Re: [PATCH v2] net:Add sysctl_tcp_sg_max_skb_frags

From: Eric Dumazet
Date: Wed Jan 27 2016 - 10:15:17 EST

On Wed, 2016-01-27 at 14:20 +0100, Hans Westgaard Ry wrote:
> Devices may have limits on the number of fragments in an skb they support.
> Current codebase uses a constant as maximum for number of fragments one
> skb can hold and use.
> When enabling scatter/gather and running traffic with many small messages
> the codebase uses the maximum number of fragments and may thereby violate
> the max for certain devices.
> The patch introduces a global variable as max number of fragments in
> scatter/gather.

Principle looks good, but we have to ask if other skb providers [1] will
add other sysctl, or if we could share a common one ?

If it is a common one, it should be /proc/sys/net/core/... instead
of /proc/sys/net/ipv4/tcp_....

Other providers include :

1) GRO stack
2) callers of sock_alloc_send_pskb(), alloc_skb_with_frags(),
sock_alloc_send_skb() ..

Thanks !