doujiang24 ef0dedce87 runtime/cgo: store M for C-created thread in pthread key ... In a C thread, it's necessary to acquire an extra M by using needm while invoking a Go function from C. But, needm and dropm are heavy costs due to the signal-related syscalls. So, we change to not dropm while returning back to C, which means binding the extra M to the C thread until it exits, to avoid needm and dropm on each C to Go call. Instead, we only dropm while the C thread exits, so the extra M won't leak. When invoking a Go function from C: Allocate a pthread variable using pthread_key_create, only once per shared object, and register a thread-exit-time destructor. And store the g0 of the current m into the thread-specified value of the pthread key, only once per C thread, so that the destructor will put the extra M back onto the extra M list while the C thread exits. When returning back to C: Skip dropm in cgocallback, when the pthread variable has been created, so that the extra M will be reused the next time invoke a Go function from C. This is purely a performance optimization. The old version, in which needm & dropm happen on each cgo call, is still correct too, and we have to keep the old version on systems with cgo but without pthreads, like Windows. This optimization is significant, and the specific value depends on the OS system and CPU, but in general, it can be considered as 10x faster, for a simple Go function call from a C thread. For the newly added BenchmarkCGoInCThread, some benchmark results: 1. it's 28x faster, from 3395 ns/op to 121 ns/op, in darwin OS & Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz 2. it's 6.5x faster, from 1495 ns/op to 230 ns/op, in Linux OS & Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz Fixes #51676 Change-Id: I380702fe2f9b6b401b2d6f04b0aba990f4b9ee6c GitHub-Last-Rev: 93dc64ad98 GitHub-Pull-Request: golang/go#51679 Reviewed-on: https://go-review.googlesource.com/c/go/+/392854 Reviewed-by: Ian Lance Taylor <iant@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Run-TryBot: thepudds <thepudds1460@gmail.com> Reviewed-by: Cherry Mui <cherryyz@google.com>		2023-03-24 16:00:24 +00:00
..
android	misc: use strings.Builder	2022-09-06 15:44:25 +00:00
arm
cgo	runtime/cgo: store M for C-created thread in pthread key	2023-03-24 16:00:24 +00:00
chrome/gophertool
ios
linkcheck
reboot	misc/reboot: overlay $GOROOT/lib in temporary goroot	2023-01-18 01:53:44 +00:00
swig
wasm	all: implement wasmimport directive	2023-03-02 05:28:55 +00:00
editors
go.mod	misc: update go.mod to 1.21	2023-01-26 16:55:59 +00:00