libnetwork/resolvconf: some cleaning up and optimisations #44234
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thaJeztah
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tianon
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@corhere ptal 🤗 |
corhere
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| func hashData(data []byte) []byte { | ||
| f := sha256.Sum256(data) | ||
| out := make([]byte, 2*sha256.Size) | ||
| hex.Encode(out, f[:]) | ||
| return append([]byte("sha256:"), out...) | ||
| } |
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It can be done with even fewer allocs:
Suggested change
| func hashData(data []byte) []byte { | |
| f := sha256.Sum256(data) | |
| out := make([]byte, 2*sha256.Size) | |
| hex.Encode(out, f[:]) | |
| return append([]byte("sha256:"), out...) | |
| } | |
| const hashPrefix = "sha256:" | |
| func hashData(data []byte) []byte { | |
| out := make([]byte, len(hashPrefix)+hex.EncodedLen(sha256.Size)) | |
| copy(out, hashPrefix) | |
| f := sha256.Sum256(data) | |
| hex.Encode(out[len(hashPrefix):], f[:]) | |
| return out | |
| } |
The code seemed overly complicated, requiring a reader to be constructed,
where in all cases, the data was already available in a variable. This patch
simplifies the utility to not require a reader, which also makes it a bit
more performant:
go install golang.org/x/perf/cmd/benchstat@latest
GO111MODULE=off go test -run='^$' -bench=. -count=20 > old.txt
GO111MODULE=off go test -run='^$' -bench=. -count=20 > new.txt
benchstat old.txt new.txt
name old time/op new time/op delta
HashData-10 201ns ± 1% 128ns ± 1% -36.16% (p=0.000 n=18+20)
name old alloc/op new alloc/op delta
HashData-10 416B ± 0% 208B ± 0% -50.00% (p=0.000 n=20+20)
name old allocs/op new allocs/op delta
HashData-10 6.00 ± 0% 3.00 ± 0% -50.00% (p=0.000 n=20+20)
A small change was made in `Build()`, which previously returned the resolv.conf
data, even if the function failed to write it. In the new variation, `nil` is
consistently returned on failures.
Note that in various places, the hash is not even used, so we may be able to
simplify things more after this.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
After my last change, I noticed that the hash is used as a []byte in most
cases (other than tests). This patch updates the type to use a []byte, which
(although unlikely very important) also improves performance:
Compared to the previous version:
benchstat new.txt new2.txt
name old time/op new time/op delta
HashData-10 128ns ± 1% 116ns ± 1% -9.77% (p=0.000 n=20+20)
name old alloc/op new alloc/op delta
HashData-10 208B ± 0% 88B ± 0% -57.69% (p=0.000 n=20+20)
name old allocs/op new allocs/op delta
HashData-10 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.000 n=20+20)
And compared to the original version:
benchstat old.txt new2.txt
name old time/op new time/op delta
HashData-10 201ns ± 1% 116ns ± 1% -42.39% (p=0.000 n=18+20)
name old alloc/op new alloc/op delta
HashData-10 416B ± 0% 88B ± 0% -78.85% (p=0.000 n=20+20)
name old allocs/op new allocs/op delta
HashData-10 6.00 ± 0% 2.00 ± 0% -66.67% (p=0.000 n=20+20)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The test was assuming that the "source" file was always "/etc/resolv.conf", but the `Get()` function uses `Path()` to find the location of resolv.conf, which may be different. While at it, also changed some `t.Fatalf()` to `t.Errorf()`, and renamed some variables for clarity. Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Use t.TempDir() for convenience, and change some t.Fatal's to Errors, so that all tests can run instead of failing early. Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Looks like the intent is to exclude windows (which wouldn't have /etc/resolv.conf nor systemd), but most tests would run fine elsewhere. This allows running the tests on macOS for local testing. Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
- Verify the content to be equal, not "contains"; this output should be predictable. - Also verify the content returned by the function to match. Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
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Forgot about this one; did a rebase to get a fresh run of CI, and will merge when it completes (I might do a follow up with that last bit of optimisation from #44234 (comment)) |
thaJeztah
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Some Windows failures are unrelated (may be an issue with Docker Hub; there was a similar issue earlier today); |
|
confirmed that those failures are unrelated; see #45415. bringing this one in 👍 |
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