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Currently, we use `pipe` for `wakeup_create`, which requires ***two***
file descriptors. Furthermore, given its complexity inside, `pipe` is a
bit heavyweight for just a simple event wait/notify mechanism.
`eventfd` would be a more suitable solution for this kind of scenario,
kernel also advocates for developers to use `eventfd` instead of `pipe`
in some simple use cases:
Applications can use an eventfd file descriptor instead of a pipe
(see pipe(2) in all cases where a pipe is used simply to signal
events. The kernel overhead of an eventfd file descriptor is much
lower than that of a pipe, and only one file descriptor is required
(versus the two required for a pipe).
This change adds the new backend of `eventfd` for `wakeup_create` and
uses it where available, eliminating the overhead of `pipe`. Also, it
optimizes the `wakeup_create` to eliminate the system calls that make
file descriptors non-blocking by moving the logic of setting
non-blocking flags on file descriptors to `socketpair.c` and using
`SOCK_NONBLOCK` for `socketpair(2)`, `EFD_NONBLOCK` for `eventfd(2)`.
Ref:
https://man7.org/linux/man-pages/man7/pipe.7.html
https://man7.org/linux/man-pages/man2/eventfd.2.html
https://man7.org/linux/man-pages/man2/socketpair.2.html
https://www.gnu.org/software/gnulib/manual/html_node/eventfd.html
Closes #13874
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| .. | ||
| Platforms | ||
| cmake_uninstall.cmake.in | ||
| CMakeConfigurableFile.in | ||
| curl-config.cmake.in | ||
| CurlSymbolHiding.cmake | ||
| CurlTests.c | ||
| FindBearSSL.cmake | ||
| FindBrotli.cmake | ||
| FindCARES.cmake | ||
| FindGSS.cmake | ||
| FindLibPSL.cmake | ||
| FindLibSSH2.cmake | ||
| FindMbedTLS.cmake | ||
| FindMSH3.cmake | ||
| FindNGHTTP2.cmake | ||
| FindNGHTTP3.cmake | ||
| FindNGTCP2.cmake | ||
| FindQUICHE.cmake | ||
| FindWolfSSL.cmake | ||
| FindZstd.cmake | ||
| Macros.cmake | ||
| OtherTests.cmake | ||
| PickyWarnings.cmake | ||
| Utilities.cmake | ||