On 04/26/2016 03:26 AM, Zhou Jie wrote:
> net_init_tap has a huge stack usage of 8192 bytes approx.
> Moving large arrays to heap to reduce stack usage.
I am wondering. Why is 8k a problem for a user space program?
Please note that malloc/new like allocations are much more expensive
than stack allocation in terms of performance. This does not matter
here, but in your other patch that deals with the xmit function, I would
not be surprised if that actually harms performance.
Christian
>
> Signed-off-by: Zhou Jie <zhoujie2...@cn.fujitsu.com>
> ---
> net/tap.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/tap.c b/net/tap.c
> index 740e8a2..49817c7 100644
> --- a/net/tap.c
> +++ b/net/tap.c
> @@ -769,8 +769,8 @@ int net_init_tap(const NetClientOptions *opts, const char
> *name,
> return -1;
> }
> } else if (tap->has_fds) {
> - char *fds[MAX_TAP_QUEUES];
> - char *vhost_fds[MAX_TAP_QUEUES];
> + char **fds = g_new(char *, MAX_TAP_QUEUES);
> + char **vhost_fds = g_new(char *, MAX_TAP_QUEUES);
> int nfds, nvhosts;
>
> if (tap->has_ifname || tap->has_script || tap->has_downscript ||
> @@ -818,6 +818,8 @@ int net_init_tap(const NetClientOptions *opts, const char
> *name,
> return -1;
> }
> }
> + g_free(fds);
> + g_free(vhost_fds);
> } else if (tap->has_helper) {
> if (tap->has_ifname || tap->has_script || tap->has_downscript ||
> tap->has_vnet_hdr || tap->has_queues || tap->has_vhostfds) {
>
