chrubis@xxxxxxx writes: > Hi! >> > Looking carefully at the io_setup.2 man page it says: >> > >> > ... >> > The io_setup() system call creates an asynchronous I/O context capable >> > of concurrently processing at least nr_events. >> > ... >> > ^ >> > The 'at least' caught my eye, as it is it >> > may suggest that the nr_events is low limit >> > on the number of events. >> > >> > >> > Wouldn't be 'at most' more appropriate here? Quick look in the kernel >> > sources suggest that it allocates buffers for nr_events elements. >> > >> > Or am I missing something? >> >> When the kernel ring buffer is setup, it is created in page size >> chunks, and nr_events is rounded up: >> >> /* Compensate for the ring buffer's head/tail overlap entry */ >> nr_events += 2; /* 1 is required, 2 for good luck */ >> >> size = sizeof(struct aio_ring); >> size += sizeof(struct io_event) * nr_events; >> nr_pages = (size + PAGE_SIZE-1) >> PAGE_SHIFT; >> >> if (nr_pages < 0) >> return -EINVAL; >> >> nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring)) / sizeof(struct io_event); > > Ah, now it all makes sense. > > And I'm thinking if it is worth of adding more clear description. I don't think so, since it's an implementation detail and subject to change. Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
