On Sun, Mar 06, 2022 at 10:27:29PM +0200, Nir Soffer wrote:
> 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);
As an example program, we should probably demonstrate checking whether
this function call failed (even though such failure is unlikely).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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