[Qemu-devel] [PATCH] tap: minor code cleanup

[Qemu-devel] [PATCH] tap: minor code cleanup

[Michael S. Tsirkin]

remove a confusing comment.
TAP_DEFAULT_SNDBUF 0 is later translated to INT_MAX, so
let's set that value directly.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 net/tap-linux.c |    7 +------
 1 files changed, 1 insertions(+), 6 deletions(-)

diff --git a/net/tap-linux.c b/net/tap-linux.c
index 00f84d4..b8c0f3b 100644
--- a/net/tap-linux.c
+++ b/net/tap-linux.c
@@ -84,13 +84,8 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required
  * Unfortunately when it's enabled, and packets are sent
  * to other guests on the same host, the receiver
  * can lock up the transmitter indefinitely.
- *
- * To avoid packet loss, sndbuf should be set to a value lower than the tx
- * queue capacity of any destination network interface.
- * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
- * a good value, given a 1500 byte MTU.
  */
-#define TAP_DEFAULT_SNDBUF 0
+#define TAP_DEFAULT_SNDBUF INT_MAX
 
 int tap_set_sndbuf(int fd, QemuOpts *opts)
 {
-- 
1.7.3.2.91.g446ac

Re: [Qemu-devel] [PATCH] tap: minor code cleanup

[Markus Armbruster]

"Michael S. Tsirkin" <mst@redhat.com> writes:

> remove a confusing comment.
> TAP_DEFAULT_SNDBUF 0 is later translated to INT_MAX, so
> let's set that value directly.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  net/tap-linux.c |    7 +------
>  1 files changed, 1 insertions(+), 6 deletions(-)
>
> diff --git a/net/tap-linux.c b/net/tap-linux.c
> index 00f84d4..b8c0f3b 100644
> --- a/net/tap-linux.c
> +++ b/net/tap-linux.c
> @@ -84,13 +84,8 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required
>   * Unfortunately when it's enabled, and packets are sent
>   * to other guests on the same host, the receiver
>   * can lock up the transmitter indefinitely.
> - *
> - * To avoid packet loss, sndbuf should be set to a value lower than the tx
> - * queue capacity of any destination network interface.
> - * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
> - * a good value, given a 1500 byte MTU.
>   */
> -#define TAP_DEFAULT_SNDBUF 0
> +#define TAP_DEFAULT_SNDBUF INT_MAX
>  
>  int tap_set_sndbuf(int fd, QemuOpts *opts)
>  {

Can't comment on whether the comment should stay or go, but what about
tap_set_sndbuf()'s

    if (!sndbuf) {
        sndbuf = INT_MAX;
    }

Shouldn't that assign TAP_DEFAULT_SNDBUF now?