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[FLINK-39924] Fix jemalloc narenas configuration by using actual container CPU allowance #266

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[FLINK-39924] Fix jemalloc narenas configuration by using actual container CPU allowance #266

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51 changes: 51 additions & 0 deletions docker-entrypoint.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -120,6 +120,54 @@ process_flink_properties() {
fi
}

# FLINK-39924: jemalloc's default narenas = 4 * ncpus is taken from
# /proc/cpuinfo (host CPU count), ignoring the container's quota
# and idle arenas hold dirty pages until dirty_decay_ms, inflating
# RSS. Derive narenas from the cgroup CPU quota instead.
configure_jemalloc_narenas() {
case ",${MALLOC_CONF}," in
*,narenas:*)
echo "jemalloc: respecting user-supplied narenas in MALLOC_CONF=${MALLOC_CONF}"
return
;;
esac

local cpus="" cpu_quota cpu_period
if [ -r /sys/fs/cgroup/cpu.max ]; then
# cgroup v2
read -r cpu_quota cpu_period < /sys/fs/cgroup/cpu.max
if [ "$cpu_quota" != "max" ] && [ -n "$cpu_period" ] && [ "$cpu_period" -gt 0 ]; then
cpus=$(( (cpu_quota + cpu_period - 1) / cpu_period ))
fi
elif [ -r /sys/fs/cgroup/cpu/cpu.cfs_quota_us ] && [ -r /sys/fs/cgroup/cpu/cpu.cfs_period_us ]; then
# cgroup v1
cpu_quota=$(cat /sys/fs/cgroup/cpu/cpu.cfs_quota_us)
cpu_period=$(cat /sys/fs/cgroup/cpu/cpu.cfs_period_us)
if [ "$cpu_quota" -gt 0 ] && [ "$cpu_period" -gt 0 ]; then
cpus=$(( (cpu_quota + cpu_period - 1) / cpu_period ))
fi
fi
# Fall back to nproc when no quota is set (cpuset-pinned / unlimited).
if [ -z "$cpus" ] || [ "$cpus" -le 0 ]; then
cpus=$(nproc 2>/dev/null || echo 1)
fi

local narenas
if [ "$cpus" -le 1 ]; then
narenas=1
else
narenas=$(( cpus * 4 ))
fi

if [ -z "${MALLOC_CONF}" ]; then
export MALLOC_CONF="narenas:${narenas}"
echo "jemalloc: setting MALLOC_CONF=${MALLOC_CONF} (detected ${cpus} CPUs)"
else
export MALLOC_CONF="${MALLOC_CONF},narenas:${narenas}"
echo "jemalloc: appended narenas, MALLOC_CONF=${MALLOC_CONF} (detected ${cpus} CPUs)"
fi
}

maybe_enable_jemalloc() {
if [ "${DISABLE_JEMALLOC:-false}" == "false" ]; then
JEMALLOC_PATH="/usr/lib/$(uname -m)-linux-gnu/libjemalloc.so"
Expand All @@ -135,7 +183,10 @@ maybe_enable_jemalloc() {
MSG_PATH="$JEMALLOC_PATH and $JEMALLOC_FALLBACK"
fi
echo "WARNING: attempted to load jemalloc from $MSG_PATH but the library couldn't be found. glibc will be used instead."
return
fi

configure_jemalloc_narenas
fi
}

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