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6b729795c3
Replace the process-global Server.mu lookup in the packet send hot path
with a global hashtriemap mirror of local clientSet entries. The
authoritative clients map remains guarded by Server.mu; clientsAtomic is
only a lock-free fast path for active local clients.
Misses, stale inactive client sets, duplicate accounting, and mesh
forwarding still fall back to lookupDestUncached. This avoids taking
Server.mu for the common local active-client send path, at the cost of
adding one global concurrent map that mirrors Server.clients for local
peers.
The benchmark uses four destination peers. The before run sets
TS_DEBUG_DERP_DISABLE_PEER_HASHTRIE=true to force the old mutex lookup
path; the after run uses the hashtrie fast path.
goos: linux
goarch: amd64
pkg: tailscale.com/derp/derpserver
cpu: Intel(R) Xeon(R) 6975P-C
│ before │ after │
│ sec/op │ sec/op vs base │
LookupDestHashTrie-16 176.050n ± 1% 1.904n ± 6% -98.92% (p=0.000 n=10)
│ before │ after │
│ B/op │ B/op vs base │
LookupDestHashTrie-16 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹
¹ all samples are equal
│ before │ after │
│ allocs/op │ allocs/op vs base │
LookupDestHashTrie-16 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=10) ¹
¹ all samples are equal
Updates #3560 (very indirectly, historically)
Updates #19713 (as an alternative to that PR)
Change-Id: Ifb72e5c9854ad00e938cd24c6ab9c27312f297e8
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
11 lines
300 B
JSON
11 lines
300 B
JSON
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