* Pawel Moll <pawel.moll@xxxxxxx> wrote: > On Thu, 2014-09-18 at 15:34 +0100, Pawel Moll wrote: > > This patch adds a PERF_COUNT_SW_USERSPACE_EVENT type, > > which can be generated by user with PERF_EVENT_IOC_ENTRY > > ioctl command, which injects an event of said type into > > the perf buffer. > > It occurred to me last night that currently perf doesn't handle "write" > syscall at all, while this seems like the most natural way of > "injecting" userspace events into perf buffer. > > An ioctl would still be needed to set a type of the following events, > something like: > > ioctl(SET_TYPE, 0x42); > write(perf_fd, binaryblob, size); > ioctl(SET_TYPE, 0); > dprintf(perf_fd, "String"); > > which is fine for use cases when the type doesn't change often, > but would double the amount of syscalls when every single event > is of a different type. Perhaps there still should be a > "generating ioctl" taking both type and data/size in one go? Absolutely, there should be a single syscall. I'd even argue it should be a new prctl(): that way we could both generate user events for specific perf fds, but also into any currently active context (that allows just generation/injection of user events). In the latter case we might have no fd to work off from. And that is actually the really exciting usecase of your patches: we could generate user events via simple commands, and any external profiler/trace would be able to see them. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
