util/timedutil: add sync.Pools for *time.Timer and *timeutil.Timer #13466
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We're allocating these timers frequently in hot code-paths. This reduces channel allocation (i.e. time.Timer.C) from 3% of total allocations to 2%.
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Reviewed 3 of 3 files at r1. Comments from Reviewable |
andreimatei
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May 29, 2022
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complete! 1 of 0 LGTMs obtained
pkg/util/timeutil/timer.go line 105 at r1 (raw file):
if res { // Only place the timer back in the pool if we successfully stopped // it. Otherwise, we'd have to read from the channel if !t.Read.
and would it be bad to read from the channel? Shouldn't we do that and always place the timer in the pool?
nvanbenschoten
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Mar 5, 2024
This commit eliminates a case where a Timer's inner timer is not recycled. This was originally identified by @andreimatei in cockroachdb#13466 (review). ``` name old time/op new time/op delta Timer-10 152µs ± 1% 153µs ± 1% ~ (p=0.133 n=9+10) name old alloc/op new alloc/op delta Timer-10 200B ± 0% 0B -100.00% (p=0.000 n=10+10) name old allocs/op new allocs/op delta Timer-10 3.00 ± 0% 0.00 -100.00% (p=0.000 n=10+10) ``` Epic: None Release note: None
nvanbenschoten
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Mar 5, 2024
This commit eliminates a case where a Timer's inner timer is not recycled. This was originally identified by @andreimatei in cockroachdb#13466 (review). ``` name old time/op new time/op delta Timer-10 152µs ± 1% 153µs ± 1% ~ (p=0.133 n=9+10) name old alloc/op new alloc/op delta Timer-10 200B ± 0% 0B -100.00% (p=0.000 n=10+10) name old allocs/op new allocs/op delta Timer-10 3.00 ± 0% 0.00 -100.00% (p=0.000 n=10+10) ``` Epic: None Release note: None
craig bot
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Mar 6, 2024
119901: timeutil: stack-allocate Timer, remove pooling r=nvanbenschoten a=nvanbenschoten Informs #119593. Closes #38055. This PR removes the pooling of `timeutil.Timer` structs and, in doing so, permits the structs to be stack allocated so that no pooling is necessary. This superfluous (and in hindsight, harmful) memory pooling was introduced in f11ec1c, which also added very necessary pooling for the internal time.Timer structs. The pooling was harmful because it mandated a contract where Timer structs could not be used after their Stop method was called. This was surprising (time.Timer has no such limitation) and led to subtle use-after-free bugs over time (#61373 and #119595). It was also unnecessary because the outer Timer structs can be stack allocated. Ironically, the only thing that causes them to escape to the heap was the pooling mechanism itself. Removing pooling solves the issue. ``` name old time/op new time/op delta Timer-10 153µs ± 1% 152µs ± 1% ~ (p=0.589 n=10+9) name old alloc/op new alloc/op delta Timer-10 200B ± 0% 200B ± 0% ~ (all equal) name old allocs/op new allocs/op delta Timer-10 3.00 ± 0% 3.00 ± 0% ~ (all equal) ``` ---- The PR then improves the memory pooling of the inner `time.Timer` so that it is always recycled. This was originally identified by `@andreimatei` in #13466 (review). Doing so has a positive impact on the microbenchmark introduced in the first commit, demonstrating that timers can be stack-allocated and require zero heap allocations: ``` name old time/op new time/op delta Timer-10 152µs ± 1% 153µs ± 1% ~ (p=0.133 n=9+10) name old alloc/op new alloc/op delta Timer-10 200B ± 0% 0B -100.00% (p=0.000 n=10+10) name old allocs/op new allocs/op delta Timer-10 3.00 ± 0% 0.00 -100.00% (p=0.000 n=10+10) ``` ---- cc. `@andreimatei` `@ajwerner` Epic: None Release note: None Co-authored-by: Nathan VanBenschoten <[email protected]>
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We're allocating these timers frequently in hot code-paths. This reduces
channel allocation (i.e. time.Timer.C) from 3% of total allocations to
2%.
This change is