David Anderson 0909e90890 util/lru: replace container/list with a custom ring implementation ... pre-generics container/list is quite unpleasant to use, and the pointer manipulation operations for an LRU are simple enough to implement directly now that we have generic types. With this change, the LRU uses a ring (aka circularly linked list) rather than a simple doubly-linked list as its internals, because the ring makes list manipulation edge cases more regular: the only remaining edge case is the transition between 0 and 1 elements, rather than also having to deal specially with manipulating the first and last members of the list. While the primary purpose was improved readability of the code, as it turns out removing the indirection through an interface box also speeds up the LRU: │ before.txt │ after.txt │ │ sec/op │ sec/op vs base │ LRU-32 67.05n ± 2% 59.73n ± 2% -10.90% (p=0.000 n=20) │ before.txt │ after.txt │ │ B/op │ B/op vs base │ LRU-32 21.00 ± 0% 10.00 ± 0% -52.38% (p=0.000 n=20) │ before.txt │ after.txt │ │ allocs/op │ allocs/op vs base │ LRU-32 0.000 ± 0% 0.000 ± 0% ~ (p=1.000 n=20) ¹ Updates #cleanup Signed-off-by: David Anderson <danderson@tailscale.com>		2023-09-07 16:04:39 -07:00
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lru_test.go	util/lru: add a microbenchmark	2023-09-07 16:04:39 -07:00
lru.go	util/lru: replace container/list with a custom ring implementation	2023-09-07 16:04:39 -07:00