Green Tea cut my GC time 63%, and raised it 39%
One heap shape lost 63% of its collector CPU and gained 14% throughput. Another gained 39% collector CPU and lost nothing. Same flag, same binary pair, same machine.
#performance
Articles tagged “performance”
8 articlesRuntime internals
The GOGC I set next to GOMEMLIMIT never fired
GOGC=100 with a 256 MiB limit produced exactly what GOGC=off produced: same collections, same CPU share, same throughput. The tighter rule binds, the other goes quiet.
A 404 from net/http costs 62 allocations
A static route through net/http's mux costs 85.6 ns and nothing on the heap. A path that matches no pattern costs 2125.5 ns and 62 allocations.
benchstat reported p=0.000 between a function and itself
Two sub-benchmarks calling the same function with the same argument came back 1.10% apart at p=0.000. What a benchmark measures is not only your code.
GOMAXPROCS is not your thread count
GOMAXPROCS=1 with 200 goroutines blocked in read(2) produced 202 OS threads. Measured on go1.27.0, alongside the container case Go 1.25 changed.
sync.Pool survives one GC, not two
A pool holding 100 objects lost none across one collection and all 100 across two. Here is the victim cache, and what it costs at 122,000 ops per millisecond.
Escape analysis is not a rule of thumb
The compiler said "does not escape" and the benchmark reported 104 KiB per operation. Both were right. What -gcflags=-m actually tells you.
What the Go scheduler does when your goroutine blocks
A blocking syscall costs an OS thread. A blocking network read costs nothing. Measured with 200 goroutines, GOMAXPROCS=2 and a thread count.