mirror of https://github.com/tytydraco/ktweak
Tyler Nijmeh
2 years ago
parent
ca8ee592bb
commit
7e21801599
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#!/usr/bin/env bash
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# Written by Draco (tytydraco @ GitHub)
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# The name of the current branch for logging purposes
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BRANCH="latency"
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# Maximum unsigned integer size in C
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UINT_MAX="4294967295"
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# Duration in nanoseconds of one scheduling period
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SCHED_PERIOD="$((1 * 1000 * 1000))"
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# How many tasks should we have at a maximum in one scheduling period
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SCHED_TASKS="10"
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write() {
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# Bail out if file does not exist
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[[ ! -f "$1" ]] && return 1
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# Make file writable in case it is not already
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chmod +w "$1" 2> /dev/null
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# Write the new value and bail if there's an error
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if ! echo "$2" > "$1" 2> /dev/null
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then
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echo "Failed: $1 → $2"
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return 1
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fi
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# Log the success
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echo "$1 → $2"
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}
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# Check for root permissions and bail if not granted
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if [[ "$(id -u)" -ne 0 ]]
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then
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echo "No root permissions. Exiting."
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exit 1
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fi
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# Detect if we are running on Android
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grep -q android /proc/cmdline && ANDROID=true
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# Log the date and time for records sake
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echo "Time of execution: $(date)"
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echo "Branch: $BRANCH"
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# Sync to data in the rare case a device crashes
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sync
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# Limit max perf event processing time to this much CPU usage
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write /proc/sys/kernel/perf_cpu_time_max_percent 3
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# Group tasks for less stutter but less throughput
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write /proc/sys/kernel/sched_autogroup_enabled 1
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# Execute child process before parent after fork
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write /proc/sys/kernel/sched_child_runs_first 1
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# Preliminary requirement for the following values
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write /proc/sys/kernel/sched_tunable_scaling 0
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# Reduce the maximum scheduling period for lower latency
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write /proc/sys/kernel/sched_latency_ns "$SCHED_PERIOD"
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# Schedule this ratio of tasks in the guarenteed sched period
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write /proc/sys/kernel/sched_min_granularity_ns "$((SCHED_PERIOD / SCHED_TASKS))"
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# Require preeptive tasks to surpass half of a sched period in vmruntime
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write /proc/sys/kernel/sched_wakeup_granularity_ns "$((SCHED_PERIOD / 2))"
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# Reduce the frequency of task migrations
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write /proc/sys/kernel/sched_migration_cost_ns 5000000
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# Always allow sched boosting on top-app tasks
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[[ "$ANDROID" == true ]] && write /proc/sys/kernel/sched_min_task_util_for_colocation 0
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# Improve real time latencies by reducing the scheduler migration time
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write /proc/sys/kernel/sched_nr_migrate 4
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# Disable scheduler statistics to reduce overhead
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write /proc/sys/kernel/sched_schedstats 0
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# Disable unnecessary printk logging
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write /proc/sys/kernel/printk_devkmsg off
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# Start non-blocking writeback later
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write /proc/sys/vm/dirty_background_ratio 3
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# Start blocking writeback later
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write /proc/sys/vm/dirty_ratio 30
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# Require dirty memory to stay in memory for longer
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write /proc/sys/vm/dirty_expire_centisecs 3000
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# Run the dirty memory flusher threads less often
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write /proc/sys/vm/dirty_writeback_centisecs 3000
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# Disable read-ahead for swap devices
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write /proc/sys/vm/page-cluster 0
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# Update /proc/stat less often to reduce jitter
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write /proc/sys/vm/stat_interval 10
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# Swap to the swap device at a fair rate
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write /proc/sys/vm/swappiness 100
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# Prioritize page cache over simple file structure nodes
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write /proc/sys/vm/vfs_cache_pressure 200
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# Enable Explicit Congestion Control
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write /proc/sys/net/ipv4/tcp_ecn 1
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# Enable fast socket open for receiver and sender
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write /proc/sys/net/ipv4/tcp_fastopen 3
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# Disable SYN cookies
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write /proc/sys/net/ipv4/tcp_syncookies 0
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if [[ -f "/sys/kernel/debug/sched_features" ]]
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then
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# Consider scheduling tasks that are eager to run
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write /sys/kernel/debug/sched_features NEXT_BUDDY
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# Some sources report large latency spikes during large migrations
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write /sys/kernel/debug/sched_features NO_TTWU_QUEUE
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fi
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[[ "$ANDROID" == true ]] && if [[ -d "/dev/stune/" ]]
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then
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# Prefer to schedule top-app tasks on idle CPUs
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write /dev/stune/top-app/schedtune.prefer_idle 1
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# Mark top-app as boosted, find high-performing CPUs
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write /dev/stune/top-app/schedtune.boost 1
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fi
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# Loop over each CPU in the system
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for cpu in /sys/devices/system/cpu/cpu*/cpufreq
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do
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# Fetch the available governors from the CPU
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avail_govs="$(cat "$cpu/scaling_available_governors")"
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# Attempt to set the governor in this order
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for governor in schedutil interactive
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do
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# Once a matching governor is found, set it and break for this CPU
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if [[ "$avail_govs" == *"$governor"* ]]
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then
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write "$cpu/scaling_governor" "$governor"
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break
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fi
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done
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done
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# Apply governor specific tunables for schedutil
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find /sys/devices/system/cpu/ -name schedutil -type d | while IFS= read -r governor
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do
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# Consider changing frequencies once per scheduling period
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write "$governor/up_rate_limit_us" 0
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write "$governor/down_rate_limit_us" 0
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write "$governor/rate_limit_us" 0
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# Jump to hispeed frequency at this load percentage
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write "$governor/hispeed_load" 85
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write "$governor/hispeed_freq" "$UINT_MAX"
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done
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# Apply governor specific tunables for interactive
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find /sys/devices/system/cpu/ -name interactive -type d | while IFS= read -r governor
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do
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# Consider changing frequencies once per scheduling period
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write "$governor/timer_rate" 0
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write "$governor/min_sample_time" 0
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# Jump to hispeed frequency at this load percentage
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write "$governor/go_hispeed_load" 85
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write "$governor/hispeed_freq" "$UINT_MAX"
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done
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for queue in /sys/block/*/queue
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do
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# Choose the first governor available
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avail_scheds="$(cat "$queue/scheduler")"
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for sched in cfq noop kyber bfq mq-deadline none
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do
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if [[ "$avail_scheds" == *"$sched"* ]]
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then
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write "$queue/scheduler" "$sched"
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break
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fi
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done
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# Do not use I/O as a source of randomness
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write "$queue/add_random" 0
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# Disable I/O statistics accounting
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write "$queue/iostats" 0
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# Reduce heuristic read-ahead in exchange for I/O latency
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write "$queue/read_ahead_kb" 32
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# Reduce the maximum number of I/O requests in exchange for latency
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write "$queue/nr_requests" 32
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done
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# Always return success, even if the last write fails
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exit 0
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