Re: [Libguestfs] [PATCH libnbd 2/3] examples: copy-libev: Do not initialize pread buffer

This safety feature is not needed since we handle pread errors, and even if we did not, we use initialized buffers. Testing shows 10% speedup when copying a real image.

+++ b/examples/copy-libev.c @@ -647,20 +647,26 @@ main (int argc, char *argv[]) size = nbd_get_size (src.nbd); if (size > nbd_get_size (dst.nbd)) FAIL ("Destinatio is not large enough\n"); /* Check destination server capabilities. */ dst.can_zero = nbd_can_zero (dst.nbd) > 0; + /* Disable pread buffer initialization. This is not needed since we + * handle pread errors, and even if we fail to handle errors, we use + * initialized buffers. */ + + nbd_set_pread_initialize (src.nbd, false);