3 ms·
There is a option -smallframes that seems to be intended for conservative use cases. Below are the related configs and a test at what point they escape (+1).
by Yokohiii 11mo ago
There is a option -smallframes that seems to be intended for conservative use cases. Below are the related configs and a test at what point they escape (+1).
// -smallframes
// ir.MaxStackVarSize = 64 * 1024
// ir.MaxImplicitStackVarSize = 16 * 1024
a := [64 * 1024 +1]byte{}
b := make([]byte, 0, 16 * 1024 +1)
// default
// MaxStackVarSize = int64(128 * 1024)
// MaxImplicitStackVarSize = int64(64 * 1024)
c := [128 * 1024 +1]byte{}
d := make([]byte, 0, 64 * 1024 +1)
Not sure how to verify this, but the assumption you can allocate megabytes on the stack seems wrong. The output of the escape analysis for arrays is different then the make statement:
test/test.go:36:2: moved to heap: c
Maybe an overlook because it is a bit sneaky?
- masklinn 11mo ago> Not sure how to verify this, but the assumption you can allocate megabytes on the stack seems wrong. []byte{N: 0}
- deleted 11mo ago[deleted]
- Yokohiii 10mo agodoesn't make sense.
- masklinn 10mo agoAnd yet it does: https://godbolt.org/z/h9GW5v3YK https://godbolt.org/z/h9GW5v3YK And creates an on-stack slice whose size is only limited by Go's 1GB limit on individual stack frames: https://godbolt.org/z/rKzo8jre6 https://godbolt.org/z/rKzo8jre6 https://godbolt.org/z/don99e9cn https://godbolt.org/z/don99e9cn
- Yokohiii 10mo agoYea with more context it suddenly makes sense :p Interesting, [...] syntax works here as expected. So escape analysis simply doesn't look at the element list.