ref: c1d40df49550393f3afe53fb6e6d500dfa8eb7a8
dir: /sys/src/cmd/aux/seek.c/
#include <u.h> #include <libc.h> void main(int argc, char **argv) { char buf[512]; vlong size; vlong pos; vlong ns; int fd; int i; if(argc != 2) { fprint(2, "usage: %s /dev/sd??/data\n", argv[0]); exits("usage"); } srand(time(0)); fd = open(argv[1], OREAD); if(fd < 0) sysfatal("open: %r"); size = seek(fd, 0, 2) / 512; ns = nsec(); for(i=0;i<100;i++) { pos = (vlong)(frand() * size); if(pread(fd, buf, 512, 512 * pos) < 512) sysfatal("read: %r"); } ns = nsec() - ns; print("%.3g\n", ((double)ns)/100000000); exits(nil); }