netdev - Re: [PATCH net-next v1 1/1] net: openvswitch: ovs_packet_cmd_execute put sw

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Date:   Mon, 20 Feb 2023 15:11:17 +0800
From:   Eddy Tao <taoyuan_eddy@...mail.com>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     netdev@...r.kernel.org, Pravin B Shelar <pshelar@....org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, dev@...nvswitch.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v1 1/1] net: openvswitch: ovs_packet_cmd_execute
 put sw_flow mainbody in stack

Hi, Simon:


     About your concern for the stack size, it leads to more room for 
improvement.

I will file a new version which will have smaller stack occupation and 
better performance


The new revision is invoked by existing examples of using struct in 
stack, in the same file net/openvswitch/datapath.c

struct sw_flow_actions *get_flow_actions(..)
{
     struct sw_flow_key masked_key;==> sizeof sw_flow_key is 464 bytes

static noinline_for_stack int
ovs_nla_init_match_and_action(..)
{
     struct sw_flow_mask mask;==> sizeof sw_flow_mask is 496 bytes


The first example reminded me, revisiting the code in 
ovs_packet_cmd_execute, basically sw_flow serves as a container for 
sw_flow_actions and sw_flow_key only.

We do not need the bulk of tunnel info memory in sw_flow, which saves us 
200+ bytes further -- less is more.


The new revision will be presented shortly after some sanity and benchmark

eddy