Subject: Re: [PATCH net-next 2/2] net: openvswitch: make masks cache size configurable

From: Florian Westphal <[email-masked]>
Date: Wed, 22 Jul 2020 21:22:52 +0200

Eelco Chaudron <[email-masked]> wrote:
> This patch makes the masks cache size configurable, or with
> a size of 0, disable it.
> 
> Reviewed-by: Paolo Abeni <[email-masked]>
> Signed-off-by: Eelco Chaudron <[email-masked]>
> ---
>  include/uapi/linux/openvswitch.h |    1 
>  net/openvswitch/datapath.c       |   11 +++++
>  net/openvswitch/flow_table.c     |   86 ++++++++++++++++++++++++++++++++++----
>  net/openvswitch/flow_table.h     |   10 ++++
>  4 files changed, 98 insertions(+), 10 deletions(-)
> 
> diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
> index 7cb76e5ca7cf..8300cc29dec8 100644
> --- a/include/uapi/linux/openvswitch.h
> +++ b/include/uapi/linux/openvswitch.h
> @@ -86,6 +86,7 @@ enum ovs_datapath_attr {
>  	OVS_DP_ATTR_MEGAFLOW_STATS,	/* struct ovs_dp_megaflow_stats */
>  	OVS_DP_ATTR_USER_FEATURES,	/* OVS_DP_F_*  */
>  	OVS_DP_ATTR_PAD,
> +	OVS_DP_ATTR_MASKS_CACHE_SIZE,

This new attr should probably get an entry in
datapath.c datapath_policy[].

> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
> @@ -1535,6 +1535,10 @@ static int ovs_dp_cmd_fill_info(struct datapath *dp, struct sk_buff *skb,
>  	if (nla_put_u32(skb, OVS_DP_ATTR_USER_FEATURES, dp->user_features))
>  		goto nla_put_failure;
>  
> +	if (nla_put_u32(skb, OVS_DP_ATTR_MASKS_CACHE_SIZE,
> +			ovs_flow_tbl_masks_cache_size(&dp->table)))
> +		goto nla_put_failure;
> +
>  	genlmsg_end(skb, ovs_header);
>  	return 0;

ovs_dp_cmd_msg_size() should add another nla_total_size(sizeof(u32))
to make sure there is enough space.

> +	if (a[OVS_DP_ATTR_MASKS_CACHE_SIZE]) {
> +		u32 cache_size;
> +
> +		cache_size = nla_get_u32(a[OVS_DP_ATTR_MASKS_CACHE_SIZE]);
> +		ovs_flow_tbl_masks_cache_resize(&dp->table, cache_size);
> +	}

I see a 0 cache size is legal (turns it off) and that the allocation
path has a few sanity checks as well.

Would it make sense to add min/max policy to datapath_policy[] for this
as well?