1. __generic_file_aio_write – write data to a file<\/p>\n
\n ssize_t __generic_file_aio_write(struct kiocb * iocb, const struct iovec * iov, unsigned long nr_segs, loff_t * ppos);\n\niocb IO state structure (file, offset, etc.)\n\niov vector with data to write\n\nnr_segs number of segments in the vector\n\nppos position where to write\n\n\n<\/pre>\n2. Classroom<\/p>\n
\nAsynchronous I\/O, or non-blocking I\/O, is a form of input\/output\nprocessing that permits other processing to continue before the\ntransmission has finished. Input and output (I\/O) operations on a\ncomputer can be extremely slow compared to the processing of\ndata. An I\/O device can incorporate mechanical devices that must\nphysically move, such as a hard drive seeking a trackto read or\nwrite; this is often orders of magnitude slower than the switching\nof electric current. For example, during a disk operation that\ntakes ten milliseconds to perform, a processor that is clocked at\none gigahertz could have performed ten million\ninstruction-processing cycles. A simple approach to I\/O would be\nto start the access and then wait for it to complete. But such an\napproach (called synchronous I\/O or blocking I\/O) would block the\nprogress of a program while the communication is in progress,\nleaving system resources idle. When a program makes many I\/O\noperations, this means that the processor can spend almost all of\nits time idle waiting for I\/O operations to complete.\nAlternatively, it is possible, but more complicated to predict, to\nstart the communication and then perform processing that does not\nrequire that the I\/O has completed. This approach is called\nasynchronous input\/output. Any task that actually depends on the\nI\/O having completed (this includes both using the input values and\ncritical operations that claim to assure that a write operation has\nbeen completed) still needs to wait for the I\/O operation to\ncomplete, and thus is still blocked, but other processing that does\nnot have a dependency on the I\/O operation can continue.\n\nsource : http:\/\/en.wikipedia.org\/wiki\/Asynchronous_I\/O\n<\/pre>\n","protected":false},"excerpt":{"rendered":"1. __generic_file_aio_write – write data to a file ssize_t __generic_file_aio_write(struct kiocb * iocb, const struct iovec * iov, unsigned long nr_segs, loff_t * ppos); iocb IO state structure (file, offset, etc.) iov vector with data to write nr_segs number of segments in the vector ppos position where to write 2. Classroom Asynchronous I\/O, or non-blocking … <\/p>\n