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derp,types,util: use bufio Peek+Discard for allocation-free fast reads (#19067)

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Replace byte-at-a-time ReadByte loops with Peek+Discard in the DERP
read path. Peek returns a slice into bufio's internal buffer without
allocating, and Discard advances the read pointer without copying.

Introduce util/bufiox with a BufferedReader interface and ReadFull
helper that uses Peek+copy+Discard as an allocation-free alternative
to io.ReadFull.

  - derp.ReadFrameHeader: replace 5× ReadByte with Peek(5)+Discard(5),
    reading the frame type and length directly from the peeked slice.
    Remove now-unused readUint32 helper.

    name                  old ns/op  new ns/op  speedup
    ReadFrameHeader-8     24.2       12.4       ~2x
    (0 allocs/op in both)

  - key.NodePublic.ReadRawWithoutAllocating: replace 32× ReadByte with
    bufiox.ReadFull. Addresses the "Dear future" comment about switching
    away from byte-at-a-time reads once a non-escaping alternative exists.

    name                              old ns/op  new ns/op  speedup
    NodeReadRawWithoutAllocating-8    140        43.6       ~3.2x
    (0 allocs/op in both)

  - derpserver.handleFramePing: replace io.ReadFull with bufiox.ReadFull.

Updates tailscale/corp#38509

Signed-off-by: Mike O'Driscoll <mikeo@tailscale.com>
This commit is contained in:
Mike O'Driscoll
2026-03-24 10:52:20 -04:00
committed by GitHub
parent 1d0fde6fc2
commit 1403920367
17 changed files with 231 additions and 47 deletions
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cmd/tailscale/depaware.txt
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@@ -258,6 +258,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
tailscale.com/types/tkatype from tailscale.com/types/key+
tailscale.com/types/views from tailscale.com/tailcfg+
tailscale.com/util/backoff from tailscale.com/cmd/tailscale/cli
tailscale.com/util/bufiox from tailscale.com/types/key
tailscale.com/util/cibuild from tailscale.com/health+
tailscale.com/util/clientmetric from tailscale.com/net/netcheck+
tailscale.com/util/cloudenv from tailscale.com/net/dnscache+