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Subject[RFC v2] Add mempressure cgroup
The main changes for the mempressure cgroup:

- Added documentation, describes APIs and the purpose;

- Implemented shrinker interface, this is based on Andrew's idea and
supersedes my "balance" level idea;

- The shrinker interface comes with a stress-test utility, that is what
Andrew was also asking for. A simple app that we can run and see if the
thing works as expected;

- Added reclaimer's target_mem_cgroup handling;

- As promised, added support for multiple listeners, and fixed some other
comments on the previous RFC.

Just for the reference, the first mempressure RFC:

http://lkml.org/lkml/2012/11/28/109

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
Documentation/cgroups/mempressure.txt | 89 ++++++
Documentation/cgroups/mempressure_test.c | 209 +++++++++++++
include/linux/cgroup_subsys.h | 6 +
include/linux/vmstat.h | 11 +
init/Kconfig | 12 +
mm/Makefile | 1 +
mm/mempressure.c | 488 +++++++++++++++++++++++++++++++
mm/vmscan.c | 4 +
8 files changed, 820 insertions(+)
create mode 100644 Documentation/cgroups/mempressure.txt
create mode 100644 Documentation/cgroups/mempressure_test.c
create mode 100644 mm/mempressure.c
diff --git a/Documentation/cgroups/mempressure.txt b/Documentation/cgroups/mempressure.txt
new file mode 100644
index 0000000..913accc
--- /dev/null
+++ b/Documentation/cgroups/mempressure.txt
@@ -0,0 +1,89 @@
+ Memory pressure cgroup
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+ Before using the mempressure cgroup, make sure you have it mounted:
+
+ # cd /sys/fs/cgroup/
+ # mkdir mempressure
+ # mount -t cgroup cgroup ./mempressure -o mempressure
+
+ After that, you can use the following files:
+
+ /sys/fs/cgroup/.../mempressure.shrinker
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ The file implements userland shrinker (memory reclaimer) interface, so
+ that the kernel can ask userland to help with the memory reclaiming
+ process.
+
+ There are two basic concepts: chunks and chunks' size. The program must
+ tell the kernel the granularity of its allocations (chunk size) and the
+ number of reclaimable chunks. The granularity may be not 100% accurate,
+ but the more it is accurate, the better. I.e. suppose the application
+ has 200 page renders cached (but not displayed), 1MB each. So the chunk
+ size is 1MB, and the number of chunks is 200.
+
+ The granularity is specified during shrinker registration (i.e. via
+ argument to the event_control cgroup file; and it is OK to register
+ multiple shrinkers for different granularities). The number of
+ reclaimable chunks is specified by writing to the mempressure.shrinker
+ file.
+
+ The notification comes through the eventfd() interface. Upon the
+ notification, a read() from the eventfd returns the number of chunks to
+ reclaim (free).
+
+ It is assumed that the application will free the specified amount of
+ chunks before reading from the eventfd again. If that is not the case,
+ suppose the program was not able to reclaim the chunks, then application
+ should re-add the amount of chunks by writing to the
+ mempressure.shrinker file (otherwise the chunks won't be accounted by
+ the kernel, since it assumes that they were reclaimed).
+
+ Event control:
+ Used to setup shrinker events. There is only one argument for the
+ event control: chunk size in bytes.
+ Read:
+ Not implemented.
+ Write:
+ Writes must be in "<eventfd> <number of chunks>" format. Positive
+ numbers increment the internal counter, negative numbers decrement it
+ (but the kernel prevents the counter from falling down below zero).
+ Test:
+ See mempressure_test.c
+
+ /sys/fs/cgroup/.../mempressure.level
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ Instead of working on the bytes level (like shrinkers), one may decide
+ to maintain the interactivity/memory allocation cost.
+
+ For this, the cgroup has memory pressure level notifications, and the
+ levels are defined like this:
+
+ The "low" level means that the system is reclaiming memory for new
+ allocations. Monitoring reclaiming activity might be useful for
+ maintaining overall system's cache level. Upon notification, the program
+ (typically "Activity Manager") might analyze vmstat and act in advance
+ (i.e. prematurely shutdown unimportant services).
+
+ The "medium" level means that the system is experiencing medium memory
+ pressure, there is some mild swapping activity. Upon this event
+ applications may decide to free any resources that can be easily
+ reconstructed or re-read from a disk. Note that for a fine-grained
+ control, you should probably use the shrinker interface, as described
+ above.
+
+ The "oom" level means that the system is actively thrashing, it is about
+ to out of memory (OOM) or even the in-kernel OOM killer is on its way to
+ trigger. Applications should do whatever they can to help the system.
+
+ Event control:
+ Is used to setup an eventfd with a level threshold. The argument to
+ the event control specifies the level threshold.
+ Read:
+ Reads mempory presure levels: low, medium or oom.
+ Write:
+ Not implemented.
+ Test:
+ To set up a notification:
+
+ # cgroup_event_listener ./mempressure.level low
+ ("low", "medium", "oom" are permitted.)
diff --git a/Documentation/cgroups/mempressure_test.c b/Documentation/cgroups/mempressure_test.c
new file mode 100644
index 0000000..9747fd6
--- /dev/null
+++ b/Documentation/cgroups/mempressure_test.c
@@ -0,0 +1,209 @@
+/*
+ * mempressure shrinker test
+ *
+ * Copyright 2012 Linaro Ltd.
+ * Anton Vorontsov <anton.vorontsov@linaro.org>
+ *
+ * It is pretty simple: we create two threads, the first one constantly
+ * tries to allocate memory (more than we physically have), the second
+ * thread listens to the kernel shrinker notifications and frees asked
+ * amount of chunks. When we allocate more than available RAM, the two
+ * threads start to fight. Idially, we should not OOM (but if we reclaim
+ * slower than we allocate, things might OOM). Also, ideally we should not
+ * grow swap too much.
+ *
+ * The test accepts no arguments, so you can just run it and observe the
+ * output and memory usage (e.g. 'watch -n 0.2 free -m'). Upon ctrl+c, the
+ * test prints total amount of bytes we helped to reclaim.
+ *
+ * Compile with -pthread.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <signal.h>
+#include <errno.h>
+#include <sys/eventfd.h>
+#include <sys/sysinfo.h>
+
+#define CG "/sys/fs/cgroup/mempressure"
+#define CG_EVENT_CONTROL (CG "/cgroup.event_control")
+#define CG_SHRINKER (CG "/mempressure.shrinker")
+
+#define CHUNK_SIZE (1 * 1024 * 1024)
+
+static size_t num_chunks;
+
+static void **chunks;
+static pthread_mutex_t *locks;
+static int efd;
+static int sfd;
+
+static inline void pabort(bool f, int code, const char *str)
+{
+ if (!f)
+ return;
+ perror(str);
+ printf("(%d)\n", code);
+ abort();
+}
+
+static void init_shrinker(void)
+{
+ int cfd;
+ int ret;
+ char *str;
+
+ cfd = open(CG_EVENT_CONTROL, O_WRONLY);
+ pabort(cfd < 0, cfd, CG_EVENT_CONTROL);
+
+ sfd = open(CG_SHRINKER, O_RDWR);
+ pabort(sfd < 0, sfd, CG_SHRINKER);
+
+ efd = eventfd(0, 0);
+ pabort(efd < 0, efd, "eventfd()");
+
+ ret = asprintf(&str, "%d %d %d\n", efd, sfd, CHUNK_SIZE);
+ printf("%s\n", str);
+ pabort(ret == -1, ret, "control string");
+
+ ret = write(cfd, str, ret + 1);
+ pabort(ret == -1, ret, "write() to event_control");
+}
+
+static void add_reclaimable(int chunks)
+{
+ int ret;
+ char *str;
+
+ ret = asprintf(&str, "%d %d\n", efd, CHUNK_SIZE);
+ pabort(ret == -1, ret, "add_reclaimable, asprintf");
+
+ ret = write(sfd, str, ret + 1);
+ pabort(ret <= 0, ret, "add_reclaimable, write");
+}
+
+static int chunks_to_reclaim(void)
+{
+ uint64_t n = 0;
+ int ret;
+
+ ret = read(efd, &n, sizeof(n));
+ pabort(ret <= 0, ret, "read() from eventfd");
+
+ printf("%d chunks to reclaim\n", (int)n);
+
+ return n;
+}
+
+static unsigned int reclaimed;
+
+static void print_stats(int signum)
+{
+ printf("\nTOTAL: helped to reclaim %d chunks (%d MB)\n",
+ reclaimed, reclaimed * CHUNK_SIZE / 1024 / 1024);
+ exit(0);
+}
+
+static void *shrinker_thr_fn(void *arg)
+{
+ puts("shrinker thread started");
+
+ sigaction(SIGINT, &(struct sigaction){.sa_handler = print_stats}, NULL);
+
+ while (1) {
+ unsigned int i = 0;
+ int n;
+
+ n = chunks_to_reclaim();
+
+ reclaimed += n;
+
+ while (n) {
+ pthread_mutex_lock(&locks[i]);
+ if (chunks[i]) {
+ free(chunks[i]);
+ chunks[i] = NULL;
+ n--;
+ }
+ pthread_mutex_unlock(&locks[i]);
+
+ i = (i + 1) % num_chunks;
+ }
+ }
+ return NULL;
+}
+
+static void consume_memory(void)
+{
+ unsigned int i = 0;
+ unsigned int j = 0;
+
+ puts("consuming memory...");
+
+ while (1) {
+ pthread_mutex_lock(&locks[i]);
+ if (!chunks[i]) {
+ chunks[i] = malloc(CHUNK_SIZE);
+ pabort(!chunks[i], 0, "chunks alloc failed");
+ memset(chunks[i], 0, CHUNK_SIZE);
+ j++;
+ }
+ pthread_mutex_unlock(&locks[i]);
+
+ if (j >= num_chunks / 10) {
+ add_reclaimable(num_chunks / 10);
+ printf("added %d reclaimable chunks\n", j);
+ j = 0;
+ }
+
+ i = (i + 1) % num_chunks;
+ }
+}
+
+int main(int argc, char *argv[])
+{
+ int ret;
+ int i;
+ pthread_t shrinker_thr;
+ struct sysinfo si;
+
+ ret = sysinfo(&si);
+ pabort(ret != 0, ret, "sysinfo()");
+
+ num_chunks = (si.totalram + si.totalswap) * si.mem_unit / 1024 / 1024;
+
+ chunks = malloc(sizeof(*chunks) * num_chunks);
+ locks = malloc(sizeof(*locks) * num_chunks);
+ pabort(!chunks || !locks, ENOMEM, NULL);
+
+ init_shrinker();
+
+ for (i = 0; i < num_chunks; i++) {
+ ret = pthread_mutex_init(&locks[i], NULL);
+ pabort(ret != 0, ret, "pthread_mutex_init");
+ }
+
+ ret = pthread_create(&shrinker_thr, NULL, shrinker_thr_fn, NULL);
+ pabort(ret != 0, ret, "pthread_create(shrinker)");
+
+ consume_memory();
+
+ ret = pthread_join(shrinker_thr, NULL);
+ pabort(ret != 0, ret, "pthread_join(shrinker)");
+
+ return 0;
+}
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index f204a7a..b9802e2 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -37,6 +37,12 @@ SUBSYS(mem_cgroup)

/* */

+#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_MEMPRESSURE)
+SUBSYS(mpc_cgroup)
+#endif
+
+/* */
+
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_DEVICE)
SUBSYS(devices)
#endif
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 92a86b2..3f7f7d2 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -10,6 +10,17 @@

extern int sysctl_stat_interval;

+struct mem_cgroup;
+#ifdef CONFIG_CGROUP_MEMPRESSURE
+extern void vmpressure(struct mem_cgroup *memcg,
+ ulong scanned, ulong reclaimed);
+extern void vmpressure_prio(struct mem_cgroup *memcg, int prio);
+#else
+static inline void vmpressure(struct mem_cgroup *memcg,
+ ulong scanned, ulong reclaimed) {}
+static inline void vmpressure_prio(struct mem_cgroup *memcg, int prio) {}
+#endif
+
#ifdef CONFIG_VM_EVENT_COUNTERS
/*
* Light weight per cpu counter implementation.
diff --git a/init/Kconfig b/init/Kconfig
index 6fdd6e3..5c308be 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -826,6 +826,18 @@ config MEMCG_KMEM
the kmem extension can use it to guarantee that no group of processes
will ever exhaust kernel resources alone.

+config CGROUP_MEMPRESSURE
+ bool "Memory pressure monitor for Control Groups"
+ help
+ The memory pressure monitor cgroup provides a facility for
+ userland programs so that they could easily assist the kernel
+ with the memory management. This includes simple memory pressure
+ notifications and a full-fledged userland reclaimer.
+
+ For more information see Documentation/cgroups/mempressure.txt
+
+ If unsure, say N.
+
config CGROUP_HUGETLB
bool "HugeTLB Resource Controller for Control Groups"
depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
diff --git a/mm/Makefile b/mm/Makefile
index 6b025f8..40cee19 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_MIGRATION) += migrate.o
obj-$(CONFIG_QUICKLIST) += quicklist.o
obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o
obj-$(CONFIG_MEMCG) += memcontrol.o page_cgroup.o
+obj-$(CONFIG_CGROUP_MEMPRESSURE) += mempressure.o
obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o
obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o
diff --git a/mm/mempressure.c b/mm/mempressure.c
new file mode 100644
index 0000000..e39a33d
--- /dev/null
+++ b/mm/mempressure.c
@@ -0,0 +1,488 @@
+/*
+ * Linux VM pressure
+ *
+ * Copyright 2012 Linaro Ltd.
+ * Anton Vorontsov <anton.vorontsov@linaro.org>
+ *
+ * Based on ideas from Andrew Morton, David Rientjes, KOSAKI Motohiro,
+ * Leonid Moiseichuk, Mel Gorman, Minchan Kim and Pekka Enberg.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ */
+
+#include <linux/cgroup.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/vmstat.h>
+#include <linux/eventfd.h>
+#include <linux/swap.h>
+#include <linux/printk.h>
+
+static void mpc_vmpressure(struct mem_cgroup *memcg, ulong s, ulong r);
+
+/*
+ * Generic VM Pressure routines (no cgroups or any other API details)
+ */
+
+/*
+ * The window size is the number of scanned pages before we try to analyze
+ * the scanned/reclaimed ratio (or difference).
+ *
+ * It is used as a rate-limit tunable for the "low" level notification,
+ * and for averaging medium/oom levels. Using small window sizes can cause
+ * lot of false positives, but too big window size will delay the
+ * notifications.
+ *
+ * The same window size also used for the shrinker, so be aware. It might
+ * be a good idea to derive the window size from the machine size, similar
+ * to what we do for the vmstat.
+ */
+static const uint vmpressure_win = SWAP_CLUSTER_MAX * 16;
+static const uint vmpressure_level_med = 60;
+static const uint vmpressure_level_oom = 99;
+static const uint vmpressure_level_oom_prio = 4;
+
+enum vmpressure_levels {
+ VMPRESSURE_LOW = 0,
+ VMPRESSURE_MEDIUM,
+ VMPRESSURE_OOM,
+ VMPRESSURE_NUM_LEVELS,
+};
+
+static const char *vmpressure_str_levels[] = {
+ [VMPRESSURE_LOW] = "low",
+ [VMPRESSURE_MEDIUM] = "medium",
+ [VMPRESSURE_OOM] = "oom",
+};
+
+static enum vmpressure_levels vmpressure_level(uint pressure)
+{
+ if (pressure >= vmpressure_level_oom)
+ return VMPRESSURE_OOM;
+ else if (pressure >= vmpressure_level_med)
+ return VMPRESSURE_MEDIUM;
+ return VMPRESSURE_LOW;
+}
+
+static ulong vmpressure_calc_level(uint win, uint s, uint r)
+{
+ ulong p;
+
+ if (!s)
+ return 0;
+
+ /*
+ * We calculate the ratio (in percents) of how many pages were
+ * scanned vs. reclaimed in a given time frame (window). Note that
+ * time is in VM reclaimer's "ticks", i.e. number of pages
+ * scanned. This makes it possible to set desired reaction time
+ * and serves as a ratelimit.
+ */
+ p = win - (r * win / s);
+ p = p * 100 / win;
+
+ pr_debug("%s: %3lu (s: %6u r: %6u)\n", __func__, p, s, r);
+
+ return vmpressure_level(p);
+}
+
+void vmpressure(struct mem_cgroup *memcg, ulong scanned, ulong reclaimed)
+{
+ if (!scanned)
+ return;
+ mpc_vmpressure(memcg, scanned, reclaimed);
+}
+
+void vmpressure_prio(struct mem_cgroup *memcg, int prio)
+{
+ if (prio > vmpressure_level_oom_prio)
+ return;
+
+ /* OK, the prio is below the threshold, send the pre-OOM event. */
+ vmpressure(memcg, vmpressure_win, 0);
+}
+
+/*
+ * Memory pressure cgroup code
+ */
+
+struct mpc_event {
+ struct eventfd_ctx *efd;
+ enum vmpressure_levels level;
+ struct list_head node;
+};
+
+struct mpc_shrinker {
+ struct eventfd_ctx *efd;
+ size_t chunks;
+ size_t chunk_sz;
+ struct list_head node;
+};
+
+struct mpc_state {
+ struct cgroup_subsys_state css;
+
+ uint scanned;
+ uint reclaimed;
+ struct mutex sr_lock;
+
+ struct list_head events;
+ struct mutex events_lock;
+
+ struct list_head shrinkers;
+ struct mutex shrinkers_lock;
+
+ struct work_struct work;
+};
+
+static struct mpc_state *wk2mpc(struct work_struct *wk)
+{
+ return container_of(wk, struct mpc_state, work);
+}
+
+static struct mpc_state *css2mpc(struct cgroup_subsys_state *css)
+{
+ return container_of(css, struct mpc_state, css);
+}
+
+static struct mpc_state *tsk2mpc(struct task_struct *tsk)
+{
+ return css2mpc(task_subsys_state(tsk, mpc_cgroup_subsys_id));
+}
+
+static struct mpc_state *cg2mpc(struct cgroup *cg)
+{
+ return css2mpc(cgroup_subsys_state(cg, mpc_cgroup_subsys_id));
+}
+
+static void mpc_shrinker(struct mpc_state *mpc, ulong s, ulong r)
+{
+ struct mpc_shrinker *sh;
+ ssize_t to_reclaim_pages = s - r;
+
+ if (!to_reclaim_pages)
+ return;
+
+ mutex_lock(&mpc->shrinkers_lock);
+
+ /*
+ * To make accounting more precise and to avoid excessive
+ * communication with the kernel, we operate on chunks instead of
+ * bytes. Say, asking to free 8 KBs makes little sense if
+ * granularity of allocations is 10 MBs. Also, knowing the
+ * granularity (chunk size) and the number of reclaimable chunks,
+ * we just ask that N chunks should be freed, and we assume that
+ * it will be freed, thus we decrement our internal counter
+ * straight away (i.e. userland does not need to respond how much
+ * was reclaimed). But, if userland could not free it, it is
+ * responsible to increment the counter back.
+ */
+ list_for_each_entry(sh, &mpc->shrinkers, node) {
+ size_t to_reclaim_chunks;
+
+ if (!sh->chunks)
+ continue;
+
+ to_reclaim_chunks = to_reclaim_pages *
+ PAGE_SIZE / sh->chunk_sz;
+ to_reclaim_chunks = min(sh->chunks, to_reclaim_chunks);
+
+ if (!to_reclaim_chunks)
+ continue;
+
+ sh->chunks -= to_reclaim_chunks;
+
+ eventfd_signal(sh->efd, to_reclaim_chunks);
+
+ to_reclaim_pages -= to_reclaim_chunks *
+ sh->chunk_sz / PAGE_SIZE;
+ if (to_reclaim_pages <= 0)
+ break;
+ }
+
+ mutex_unlock(&mpc->shrinkers_lock);
+}
+
+static void mpc_event(struct mpc_state *mpc, ulong s, ulong r)
+{
+ struct mpc_event *ev;
+ int level = vmpressure_calc_level(vmpressure_win, s, r);
+
+ mutex_lock(&mpc->events_lock);
+
+ list_for_each_entry(ev, &mpc->events, node) {
+ if (level >= ev->level)
+ eventfd_signal(ev->efd, 1);
+ }
+
+ mutex_unlock(&mpc->events_lock);
+}
+
+static void mpc_vmpressure_wk_fn(struct work_struct *wk)
+{
+ struct mpc_state *mpc = wk2mpc(wk);
+ ulong s;
+ ulong r;
+
+ mutex_lock(&mpc->sr_lock);
+ s = mpc->scanned;
+ r = mpc->reclaimed;
+ mpc->scanned = 0;
+ mpc->reclaimed = 0;
+ mutex_unlock(&mpc->sr_lock);
+
+ mpc_shrinker(mpc, s, r);
+ mpc_event(mpc, s, r);
+}
+
+static void __mpc_vmpressure(struct mpc_state *mpc, ulong s, ulong r)
+{
+ mutex_lock(&mpc->sr_lock);
+ mpc->scanned += s;
+ mpc->reclaimed += r;
+ mutex_unlock(&mpc->sr_lock);
+
+ if (s < vmpressure_win || work_pending(&mpc->work))
+ return;
+
+ schedule_work(&mpc->work);
+}
+
+static void mpc_vmpressure(struct mem_cgroup *memcg, ulong s, ulong r)
+{
+ /*
+ * There are two options for implementing cgroup pressure
+ * notifications:
+ *
+ * - Store pressure counter atomically in the task struct. Upon
+ * hitting 'window' wake up a workqueue that will walk every
+ * task and sum per-thread pressure into cgroup pressure (to
+ * which the task belongs). The cons are obvious: bloats task
+ * struct, have to walk all processes and makes pressue less
+ * accurate (the window becomes per-thread);
+ *
+ * - Store pressure counters in per-cgroup state. This is easy and
+ * straightforward, and that's how we do things here. But this
+ * requires us to not put the vmpressure hooks into hotpath,
+ * since we have to grab some locks.
+ */
+
+#ifdef CONFIG_MEMCG
+ if (memcg) {
+ struct cgroup_subsys_state *css = mem_cgroup_css(memcg);
+ struct cgroup *cg = css->cgroup;
+ struct mpc_state *mpc = cg2mpc(cg);
+
+ if (mpc)
+ __mpc_vmpressure(mpc, s, r);
+ return;
+ }
+#endif
+ task_lock(current);
+ __mpc_vmpressure(tsk2mpc(current), s, r);
+ task_unlock(current);
+}
+
+static struct cgroup_subsys_state *mpc_create(struct cgroup *cg)
+{
+ struct mpc_state *mpc;
+
+ mpc = kzalloc(sizeof(*mpc), GFP_KERNEL);
+ if (!mpc)
+ return ERR_PTR(-ENOMEM);
+
+ mutex_init(&mpc->sr_lock);
+ mutex_init(&mpc->events_lock);
+ mutex_init(&mpc->shrinkers_lock);
+ INIT_LIST_HEAD(&mpc->events);
+ INIT_LIST_HEAD(&mpc->shrinkers);
+ INIT_WORK(&mpc->work, mpc_vmpressure_wk_fn);
+
+ return &mpc->css;
+}
+
+static void mpc_destroy(struct cgroup *cg)
+{
+ struct mpc_state *mpc = cg2mpc(cg);
+
+ kfree(mpc);
+}
+
+static ssize_t mpc_read_level(struct cgroup *cg, struct cftype *cft,
+ struct file *file, char __user *buf,
+ size_t sz, loff_t *ppos)
+{
+ struct mpc_state *mpc = cg2mpc(cg);
+ uint level;
+ const char *str;
+
+ mutex_lock(&mpc->sr_lock);
+
+ level = vmpressure_calc_level(vmpressure_win,
+ mpc->scanned, mpc->reclaimed);
+
+ mutex_unlock(&mpc->sr_lock);
+
+ str = vmpressure_str_levels[level];
+ return simple_read_from_buffer(buf, sz, ppos, str, strlen(str));
+}
+
+static int mpc_register_level_event(struct cgroup *cg, struct cftype *cft,
+ struct eventfd_ctx *eventfd,
+ const char *args)
+{
+ struct mpc_state *mpc = cg2mpc(cg);
+ struct mpc_event *ev;
+ int lvl;
+
+ for (lvl = 0; lvl < VMPRESSURE_NUM_LEVELS; lvl++) {
+ if (!strcmp(vmpressure_str_levels[lvl], args))
+ break;
+ }
+
+ if (lvl >= VMPRESSURE_NUM_LEVELS)
+ return -EINVAL;
+
+ ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+ if (!ev)
+ return -ENOMEM;
+
+ ev->efd = eventfd;
+ ev->level = lvl;
+
+ mutex_lock(&mpc->events_lock);
+ list_add(&ev->node, &mpc->events);
+ mutex_unlock(&mpc->events_lock);
+
+ return 0;
+}
+
+static void mpc_unregister_event(struct cgroup *cg, struct cftype *cft,
+ struct eventfd_ctx *eventfd)
+{
+ struct mpc_state *mpc = cg2mpc(cg);
+ struct mpc_event *ev;
+
+ mutex_lock(&mpc->events_lock);
+ list_for_each_entry(ev, &mpc->events, node) {
+ if (ev->efd != eventfd)
+ continue;
+ list_del(&ev->node);
+ kfree(ev);
+ break;
+ }
+ mutex_unlock(&mpc->events_lock);
+}
+
+static int mpc_register_shrinker(struct cgroup *cg, struct cftype *cft,
+ struct eventfd_ctx *eventfd,
+ const char *args)
+{
+ struct mpc_state *mpc = cg2mpc(cg);
+ struct mpc_shrinker *sh;
+ ulong chunk_sz;
+ int ret;
+
+ ret = kstrtoul(args, 10, &chunk_sz);
+ if (ret)
+ return ret;
+
+ sh = kzalloc(sizeof(*sh), GFP_KERNEL);
+ if (!sh)
+ return -ENOMEM;
+
+ sh->efd = eventfd;
+ sh->chunk_sz = chunk_sz;
+
+ mutex_lock(&mpc->shrinkers_lock);
+ list_add(&sh->node, &mpc->shrinkers);
+ mutex_unlock(&mpc->shrinkers_lock);
+
+ return 0;
+}
+
+static void mpc_unregister_shrinker(struct cgroup *cg, struct cftype *cft,
+ struct eventfd_ctx *eventfd)
+{
+ struct mpc_state *mpc = cg2mpc(cg);
+ struct mpc_shrinker *sh;
+
+ mutex_lock(&mpc->shrinkers_lock);
+ list_for_each_entry(sh, &mpc->shrinkers, node) {
+ if (sh->efd != eventfd)
+ continue;
+ list_del(&sh->node);
+ kfree(sh);
+ break;
+ }
+ mutex_unlock(&mpc->shrinkers_lock);
+}
+
+static int mpc_write_shrinker(struct cgroup *cg, struct cftype *cft,
+ const char *str)
+{
+ struct mpc_state *mpc = cg2mpc(cg);
+ struct mpc_shrinker *sh;
+ struct eventfd_ctx *eventfd;
+ struct file *file;
+ ssize_t chunks;
+ int fd;
+ int ret;
+
+ ret = sscanf(str, "%d %zd\n", &fd, &chunks);
+ if (ret != 2)
+ return -EINVAL;
+
+ file = fget(fd);
+ if (!file)
+ return -EBADF;
+
+ eventfd = eventfd_ctx_fileget(file);
+
+ mutex_lock(&mpc->shrinkers_lock);
+
+ /* Can avoid the loop once we introduce ->priv for eventfd_ctx. */
+ list_for_each_entry(sh, &mpc->shrinkers, node) {
+ if (sh->efd != eventfd)
+ continue;
+ if (chunks < 0 && abs(chunks) > sh->chunks)
+ sh->chunks = 0;
+ else
+ sh->chunks += chunks;
+ break;
+ }
+
+ mutex_unlock(&mpc->shrinkers_lock);
+
+ eventfd_ctx_put(eventfd);
+ fput(file);
+
+ return 0;
+}
+
+static struct cftype mpc_files[] = {
+ {
+ .name = "level",
+ .read = mpc_read_level,
+ .register_event = mpc_register_level_event,
+ .unregister_event = mpc_unregister_event,
+ },
+ {
+ .name = "shrinker",
+ .register_event = mpc_register_shrinker,
+ .unregister_event = mpc_unregister_shrinker,
+ .write_string = mpc_write_shrinker,
+ },
+ {},
+};
+
+struct cgroup_subsys mpc_cgroup_subsys = {
+ .name = "mempressure",
+ .subsys_id = mpc_cgroup_subsys_id,
+ .create = mpc_create,
+ .destroy = mpc_destroy,
+ .base_cftypes = mpc_files,
+};
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 48550c6..d8ff846 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1877,6 +1877,9 @@ restart:
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
sc, LRU_ACTIVE_ANON);

+ vmpressure(sc->target_mem_cgroup,
+ sc->nr_scanned - nr_scanned, nr_reclaimed);
+
/* reclaim/compaction might need reclaim to continue */
if (should_continue_reclaim(lruvec, nr_reclaimed,
sc->nr_scanned - nr_scanned, sc))
@@ -2099,6 +2102,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
count_vm_event(ALLOCSTALL);

do {
+ vmpressure_prio(sc->target_mem_cgroup, sc->priority);
sc->nr_scanned = 0;
aborted_reclaim = shrink_zones(zonelist, sc);

--
1.8.0

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