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Message-ID: <20231011034344.104398-4-npiggin@gmail.com> Date: Wed, 11 Oct 2023 13:43:40 +1000 From: Nicholas Piggin <npiggin@...il.com> To: netdev@...r.kernel.org Cc: Nicholas Piggin <npiggin@...il.com>, dev@...nvswitch.org, Pravin B Shelar <pshelar@....org>, Aaron Conole <aconole@...hat.com>, "Eelco Chaudron" <echaudro@...hat.com>, "Ilya Maximets" <imaximet@...hat.com>, "Flavio Leitner" <fbl@...hat.com>, Ilya Maximets <i.maximets@....org> Subject: [PATCH 3/7] openvswitch: reduce stack usage in do_execute_actions From: Ilya Maximets <i.maximets@....org> do_execute_actions() function can be called recursively multiple times while executing actions that require pipeline forking or recirculations. It may also be re-entered multiple times if the packet leaves openvswitch module and re-enters it through a different port. Currently, there is a 256-byte array allocated on stack in this function that is supposed to hold NSH header. Compilers tend to pre-allocate that space right at the beginning of the function: a88: 48 81 ec b0 01 00 00 sub $0x1b0,%rsp NSH is not a very common protocol, but the space is allocated on every recursive call or re-entry multiplying the wasted stack space. Move the stack allocation to push_nsh() function that is only used if NSH actions are actually present. push_nsh() is also a simple function without a possibility for re-entry, so the stack is returned right away. With this change the preallocated space is reduced by 256 B per call: b18: 48 81 ec b0 00 00 00 sub $0xb0,%rsp Signed-off-by: Ilya Maximets <i.maximets@....org> --- net/openvswitch/actions.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c index 7a66574672d3..be15ef693284 100644 --- a/net/openvswitch/actions.c +++ b/net/openvswitch/actions.c @@ -349,11 +349,18 @@ static int push_eth(struct sk_buff *skb, struct sw_flow_key *key, return 0; } -static int push_nsh(struct sk_buff *skb, struct sw_flow_key *key, - const struct nshhdr *nh) +static noinline_for_stack int push_nsh(struct sk_buff *skb, + struct sw_flow_key *key, + const struct nlattr *a) { + u8 buffer[NSH_HDR_MAX_LEN]; + struct nshhdr *nh = (struct nshhdr *)buffer; int err; + err = nsh_hdr_from_nlattr(a, nh, NSH_HDR_MAX_LEN); + if (err) + return err; + err = nsh_push(skb, nh); if (err) return err; @@ -1477,17 +1484,9 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb, err = pop_eth(skb, key); break; - case OVS_ACTION_ATTR_PUSH_NSH: { - u8 buffer[NSH_HDR_MAX_LEN]; - struct nshhdr *nh = (struct nshhdr *)buffer; - - err = nsh_hdr_from_nlattr(nla_data(a), nh, - NSH_HDR_MAX_LEN); - if (unlikely(err)) - break; - err = push_nsh(skb, key, nh); + case OVS_ACTION_ATTR_PUSH_NSH: + err = push_nsh(skb, key, nla_data(a)); break; - } case OVS_ACTION_ATTR_POP_NSH: err = pop_nsh(skb, key); -- 2.42.0
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