diff mbox series

[ovs-dev,v4] ofproto-dpif-xlate: Reduce stack usage in recursive xlate functions

Message ID 20230609140134.640641-1-mkp@redhat.com
State Superseded
Headers show
Series [ovs-dev,v4] ofproto-dpif-xlate: Reduce stack usage in recursive xlate functions | expand

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Commit Message

Mike Pattrick June 9, 2023, 2:01 p.m. UTC
Several xlate actions used in recursive translation currently store a
large amount of information on the stack. This can result in handler
threads quickly running out of stack space despite before
xlate_resubmit_resource_check() is able to terminate translation. This
patch reduces stack usage by over 3kb from several translation actions.

This patch also moves some trace function from do_xlate_actions into its
own function to reduce stack usage.

Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=2104779
Signed-off-by: Mike Pattrick <mkp@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>

---
Since v1:
 - Refactored code into specialized functions and renamed variables for
 improved readability.
Since v2:
 - Removed inline keywords
Since v3:
 - Improved formatting.
---
 ofproto/ofproto-dpif-xlate.c | 214 ++++++++++++++++++++++-------------
 1 file changed, 138 insertions(+), 76 deletions(-)

Comments

Mike Pattrick June 9, 2023, 2:50 p.m. UTC | #1
On Fri, Jun 9, 2023 at 10:01 AM Mike Pattrick <mkp@redhat.com> wrote:
>
> Several xlate actions used in recursive translation currently store a
> large amount of information on the stack. This can result in handler
> threads quickly running out of stack space despite before
> xlate_resubmit_resource_check() is able to terminate translation. This
> patch reduces stack usage by over 3kb from several translation actions.
>
> This patch also moves some trace function from do_xlate_actions into its
> own function to reduce stack usage.
>
> Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=2104779
> Signed-off-by: Mike Pattrick <mkp@redhat.com>
> Reviewed-by: Simon Horman <simon.horman@corigine.com>
>
> ---
> Since v1:
>  - Refactored code into specialized functions and renamed variables for
>  improved readability.
> Since v2:
>  - Removed inline keywords
> Since v3:
>  - Improved formatting.

Disregard this revision, I sent out the wrong file by mistake.

Thank you,
M
diff mbox series

Patch

diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
index 29f4daa63..2c45831d1 100644
--- a/ofproto/ofproto-dpif-xlate.c
+++ b/ofproto/ofproto-dpif-xlate.c
@@ -501,6 +501,85 @@  ctx_cancel_freeze(struct xlate_ctx *ctx)
 
 static void finish_freezing(struct xlate_ctx *ctx);
 
+/* These functions and structure are used to save stack space in actions that
+ * need to retain a large amount of xlate_ctx state. */
+struct xretained_state {
+    union mf_subvalue new_stack[1024 / sizeof(union mf_subvalue)];
+    uint64_t actset_stub[1024 / 8];
+    struct ofpbuf old_stack;
+    struct ofpbuf old_action_set;
+    struct flow old_flow;
+    struct flow old_base;
+    struct flow_tnl flow_tnl_mask;
+};
+
+/* The return of this function must be freed by xretain_state_restore(). */
+static struct xretained_state *
+xretain_state_save(struct xlate_ctx *ctx)
+{
+    struct xretained_state *retained = xmalloc(sizeof *retained);
+
+    retained->old_flow = ctx->xin->flow;
+    retained->old_stack = ctx->stack;
+    retained->old_action_set = ctx->action_set;
+    ofpbuf_use_stub(&ctx->stack, retained->new_stack,
+                    sizeof retained->new_stack);
+    ofpbuf_use_stub(&ctx->action_set, retained->actset_stub,
+                sizeof retained->actset_stub);
+
+    return retained;
+}
+
+static void
+xretain_tunnel_mask_save(struct xlate_ctx *ctx,
+                         struct xretained_state *retained,
+                         const struct xport *out_dev)
+{
+    struct flow *flow = &ctx->xin->flow;
+
+    retained->flow_tnl_mask = ctx->wc->masks.tunnel;
+}
+
+static void
+xretain_base_flow_save(const struct xlate_ctx *ctx,
+                       struct xretained_state *retained)
+{
+    retained->old_base = ctx->base_flow;
+}
+
+static void
+xretain_base_flow_restore(struct xlate_ctx *ctx,
+                          const struct xretained_state *retained)
+{
+    ctx->base_flow = retained->old_base;
+}
+
+static void
+xretain_flow_restore(struct xlate_ctx *ctx,
+                     const struct xretained_state *retained)
+{
+    ctx->xin->flow = retained->old_flow;
+}
+
+static void
+xretain_tunnel_mask_restore(struct xlate_ctx *ctx,
+                            const struct xretained_state *retained)
+{
+    ctx->wc->masks.tunnel = retained->flow_tnl_mask;
+}
+
+static void
+xretain_state_restore(struct xlate_ctx *ctx, struct xretained_state *retained)
+{
+    ctx->xin->flow = retained->old_flow;
+    ofpbuf_uninit(&ctx->action_set);
+    ctx->action_set = retained->old_action_set;
+    ofpbuf_uninit(&ctx->stack);
+    ctx->stack = retained->old_stack;
+
+    free(retained);
+}
+
 /* A controller may use OFPP_NONE as the ingress port to indicate that
  * it did not arrive on a "real" port.  'ofpp_none_bundle' exists for
  * when an input bundle is needed for validation (e.g., mirroring or
@@ -3915,20 +3994,17 @@  static void
 patch_port_output(struct xlate_ctx *ctx, const struct xport *in_dev,
                   struct xport *out_dev, bool is_last_action)
 {
-    struct flow *flow = &ctx->xin->flow;
-    struct flow old_flow = ctx->xin->flow;
-    struct flow_tnl old_flow_tnl_wc = ctx->wc->masks.tunnel;
+    struct ovs_list *old_trace = ctx->xin->trace;
     bool old_conntrack = ctx->conntracked;
+    struct flow *flow = &ctx->xin->flow;
     bool old_was_mpls = ctx->was_mpls;
+    struct xretained_state *retained_state;
     ovs_version_t old_version = ctx->xin->tables_version;
-    struct ofpbuf old_stack = ctx->stack;
-    uint8_t new_stack[1024];
-    struct ofpbuf old_action_set = ctx->action_set;
-    struct ovs_list *old_trace = ctx->xin->trace;
-    uint64_t actset_stub[1024 / 8];
 
-    ofpbuf_use_stub(&ctx->stack, new_stack, sizeof new_stack);
-    ofpbuf_use_stub(&ctx->action_set, actset_stub, sizeof actset_stub);
+    retained_state = xretain_state_save(ctx);
+
+    xretain_tunnel_mask_save(ctx, retained_state, out_dev);
+
     flow->in_port.ofp_port = out_dev->ofp_port;
     flow->metadata = htonll(0);
     memset(&flow->tunnel, 0, sizeof flow->tunnel);
@@ -3967,14 +4043,15 @@  patch_port_output(struct xlate_ctx *ctx, const struct xport *in_dev,
         } else {
             /* Forwarding is disabled by STP and RSTP.  Let OFPP_NORMAL and
              * the learning action look at the packet, then drop it. */
-            struct flow old_base_flow = ctx->base_flow;
             size_t old_size = ctx->odp_actions->size;
+
+            xretain_base_flow_save(ctx, retained_state);
             mirror_mask_t old_mirrors2 = ctx->mirrors;
 
             xlate_table_action(ctx, flow->in_port.ofp_port, 0, true, true,
                                false, is_last_action, clone_xlate_actions);
             ctx->mirrors = old_mirrors2;
-            ctx->base_flow = old_base_flow;
+            xretain_base_flow_restore(ctx, retained_state);
             ctx->odp_actions->size = old_size;
 
             /* Undo changes that may have been done for freezing. */
@@ -3986,18 +4063,15 @@  patch_port_output(struct xlate_ctx *ctx, const struct xport *in_dev,
     if (independent_mirrors) {
         ctx->mirrors = old_mirrors;
     }
-    ctx->xin->flow = old_flow;
     ctx->xbridge = in_dev->xbridge;
-    ofpbuf_uninit(&ctx->action_set);
-    ctx->action_set = old_action_set;
-    ofpbuf_uninit(&ctx->stack);
-    ctx->stack = old_stack;
 
     /* Restore calling bridge's lookup version. */
     ctx->xin->tables_version = old_version;
 
-    /* Restore to calling bridge tunneling information */
-    ctx->wc->masks.tunnel = old_flow_tnl_wc;
+    /* Restore to calling bridge tunneling information; the ctx flow, actions,
+     * and stack. And free the retained state. */
+    xretain_tunnel_mask_restore(ctx, retained_state);
+    xretain_state_restore(ctx, retained_state);
 
     /* The out bridge popping MPLS should have no effect on the original
      * bridge. */
@@ -4247,7 +4321,7 @@  compose_output_action__(struct xlate_ctx *ctx, ofp_port_t ofp_port,
     const struct xport *xport = get_ofp_port(ctx->xbridge, ofp_port);
     struct flow_wildcards *wc = ctx->wc;
     struct flow *flow = &ctx->xin->flow;
-    struct flow_tnl flow_tnl;
+    struct flow_tnl *flow_tnl = NULL;
     union flow_vlan_hdr flow_vlans[FLOW_MAX_VLAN_HEADERS];
     uint8_t flow_nw_tos;
     odp_port_t out_port, odp_port, odp_tnl_port;
@@ -4261,7 +4335,6 @@  compose_output_action__(struct xlate_ctx *ctx, ofp_port_t ofp_port,
     /* If 'struct flow' gets additional metadata, we'll need to zero it out
      * before traversing a patch port. */
     BUILD_ASSERT_DECL(FLOW_WC_SEQ == 42);
-    memset(&flow_tnl, 0, sizeof flow_tnl);
 
     if (!check_output_prerequisites(ctx, xport, flow, check_stp)) {
         return;
@@ -4305,7 +4378,8 @@  compose_output_action__(struct xlate_ctx *ctx, ofp_port_t ofp_port,
           * the Logical (tunnel) Port are not visible for any further
           * matches, while explicit set actions on tunnel metadata are.
           */
-        flow_tnl = flow->tunnel;
+        flow_tnl = xmalloc(sizeof *flow_tnl);
+        *flow_tnl = flow->tunnel;
         odp_port = tnl_port_send(xport->ofport, flow, ctx->wc);
         if (odp_port == ODPP_NONE) {
             xlate_report(ctx, OFT_WARN, "Tunneling decided against output");
@@ -4336,7 +4410,7 @@  compose_output_action__(struct xlate_ctx *ctx, ofp_port_t ofp_port,
             tnl_type = tnl_port_get_type(xport->ofport);
             commit_odp_tunnel_action(flow, &ctx->base_flow,
                                      ctx->odp_actions, tnl_type);
-            flow->tunnel = flow_tnl; /* Restore tunnel metadata */
+            flow->tunnel = *flow_tnl; /* Restore tunnel metadata. */
         }
     } else {
         odp_port = xport->odp_port;
@@ -4380,7 +4454,11 @@  compose_output_action__(struct xlate_ctx *ctx, ofp_port_t ofp_port,
             /* Output to native tunnel port. */
             native_tunnel_output(ctx, xport, flow, odp_port, truncate,
                                  is_last_action);
-            flow->tunnel = flow_tnl; /* Restore tunnel metadata */
+            if (flow_tnl) {
+                flow->tunnel = *flow_tnl; /* Restore tunnel metadata. */
+            } else {
+                memset(&flow->tunnel, 0, sizeof flow->tunnel);
+            }
 
         } else if (terminate_native_tunnel(ctx, xport, flow, wc,
                                            &odp_tnl_port)) {
@@ -4423,7 +4501,7 @@  compose_output_action__(struct xlate_ctx *ctx, ofp_port_t ofp_port,
                                          xport->xbundle));
     }
 
- out:
+out:
     /* Restore flow */
     memcpy(flow->vlans, flow_vlans, sizeof flow->vlans);
     flow->nw_tos = flow_nw_tos;
@@ -4431,6 +4509,7 @@  compose_output_action__(struct xlate_ctx *ctx, ofp_port_t ofp_port,
     flow->dl_src = flow_dl_src;
     flow->packet_type = flow_packet_type;
     flow->dl_type = flow_dl_type;
+    free(flow_tnl);
 }
 
 static void
@@ -5874,21 +5953,12 @@  clone_xlate_actions(const struct ofpact *actions, size_t actions_len,
                     struct xlate_ctx *ctx, bool is_last_action,
                     bool group_bucket_action OVS_UNUSED)
 {
-    struct ofpbuf old_stack = ctx->stack;
-    union mf_subvalue new_stack[1024 / sizeof(union mf_subvalue)];
-    ofpbuf_use_stub(&ctx->stack, new_stack, sizeof new_stack);
-    ofpbuf_put(&ctx->stack, old_stack.data, old_stack.size);
-
-    struct ofpbuf old_action_set = ctx->action_set;
-    uint64_t actset_stub[1024 / 8];
-    ofpbuf_use_stub(&ctx->action_set, actset_stub, sizeof actset_stub);
-    ofpbuf_put(&ctx->action_set, old_action_set.data, old_action_set.size);
-
+    struct xretained_state *retained_state;
     size_t offset, ac_offset;
-    struct flow old_flow = ctx->xin->flow;
+
+    retained_state = xretain_state_save(ctx);
 
     if (reversible_actions(actions, actions_len) || is_last_action) {
-        old_flow = ctx->xin->flow;
         do_xlate_actions(actions, actions_len, ctx, is_last_action, false);
         if (!ctx->freezing) {
             xlate_action_set(ctx);
@@ -5903,7 +5973,8 @@  clone_xlate_actions(const struct ofpact *actions, size_t actions_len,
      * avoid emitting those actions twice. Once inside
      * the clone, another time for the action after clone.  */
     xlate_commit_actions(ctx);
-    struct flow old_base = ctx->base_flow;
+    xretain_base_flow_save(ctx, retained_state);
+
     bool old_was_mpls = ctx->was_mpls;
     bool old_conntracked = ctx->conntracked;
 
@@ -5960,14 +6031,10 @@  dp_clone_done:
     ctx->was_mpls = old_was_mpls;
 
     /* Restore the 'base_flow' for the next action.  */
-    ctx->base_flow = old_base;
+    xretain_base_flow_restore(ctx, retained_state);
 
 xlate_done:
-    ofpbuf_uninit(&ctx->action_set);
-    ctx->action_set = old_action_set;
-    ofpbuf_uninit(&ctx->stack);
-    ctx->stack = old_stack;
-    ctx->xin->flow = old_flow;
+    xretain_state_restore(ctx, retained_state);
 }
 
 static void
@@ -6471,19 +6538,13 @@  xlate_check_pkt_larger(struct xlate_ctx *ctx,
         return;
     }
 
-    struct ofpbuf old_stack = ctx->stack;
-    union mf_subvalue new_stack[1024 / sizeof(union mf_subvalue)];
-    ofpbuf_use_stub(&ctx->stack, new_stack, sizeof new_stack);
-    ofpbuf_put(&ctx->stack, old_stack.data, old_stack.size);
+    struct xretained_state *retained_state;
 
-    struct ofpbuf old_action_set = ctx->action_set;
-    uint64_t actset_stub[1024 / 8];
-    ofpbuf_use_stub(&ctx->action_set, actset_stub, sizeof actset_stub);
-    ofpbuf_put(&ctx->action_set, old_action_set.data, old_action_set.size);
+    retained_state = xretain_state_save(ctx);
 
-    struct flow old_flow = ctx->xin->flow;
     xlate_commit_actions(ctx);
-    struct flow old_base = ctx->base_flow;
+    xretain_base_flow_save(ctx, retained_state);
+
     bool old_was_mpls = ctx->was_mpls;
     bool old_conntracked = ctx->conntracked;
 
@@ -6504,10 +6565,10 @@  xlate_check_pkt_larger(struct xlate_ctx *ctx,
     }
     nl_msg_end_nested(ctx->odp_actions, offset_attr);
 
-    ctx->base_flow = old_base;
+    xretain_base_flow_restore(ctx, retained_state);
+    xretain_flow_restore(ctx, retained_state);
     ctx->was_mpls = old_was_mpls;
     ctx->conntracked = old_conntracked;
-    ctx->xin->flow = old_flow;
 
     /* If the flow translation for the IF_GREATER case requires freezing,
      * then ctx->exit would be true. Reset to false so that we can
@@ -6530,15 +6591,11 @@  xlate_check_pkt_larger(struct xlate_ctx *ctx,
     nl_msg_end_nested(ctx->odp_actions, offset_attr);
     nl_msg_end_nested(ctx->odp_actions, offset);
 
-    ofpbuf_uninit(&ctx->action_set);
-    ctx->action_set = old_action_set;
-    ofpbuf_uninit(&ctx->stack);
-    ctx->stack = old_stack;
-    ctx->base_flow = old_base;
     ctx->was_mpls = old_was_mpls;
     ctx->conntracked = old_conntracked;
-    ctx->xin->flow = old_flow;
     ctx->exit = old_exit;
+    xretain_base_flow_restore(ctx, retained_state);
+    xretain_state_restore(ctx, retained_state);
 }
 
 static void
@@ -6989,6 +7046,24 @@  xlate_ofpact_unroll_xlate(struct xlate_ctx *ctx,
                  "cookie=%#"PRIx64, a->rule_table_id, a->rule_cookie);
 }
 
+static void
+xlate_trace(struct xlate_ctx *ctx, const struct ofpact *a) {
+    struct ofputil_port_map map = OFPUTIL_PORT_MAP_INITIALIZER(&map);
+
+    if (ctx->xin->names) {
+        struct ofproto_dpif *ofprotop;
+        ofprotop = ofproto_dpif_lookup_by_name(ctx->xbridge->name);
+        ofproto_append_ports_to_map(&map, ofprotop->up.ports);
+    }
+
+    struct ds s = DS_EMPTY_INITIALIZER;
+    struct ofpact_format_params fp = { .s = &s, .port_map = &map };
+    ofpacts_format(a, OFPACT_ALIGN(a->len), &fp);
+    xlate_report(ctx, OFT_ACTION, "%s", ds_cstr(&s));
+    ds_destroy(&s);
+    ofputil_port_map_destroy(&map);
+}
+
 static void
 do_xlate_actions(const struct ofpact *ofpacts, size_t ofpacts_len,
                  struct xlate_ctx *ctx, bool is_last_action,
@@ -7031,20 +7106,7 @@  do_xlate_actions(const struct ofpact *ofpacts, size_t ofpacts_len,
         }
 
         if (OVS_UNLIKELY(ctx->xin->trace)) {
-            struct ofputil_port_map map = OFPUTIL_PORT_MAP_INITIALIZER(&map);
-
-            if (ctx->xin->names) {
-                struct ofproto_dpif *ofprotop;
-                ofprotop = ofproto_dpif_lookup_by_name(ctx->xbridge->name);
-                ofproto_append_ports_to_map(&map, ofprotop->up.ports);
-            }
-
-            struct ds s = DS_EMPTY_INITIALIZER;
-            struct ofpact_format_params fp = { .s = &s, .port_map = &map };
-            ofpacts_format(a, OFPACT_ALIGN(a->len), &fp);
-            xlate_report(ctx, OFT_ACTION, "%s", ds_cstr(&s));
-            ds_destroy(&s);
-            ofputil_port_map_destroy(&map);
+            xlate_trace(ctx, a);
         }
 
         switch (a->type) {