util/pool: add package for storing and using a pool of items #12091

andrew-d · 2024-05-10T18:28:59Z

This can be used to implement a persistent pool (i.e. one that isn't cleared like sync.Pool is) of items–e.g. database connections.

Some benchmarks vs. a naive implementation that uses a single map iteration show a pretty meaningful improvement:

$ benchstat -col /impl ./bench.txt
goos: darwin
goarch: arm64
pkg: tailscale.com/util/pool
                   │    Pool     │                   map                    │
                   │   sec/op    │     sec/op      vs base                  │
Pool_AddDelete-10    10.56n ± 2%     15.11n ±  1%    +42.97% (p=0.000 n=10)
Pool_TakeRandom-10   56.75n ± 4%   1899.50n ± 20%  +3246.84% (p=0.000 n=10)
geomean              24.49n          169.4n         +591.74%

Updates https://github.com/tailscale/corp/issues/19900

Change-Id: Ie509cb65573c4726cfc3da9a97093e61c216ca18

andrew-d · 2024-05-10T18:30:10Z

@bradfitz you may recognize the shape of this as being inspired by your change in database/sql

util/pool/pool.go

bradfitz · 2024-05-24T17:38:07Z

util/pool/pool.go

+	// index is the current location of this item in pool.s. It gets set to
+	// -1 when the item is removed from the pool.
+	index *int


why -1 if it's a pointer? does niling it out not work? but -1 is fine.

We copy the pointer to a Handle, so having an underlying pointer makes it easy to detect (in Peek/etc.) whether an item has been removed just given the Handle

util/pool/pool.go

This can be used to implement a persistent pool (i.e. one that isn't cleared like sync.Pool is) of items–e.g. database connections. Some benchmarks vs. a naive implementation that uses a single map iteration show a pretty meaningful improvement: $ benchstat -col /impl ./bench.txt goos: darwin goarch: arm64 pkg: tailscale.com/util/pool │ Pool │ map │ │ sec/op │ sec/op vs base │ Pool_AddDelete-10 10.56n ± 2% 15.11n ± 1% +42.97% (p=0.000 n=10) Pool_TakeRandom-10 56.75n ± 4% 1899.50n ± 20% +3246.84% (p=0.000 n=10) geomean 24.49n 169.4n +591.74% Updates tailscale/corp#19900 Signed-off-by: Andrew Dunham <andrew@du.nham.ca> Change-Id: Ie509cb65573c4726cfc3da9a97093e61c216ca18

andrew-d requested review from bradfitz and maisem May 10, 2024 18:28

andrew-d force-pushed the andrew/util-pool branch 2 times, most recently from 2606285 to a33c6b8 Compare May 13, 2024 15:16

maisem reviewed May 24, 2024

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