3cd8f9734d
The Go runtime has started to [lock down future uses of linkname][1] since
go1.23. In the go source code, containerd project has been marked in the
comment, [hall of shame][2]. Well, the go:linkname is used to fork no-op
subprocess efficiently. However, since that comment, I would like to use
ptrace and remove go:linkname in the whole repository.
With go1.22 `go:linkname`:
```bash
$ go test -bench=. -benchmem ./ -exec sudo
goos: linux
goarch: amd64
pkg: github.com/containerd/containerd/v2/core/mount
cpu: AMD Ryzen 7 5800H with Radeon Graphics
BenchmarkBatchRunGetUsernsFD_Concurrent1-16 2440 533320 ns/op 1145 B/op 43 allocs/op
BenchmarkBatchRunGetUsernsFD_Concurrent10-16 342 3661616 ns/op 11562 B/op 421 allocs/op
PASS
ok github.com/containerd/containerd/v2/core/mount 2.983s
```
With go1.22 `ptrace`:
```bash
$ go test -bench=. -benchmem ./ -exec sudo
goos: linux
goarch: amd64
pkg: github.com/containerd/containerd/v2/core/mount
cpu: AMD Ryzen 7 5800H with Radeon Graphics
BenchmarkBatchRunGetUsernsFD_Concurrent1-16 1785 739557 ns/op 3948 B/op 68 allocs/op
BenchmarkBatchRunGetUsernsFD_Concurrent10-16 328 4024300 ns/op 39601 B/op 671 allocs/op
PASS
ok github.com/containerd/containerd/v2/core/mount 3.104s
```
With go1.23 `ptrace`:
```bash
$ go test -bench=. -benchmem ./ -exec sudo
goos: linux
goarch: amd64
pkg: github.com/containerd/containerd/v2/core/mount
cpu: AMD Ryzen 7 5800H with Radeon Graphics
BenchmarkBatchRunGetUsernsFD_Concurrent1-16 1815 723252 ns/op 4220 B/op 69 allocs/op
BenchmarkBatchRunGetUsernsFD_Concurrent10-16 319 3957157 ns/op 42351 B/op 682 allocs/op
PASS
ok github.com/containerd/containerd/v2/core/mount 3.051s
```
Diff:
The `ptrace` is slower than `go:linkname` mode. However, it's accepctable.
```
goos: linux
goarch: amd64
pkg: github.com/containerd/containerd/v2/core/mount
cpu: AMD Ryzen 7 5800H with Radeon Graphics
│ go122-golinkname │ go122-ptrace │ go123-ptrace │
│ sec/op │ sec/op vs base │ sec/op vs base │
BatchRunGetUsernsFD_Concurrent1-16 533.3µ ± ∞ ¹ 739.6µ ± ∞ ¹ ~ (p=1.000 n=1) ² 723.3µ ± ∞ ¹ ~ (p=1.000 n=1) ²
BatchRunGetUsernsFD_Concurrent10-16 3.662m ± ∞ ¹ 4.024m ± ∞ ¹ ~ (p=1.000 n=1) ² 3.957m ± ∞ ¹ ~ (p=1.000 n=1) ²
geomean 1.397m 1.725m +23.45% 1.692m +21.06%
¹ need >= 6 samples for confidence interval at level 0.95
² need >= 4 samples to detect a difference at alpha level 0.05
│ go122-golinkname │ go122-ptrace │ go123-ptrace │
│ B/op │ B/op vs base │ B/op vs base │
BatchRunGetUsernsFD_Concurrent1-16 1.118Ki ± ∞ ¹ 3.855Ki ± ∞ ¹ ~ (p=1.000 n=1) ² 4.121Ki ± ∞ ¹ ~ (p=1.000 n=1) ²
BatchRunGetUsernsFD_Concurrent10-16 11.29Ki ± ∞ ¹ 38.67Ki ± ∞ ¹ ~ (p=1.000 n=1) ² 41.36Ki ± ∞ ¹ ~ (p=1.000 n=1) ²
geomean 3.553Ki 12.21Ki +243.65% 13.06Ki +267.43%
¹ need >= 6 samples for confidence interval at level 0.95
² need >= 4 samples to detect a difference at alpha level 0.05
│ go122-golinkname │ go122-ptrace │ go123-ptrace │
│ allocs/op │ allocs/op vs base │ allocs/op vs base │
BatchRunGetUsernsFD_Concurrent1-16 43.00 ± ∞ ¹ 68.00 ± ∞ ¹ ~ (p=1.000 n=1) ² 69.00 ± ∞ ¹ ~ (p=1.000 n=1) ²
BatchRunGetUsernsFD_Concurrent10-16 421.0 ± ∞ ¹ 671.0 ± ∞ ¹ ~ (p=1.000 n=1) ² 682.0 ± ∞ ¹ ~ (p=1.000 n=1) ²
geomean 134.5 213.6 +58.76% 216.9 +61.23%
¹ need >= 6 samples for confidence interval at level 0.95
² need >= 4 samples to detect a difference at alpha level 0.05
```
[1]: <https://github.com/golang/go/issues/67401>
[2]: <https://github.com/golang/go/blob/release-branch.go1.23/src/runtime/proc.go#L4820>
Signed-off-by: Wei Fu <fuweid89@gmail.com>
86 lines
2.3 KiB
Go
86 lines
2.3 KiB
Go
/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package sys
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import (
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"context"
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"errors"
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"fmt"
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"os"
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"sync"
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"github.com/containerd/log"
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"golang.org/x/sys/unix"
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)
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var (
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pidfdSupported bool
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pidfdSupportedOnce sync.Once
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)
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// SupportsPidFD returns true if current kernel supports pidfd.
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func SupportsPidFD() bool {
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pidfdSupportedOnce.Do(func() {
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logger := log.G(context.Background())
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if err := checkPidFD(); err != nil {
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logger.WithError(err).Error("failed to ensure the kernel supports pidfd")
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pidfdSupported = false
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return
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}
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pidfdSupported = true
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})
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return pidfdSupported
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}
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func checkPidFD() error {
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// Linux kernel supports pidfd_open(2) since v5.3.
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//
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// https://man7.org/linux/man-pages/man2/pidfd_open.2.html
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pidfd, err := unix.PidfdOpen(os.Getpid(), 0)
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if err != nil {
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return fmt.Errorf("failed to invoke pidfd_open: %w", err)
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}
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defer unix.Close(pidfd)
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// Linux kernel supports pidfd_send_signal(2) since v5.1.
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//
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// https://man7.org/linux/man-pages/man2/pidfd_send_signal.2.html
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if err := unix.PidfdSendSignal(pidfd, 0, nil, 0); err != nil {
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return fmt.Errorf("failed to invoke pidfd_send_signal: %w", err)
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}
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// The waitid(2) supports P_PIDFD since Linux kernel v5.4.
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//
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// https://man7.org/linux/man-pages/man2/waitid.2.html
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werr := IgnoringEINTR(func() error {
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return unix.Waitid(unix.P_PIDFD, pidfd, nil, unix.WEXITED, nil)
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})
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// The waitid returns ECHILD since current process isn't the child of current process.
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if !errors.Is(werr, unix.ECHILD) {
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return fmt.Errorf("failed to invoke waitid with P_PIDFD: wanted error %v, but got %v",
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unix.ECHILD, werr)
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}
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// NOTE: The CLONE_PIDFD flag has been supported since Linux kernel v5.2.
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// So assumption is that if waitid(2) supports P_PIDFD, current kernel
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// should support CLONE_PIDFD as well.
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return nil
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}
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