libprocessgroup: Look for memcg v2 MaxActivationDepth override (a890fa01) · Commits · e / os / android_system_core

init/Android.bp

+10 −0

Original line number	Diff line number	Diff line
		@@ -287,6 +287,9 @@ cc_binary {
		"make_f2fs",
		"mke2fs",
		"sload_f2fs",

		// TODO: Revert after go/android-memcgv2-exp b/386797433
		"memcgv2_activation_depth",
		],
		}

		@@ -685,3 +688,10 @@ phony {
		default: ["init_first_stage"],
		}),
		}

		// TODO: Revert after go/android-memcgv2-exp b/386797433
		sh_binary {
		name: "memcgv2_activation_depth",
		src: "memcgv2_activation_depth.sh",
		filename_from_src: true,
		}

init/memcgv2_activation_depth.sh

0 → 100644

+86 −0

Original line number	Diff line number	Diff line
		#!/bin/sh

		# This script adjusts overrides of the memcg v2 MaxActivationDepth value at runtime.
		# The override value needs to be accessible starting very early in the Android boot, where aconfig
		# flags and system properties do not work. A file on /metadata is used instead.

		# The kernel allows this to be as high as 65535, but our Android hierarchy is never that deep.
		MAX_ALLOWED_DEPTH=5

		# Store overridden MaxActivationDepths here for libprocessgroup to find them
		OVERRIDE_FILE_PATH="/metadata/libprocessgroup/memcg_v2_max_activation_depth"

		if [ "$#" -ne 1 ]
		then
		echo "Usage: $0 <memcg v2 MaxActivationDepth value>"
		exit 99
		fi

		max_activation_depth=$1

		if [[ $max_activation_depth != +([0-9]) ]]
		then
		echo "MaxActivationDepth value must be a positive integer: $max_activation_depth"
		exit 98
		fi

		if [ $max_activation_depth -lt 0 ]
		then
		echo "Negative MaxActivationDepth is invalid: $max_activation_depth"
		exit 97
		fi

		if [ $max_activation_depth -gt $MAX_ALLOWED_DEPTH ]
		then
		echo "MaxActivationDepth is too large: $max_activation_depth"
		exit 96
		fi

		grep memory /sys/fs/cgroup/cgroup.controllers
		if [ $? -ne 0 ]
		then
		echo "memcg v2 is not available on this device!"
		exit 95
		fi

		current_activation_depth=$(cat $OVERRIDE_FILE_PATH)
		if [ $? -ne 0 ]
		then
		# Find the default activation depth in the absence of any properties / overrides.
		#
		# To do this 100% correctly requires JSON parsing which we don't really want to do here.
		# We know that this will be called only for Pixel (for a limited-duration experiment), and that
		# Pixel does not override cgroups.json, therefore we can assume that the system cgroups.json has
		# only a single MaxActivationDepth entry which corresponds to the v2 memory controller. So we
		# can just grep for the default value.
		default_activation_depth=$(grep MaxActivationDepth /system/etc/cgroups.json \| tr -dc '0-9')
		if [ $? -ne 0 -o $default_activation_depth -gt $MAX_ALLOWED_DEPTH ]
		then
		# If MaxActivationDepth is not present, libprocessgroup does not limit how deep it will activate
		default_activation_depth=$MAX_ALLOWED_DEPTH
		fi
		current_activation_depth=$default_activation_depth
		fi

		# libprocessgroup will pick this up for all future cgroup creations, including on the next boot
		echo $max_activation_depth > $OVERRIDE_FILE_PATH

		if [ $max_activation_depth -lt $current_activation_depth ]
		then
		# We can deactivate memcgs which are deeper than the new depth value, however that would leave
		# behind zombie memcgs which would ruin the metrics produced from this device. The only way to
		# eliminate those zombies is to remove the entire cgroup, which we cannot do without killing
		# all the contained processes. So the only real option we have is to reboot here.
		# This should only happen once at the end of the experiment.
		echo "Rebooting due to decreased memcg v2 MaxActivationDepth"
		reboot
		elif [ $max_activation_depth -gt $current_activation_depth ]
		then
		for d in $(seq $max_activation_depth)
		do
		for f in $(find /sys/fs/cgroup/ -mindepth $d -maxdepth $d -name cgroup.subtree_control)
		do
		echo "+memory" > $f
		done
		done
		fi

libprocessgroup/util/util.cpp

+40 −1

Original line number	Diff line number	Diff line
		@@ -18,15 +18,19 @@

		#include <algorithm>
		#include <iterator>
		#include <mutex>
		#include <optional>
		#include <string_view>

		#include <mntent.h>
		#include <unistd.h>

		#include <android-base/file.h>
		#include <android-base/logging.h>
		#include <android-base/parseint.h>
		#include <android-base/properties.h>
		#include <android-base/stringprintf.h>
		#include <android-base/strings.h>
		#include <json/reader.h>
		#include <json/value.h>

		@@ -174,6 +178,38 @@ static std::optional<std::map<MountDir, MountOpts>> ReadCgroupV1Mounts() {
		return mounts;
		}

		// Keep the override file open to reduce open syscalls, but read it every time.
		// Note that memcgv2_activation_depth.sh can race with us here.
		std::optional<unsigned int> ReadMaxActivationDepthMetadataOverride() {
		static const char* OVERRIDE_FILE_PATH =
		"/metadata/libprocessgroup/memcg_v2_max_activation_depth";
		static int override_fd = open(OVERRIDE_FILE_PATH, O_RDONLY \| O_CLOEXEC);
		static std::mutex mtx;

		std::unique_lock lock(mtx);
		if (override_fd < 0) {
		override_fd = open(OVERRIDE_FILE_PATH, O_RDONLY \| O_CLOEXEC);
		if (override_fd < 0) return std::nullopt;
		}

		std::string depth_str;
		const bool ret = android::base::ReadFdToString(override_fd, &depth_str);
		lseek(override_fd, 0, SEEK_SET);
		lock.unlock();

		if (!ret) {
		PLOG(ERROR) << "Failed to read max activation depth override";
		return std::nullopt;
		}

		unsigned int depth;
		if (!android::base::ParseUint(android::base::Trim(depth_str), &depth)) {
		PLOG(ERROR) << "Failed to convert max activation depth override (" << depth_str << ')';
		return std::nullopt;
		}
		return depth;
		}

		} // anonymous namespace


		@@ -235,7 +271,10 @@ bool ReadDescriptors(CgroupDescriptorMap* descriptors) {
		bool ActivateControllers(const std::string& path, const CgroupDescriptorMap& descriptors) {
		for (const auto& [name, descriptor] : descriptors) {
		const uint32_t flags = descriptor.controller()->flags();
		const uint32_t max_activation_depth = descriptor.controller()->max_activation_depth();
		uint32_t max_activation_depth;
		std::optional<unsigned int> metadataMaxDepth = ReadMaxActivationDepthMetadataOverride();
		if (metadataMaxDepth) max_activation_depth = *metadataMaxDepth;
		else max_activation_depth = descriptor.controller()->max_activation_depth();
		const unsigned int depth = GetCgroupDepth(descriptor.controller()->path(), path);

		if (flags & CGROUPRC_CONTROLLER_FLAG_NEEDS_ACTIVATION && depth < max_activation_depth) {

rootdir/init.rc

+9 −0

Original line number	Diff line number	Diff line
		@@ -614,6 +614,9 @@ on post-fs

		mkdir /metadata/staged-install 0770 root system

		# TODO: Revert after go/android-memcgv2-exp b/386797433
		mkdir /metadata/libprocessgroup 0770 root system

		on late-fs
		# Ensure that tracefs has the correct permissions.
		# This does not work correctly if it is called in post-fs.
		@@ -1318,6 +1321,9 @@ on init && property:ro.debuggable=1
		# Multi-Gen LRU Experiment
		on property:persist.device_config.mglru_native.lru_gen_config=none
		write /sys/kernel/mm/lru_gen/enabled 0
		# Memcg v2 Experiment
		# TODO: Revert after go/android-memcgv2-exp b/386797433
		exec - system system -- /system/bin/memcgv2_activation_depth.sh 0
		on property:persist.device_config.mglru_native.lru_gen_config=core
		write /sys/kernel/mm/lru_gen/enabled 1
		on property:persist.device_config.mglru_native.lru_gen_config=core_and_mm_walk
		@@ -1326,6 +1332,9 @@ on property:persist.device_config.mglru_native.lru_gen_config=core_and_nonleaf_y
		write /sys/kernel/mm/lru_gen/enabled 5
		on property:persist.device_config.mglru_native.lru_gen_config=all
		write /sys/kernel/mm/lru_gen/enabled 7
		# Memcg v2 Experiment
		# TODO: Revert after go/android-memcgv2-exp b/386797433
		exec - system system -- /system/bin/memcgv2_activation_depth.sh 3

		# Allow other processes to run `snapshotctl` through `init`. This requires
		# `set_prop` permission on `snapshotctl_prop`.