" to /sys/module/lowmemorykiller/parameters/minfree to kill
- * processes with a oom_score_adj value of 8 or higher when the free memory
- * drops below 4096 pages and kill processes with a oom_score_adj value of 0 or
- * higher when the free memory drops below 1024 pages.
- *
- * The driver considers memory used for caches to be free, but if a large
- * percentage of the cached memory is locked this can be very inaccurate
- * and processes may not get killed until the normal oom killer is triggered.
- *
- * Copyright (C) 2007-2008 Google, Inc.
- *
- * This software is licensed under the terms of the GNU General Public
- * License version 2, as published by the Free Software Foundation, and
- * may be copied, distributed, and modified under those terms.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- */
-
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-
-#include <linux/init.h>
-#include <linux/moduleparam.h>
-#include <linux/kernel.h>
-#include <linux/mm.h>
-#include <linux/oom.h>
-#include <linux/sched.h>
-#include <linux/swap.h>
-#include <linux/rcupdate.h>
-#include <linux/profile.h>
-#include <linux/notifier.h>
-
-static u32 lowmem_debug_level = 1;
-static short lowmem_adj[6] = {
- 0,
- 1,
- 6,
- 12,
-};
-
-static int lowmem_adj_size = 4;
-static int lowmem_minfree[6] = {
- 3 * 512, /* 6MB */
- 2 * 1024, /* 8MB */
- 4 * 1024, /* 16MB */
- 16 * 1024, /* 64MB */
-};
-
-static int lowmem_minfree_size = 4;
-
-static unsigned long lowmem_deathpending_timeout;
-
-#define lowmem_print(level, x...) \
- do { \
- if (lowmem_debug_level >= (level)) \
- pr_info(x); \
- } while (0)
-
-static unsigned long lowmem_count(struct shrinker *s,
- struct shrink_control *sc)
-{
- return global_node_page_state(NR_ACTIVE_ANON) +
- global_node_page_state(NR_ACTIVE_FILE) +
- global_node_page_state(NR_INACTIVE_ANON) +
- global_node_page_state(NR_INACTIVE_FILE);
-}
-
-static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
-{
- struct task_struct *tsk;
- struct task_struct *selected = NULL;
- unsigned long rem = 0;
- int tasksize;
- int i;
- short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
- int minfree = 0;
- int selected_tasksize = 0;
- short selected_oom_score_adj;
- int array_size = ARRAY_SIZE(lowmem_adj);
- int other_free = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
- int other_file = global_node_page_state(NR_FILE_PAGES) -
- global_node_page_state(NR_SHMEM) -
- total_swapcache_pages();
-
- if (lowmem_adj_size < array_size)
- array_size = lowmem_adj_size;
- if (lowmem_minfree_size < array_size)
- array_size = lowmem_minfree_size;
- for (i = 0; i < array_size; i++) {
- minfree = lowmem_minfree[i];
- if (other_free < minfree && other_file < minfree) {
- min_score_adj = lowmem_adj[i];
- break;
- }
- }
-
- lowmem_print(3, "lowmem_scan %lu, %x, ofree %d %d, ma %hd\n",
- sc->nr_to_scan, sc->gfp_mask, other_free,
- other_file, min_score_adj);
-
- if (min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
- lowmem_print(5, "lowmem_scan %lu, %x, return 0\n",
- sc->nr_to_scan, sc->gfp_mask);
- return 0;
- }
-
- selected_oom_score_adj = min_score_adj;
-
- rcu_read_lock();
- for_each_process(tsk) {
- struct task_struct *p;
- short oom_score_adj;
-
- if (tsk->flags & PF_KTHREAD)
- continue;
-
- p = find_lock_task_mm(tsk);
- if (!p)
- continue;
-
- if (task_lmk_waiting(p) &&
- time_before_eq(jiffies, lowmem_deathpending_timeout)) {
- task_unlock(p);
- rcu_read_unlock();
- return 0;
- }
- oom_score_adj = p->signal->oom_score_adj;
- if (oom_score_adj < min_score_adj) {
- task_unlock(p);
- continue;
- }
- tasksize = get_mm_rss(p->mm);
- task_unlock(p);
- if (tasksize <= 0)
- continue;
- if (selected) {
- if (oom_score_adj < selected_oom_score_adj)
- continue;
- if (oom_score_adj == selected_oom_score_adj &&
- tasksize <= selected_tasksize)
- continue;
- }
- selected = p;
- selected_tasksize = tasksize;
- selected_oom_score_adj = oom_score_adj;
- lowmem_print(2, "select '%s' (%d), adj %hd, size %d, to kill\n",
- p->comm, p->pid, oom_score_adj, tasksize);
- }
- if (selected) {
- task_lock(selected);
- send_sig(SIGKILL, selected, 0);
- if (selected->mm)
- task_set_lmk_waiting(selected);
- task_unlock(selected);
- lowmem_print(1, "Killing '%s' (%d), adj %hd,\n"
- " to free %ldkB on behalf of '%s' (%d) because\n"
- " cache %ldkB is below limit %ldkB for oom_score_adj %hd\n"
- " Free memory is %ldkB above reserved\n",
- selected->comm, selected->pid,
- selected_oom_score_adj,
- selected_tasksize * (long)(PAGE_SIZE / 1024),
- current->comm, current->pid,
- other_file * (long)(PAGE_SIZE / 1024),
- minfree * (long)(PAGE_SIZE / 1024),
- min_score_adj,
- other_free * (long)(PAGE_SIZE / 1024));
- lowmem_deathpending_timeout = jiffies + HZ;
- rem += selected_tasksize;
- }
-
- lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
- sc->nr_to_scan, sc->gfp_mask, rem);
- rcu_read_unlock();
- return rem;
-}
-
-static struct shrinker lowmem_shrinker = {
- .scan_objects = lowmem_scan,
- .count_objects = lowmem_count,
- .seeks = DEFAULT_SEEKS * 16
-};
-
-static int __init lowmem_init(void)
-{
- register_shrinker(&lowmem_shrinker);
- return 0;
-}
-device_initcall(lowmem_init);
-
-/*
- * not really modular, but the easiest way to keep compat with existing
- * bootargs behaviour is to continue using module_param here.
- */
-module_param_named(cost, lowmem_shrinker.seeks, int, 0644);
-module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size, 0644);
-module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
- 0644);
-module_param_named(debug_level, lowmem_debug_level, uint, 0644);
-
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e93594b88130..3cc6c650fa6a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2347,7 +2347,6 @@ static inline void memalloc_noio_restore(unsigned int flags)
#define PFA_NO_NEW_PRIVS 0 /* May not gain new privileges. */
#define PFA_SPREAD_PAGE 1 /* Spread page cache over cpuset */
#define PFA_SPREAD_SLAB 2 /* Spread some slab caches over cpuset */
-#define PFA_LMK_WAITING 3 /* Lowmemorykiller is waiting */
#define TASK_PFA_TEST(name, func) \
@@ -2371,9 +2370,6 @@ TASK_PFA_TEST(SPREAD_SLAB, spread_slab)
TASK_PFA_SET(SPREAD_SLAB, spread_slab)
TASK_PFA_CLEAR(SPREAD_SLAB, spread_slab)
-TASK_PFA_TEST(LMK_WAITING, lmk_waiting)
-TASK_PFA_SET(LMK_WAITING, lmk_waiting)
-
/*
* task->jobctl flags
*/
--
2.11.0
--
Michal Hocko
SUSE Labs
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