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I am testing kernel asynchronous io functions (not posix aio) and am trying to figure out how it works. The code below is a complete program where I simply write an array repeatedly to a file opened using O_DIRECT. I get an error in the callback function "write missed bytes expect 1024 got 0" (see the fprintf statement in work_done()). For those not familiar with kernel aio, the code below does the following: Init some structs Prepare aio (io_prep_pwrite) Submit io requests (io_submit) Check for event completion (io_getevents) Call a callback function to see if everything went ok. I get an error at step 5. If I do not open the file using O_DIRECT, things work fine, but it beats the purpose of having async writes. Can someone tell me what I am doing wrong? Is this the correct usage of kernel aio, for example, is my use of callbacks correct? Are there any restrictions on the usage of O_DIRECT? I compile using 'gcc -Wall test.c -laio' Thanks in advance. /* * File: myaiocp.c * Author: kmehta * * Created on July 11, 2011, 12:50 PM * * * Testing kernel aio. * Program creates a 2D matrix and writes it multiple times to create a file of desired size. * Writes are performed using kernel aio functions (io_prep_pwrite, io_submit, etc.) */ #define _GNU_SOURCE #define _XOPEN_SOURCE 600 #include <stdio.h> #include <stdlib.h> #include <getopt.h> #include <pthread.h> #include <fcntl.h> #include <string.h> #include <sys/uio.h> #include <sys/time.h> #include <omp.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <errno.h> #include <libaio.h> char ** buf; long seg_size; int seg_rows; double total_size; char * filename; static int wait_count = 0; void io_task(); void cleanup(); void allocate_2D_matrix(int[]); int file_open(char *); void wr_done(io_conte

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