[feature] Inherit resource limits from cgroups (#1336)

When GTS is running in a container runtime which has configured CPU or
memory limits or under an init system that uses cgroups to impose CPU
and memory limits the values the Go runtime sees for GOMAXPROCS and
GOMEMLIMIT are still based on the host resources, not the cgroup.

At least for the throttling middlewares which use GOMAXPROCS to
configure their queue size, this can result in GTS running with values
too big compared to the resources that will actuall be available to it.

This introduces 2 dependencies which can pick up resource contraints
from the current cgroup and tune the Go runtime accordingly. This should
result in the different queues being appropriately sized and in general
more predictable performance. These dependencies are a no-op on
non-Linux systems or if running in a cgroup that doesn't set a limit on
CPU or memory.

The automatic tuning of GOMEMLIMIT can be disabled by either explicitly
setting GOMEMLIMIT yourself or by setting AUTOMEMLIMIT=off. The
automatic tuning of GOMAXPROCS can similarly be counteracted by setting
GOMAXPROCS yourself.

1 files changed, 116 insertions, 0 deletions

diff --git a/vendor/github.com/containerd/cgroups/subsystem.go b/vendor/github.com/containerd/cgroups/subsystem.go
new file mode 100644
index 000000000..b2f41854d
--- /dev/null
+++ b/vendor/github.com/containerd/cgroups/subsystem.go
@@ -0,0 +1,116 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package cgroups
+
+import (
+	"fmt"
+	"os"
+
+	v1 "github.com/containerd/cgroups/stats/v1"
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+)
+
+// Name is a typed name for a cgroup subsystem
+type Name string
+
+const (
+	Devices   Name = "devices"
+	Hugetlb   Name = "hugetlb"
+	Freezer   Name = "freezer"
+	Pids      Name = "pids"
+	NetCLS    Name = "net_cls"
+	NetPrio   Name = "net_prio"
+	PerfEvent Name = "perf_event"
+	Cpuset    Name = "cpuset"
+	Cpu       Name = "cpu"
+	Cpuacct   Name = "cpuacct"
+	Memory    Name = "memory"
+	Blkio     Name = "blkio"
+	Rdma      Name = "rdma"
+)
+
+// Subsystems returns a complete list of the default cgroups
+// available on most linux systems
+func Subsystems() []Name {
+	n := []Name{
+		Freezer,
+		Pids,
+		NetCLS,
+		NetPrio,
+		PerfEvent,
+		Cpuset,
+		Cpu,
+		Cpuacct,
+		Memory,
+		Blkio,
+		Rdma,
+	}
+	if !RunningInUserNS() {
+		n = append(n, Devices)
+	}
+	if _, err := os.Stat("/sys/kernel/mm/hugepages"); err == nil {
+		n = append(n, Hugetlb)
+	}
+	return n
+}
+
+type Subsystem interface {
+	Name() Name
+}
+
+type pather interface {
+	Subsystem
+	Path(path string) string
+}
+
+type creator interface {
+	Subsystem
+	Create(path string, resources *specs.LinuxResources) error
+}
+
+type deleter interface {
+	Subsystem
+	Delete(path string) error
+}
+
+type stater interface {
+	Subsystem
+	Stat(path string, stats *v1.Metrics) error
+}
+
+type updater interface {
+	Subsystem
+	Update(path string, resources *specs.LinuxResources) error
+}
+
+// SingleSubsystem returns a single cgroup subsystem within the base Hierarchy
+func SingleSubsystem(baseHierarchy Hierarchy, subsystem Name) Hierarchy {
+	return func() ([]Subsystem, error) {
+		subsystems, err := baseHierarchy()
+		if err != nil {
+			return nil, err
+		}
+		for _, s := range subsystems {
+			if s.Name() == subsystem {
+				return []Subsystem{
+					s,
+				}, nil
+			}
+		}
+		return nil, fmt.Errorf("unable to find subsystem %s", subsystem)
+	}
+}