jlaitine opened a new pull request, #16194: URL: https://github.com/apache/nuttx/pull/16194
## Summary This enables mutex functionality in the nxsem code, enabling wait/post atomic fast paths, without needs for syscall, also when priority inheritance is enabled for mutexes. The basics of the implementations are as follows: - For mutexes, replace semaphore count with mutex holder, which consits of 1 bit for mutex internal locking and 31 bits for task PID - Instead of manipulating the count with atomic instructions, manipulate the mutex holder - Instead of allocating and storing the holder structure for the task's list for priority inheritance, do it at the time when task blocks on the mutex. Since there can be only one running holder for a mutex, this can be done. Doing this allows cleaning up the nxmutex interface to be a very thin wrapper on top of nxsem (e.g. removing the extra holder variable inside of nxmutex. Plain nxmutex could be just a typedeffed nxsem). This is left for future PRs. This also improves performance significantly in SMP and in CONFIG_BUILD_KERNEL / CONFIG_BUILD_PROTECTED targets, since most of the time there is no need for syscall to the kernel when a mutex is taken/posted. I am putting this as a draft for now and will do some more testing still on qemu targets ## Impact This has no functional impact. For the performance, on my real application the speed improvements on RISC-V are as follows in terms of CPU utilization: - RISCV 64bit (MFPS SMP, 4 harts, CONFIG_BUILD_KERNEL): CPU usage: 36 % -> 25 % - RISCV 64bit (MFPS SMP, 4 harts, CONFIG_BUILD_FLAT): CPU usage: 12% -> 9% ## Testing Real hardware: - Custom HW, mpfs (risc-v 64-bit): non-SMP and SMP 4 harts, both with CONFIG_BUILD_FLAT and CONFIG_BUILD_KERNEL. - Custom HW, i.MX93: Single core CONFIG_BUILD_FLAT and CONFIG_BUILD_KERNEL -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@nuttx.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
