go版本：1.13.4 在源碼sync/once.go中，以下注釋提到了“熱路徑”：type Once struct {    // done indicates whether the action has been performed.    // It is first in the struct because it is used in the hot path.    // The hot path is inlined at every call site.    // Placing done first allows more compact instructions on some architectures (amd64/x86),    // and fewer instructions (to calculate offset) on other architectures.    done uint32    m    Mutex}我的問(wèn)題是：這里的“熱路徑”是什么意思？“它位于結(jié)構(gòu)中的第一個(gè)”是否會(huì)使“熱路徑”訪問(wèn)更有效？為什么？