Hi, We've got a report of a stack overflow on ppc64le with a 16kB kernel stack. Openvswitch is just one of many things in the stack, but it does cause recursion and contributes to some usage.
Here are a few patches for reducing stack overhead. I don't know the code well so consider them just ideas. GFP_ATOMIC allocations introduced in a couple of places might be controversial, but there is still some savings to be had if you skip those. Here is one place detected where the stack reaches >14kB before overflowing a little later. I massaged the output so it just shows the stack frame address on the left. [c00000037d480b40] __kmalloc+0x8c/0x5e0 [c00000037d480bc0] virtqueue_add_outbuf+0x354/0xac0 [c00000037d480cc0] xmit_skb+0x1dc/0x350 [virtio_net] [c00000037d480d50] start_xmit+0xd4/0x3b0 [virtio_net] [c00000037d480e00] dev_hard_start_xmit+0x11c/0x280 [c00000037d480e80] sch_direct_xmit+0xec/0x330 [c00000037d480f20] __dev_xmit_skb+0x41c/0xa80 [c00000037d480f90] __dev_queue_xmit+0x414/0x950 [c00000037d481070] ovs_vport_send+0xb4/0x210 [openvswitch] [c00000037d4810f0] do_output+0x7c/0x200 [openvswitch] [c00000037d481140] do_execute_actions+0xe48/0xeb0 [openvswitch] [c00000037d481300] ovs_execute_actions+0x78/0x1f0 [openvswitch] [c00000037d481380] ovs_dp_process_packet+0xb4/0x2e0 [openvswitch] [c00000037d481450] ovs_vport_receive+0x8c/0x130 [openvswitch] [c00000037d481660] internal_dev_xmit+0x40/0xd0 [openvswitch] [c00000037d481690] dev_hard_start_xmit+0x11c/0x280 [c00000037d481710] __dev_queue_xmit+0x634/0x950 [c00000037d4817f0] neigh_hh_output+0xd0/0x180 [c00000037d481840] ip_finish_output2+0x31c/0x5c0 [c00000037d4818e0] ip_local_out+0x64/0x90 [c00000037d481920] iptunnel_xmit+0x194/0x290 [c00000037d4819c0] udp_tunnel_xmit_skb+0x100/0x140 [udp_tunnel] [c00000037d481a80] geneve_xmit_skb+0x34c/0x610 [geneve] [c00000037d481bb0] geneve_xmit+0x94/0x1e8 [geneve] [c00000037d481c30] dev_hard_start_xmit+0x11c/0x280 [c00000037d481cb0] __dev_queue_xmit+0x634/0x950 [c00000037d481d90] ovs_vport_send+0xb4/0x210 [openvswitch] [c00000037d481e10] do_output+0x7c/0x200 [openvswitch] [c00000037d481e60] do_execute_actions+0xe48/0xeb0 [openvswitch] [c00000037d482020] ovs_execute_actions+0x78/0x1f0 [openvswitch] [c00000037d4820a0] ovs_dp_process_packet+0xb4/0x2e0 [openvswitch] [c00000037d482170] clone_execute+0x2c8/0x370 [openvswitch] [c00000037d482210] do_execute_actions+0x4b8/0xeb0 [openvswitch] [c00000037d4823d0] ovs_execute_actions+0x78/0x1f0 [openvswitch] [c00000037d482450] ovs_dp_process_packet+0xb4/0x2e0 [openvswitch] [c00000037d482520] ovs_vport_receive+0x8c/0x130 [openvswitch] [c00000037d482730] internal_dev_xmit+0x40/0xd0 [openvswitch] [c00000037d482760] dev_hard_start_xmit+0x11c/0x280 [c00000037d4827e0] __dev_queue_xmit+0x634/0x950 [c00000037d4828c0] neigh_hh_output+0xd0/0x180 [c00000037d482910] ip_finish_output2+0x31c/0x5c0 [c00000037d4829b0] __ip_queue_xmit+0x1b0/0x4f0 [c00000037d482a40] __tcp_transmit_skb+0x450/0x9a0 [c00000037d482b10] tcp_write_xmit+0x4e0/0xb40 [c00000037d482be0] __tcp_push_pending_frames+0x44/0x130 [c00000037d482c50] __tcp_sock_set_cork.part.0+0x8c/0xb0 [c00000037d482c80] tcp_sock_set_cork+0x78/0xa0 [c00000037d482cb0] xs_tcp_send_request+0x2d4/0x430 [sunrpc] [c00000037d482e50] xprt_request_transmit.constprop.0+0xa8/0x3c0 [sunrpc] [c00000037d482eb0] xprt_transmit+0x12c/0x260 [sunrpc] [c00000037d482f20] call_transmit+0xd0/0x100 [sunrpc] [c00000037d482f50] __rpc_execute+0xec/0x570 [sunrpc] [c00000037d482fd0] rpc_execute+0x168/0x1d0 [sunrpc] [c00000037d483010] rpc_run_task+0x1cc/0x2a0 [sunrpc] [c00000037d483070] nfs4_call_sync_sequence+0x98/0x100 [nfsv4] [c00000037d483120] _nfs4_server_capabilities+0xd4/0x3c0 [nfsv4] [c00000037d483210] nfs4_server_capabilities+0x74/0xd0 [nfsv4] [c00000037d483270] nfs4_proc_get_root+0x3c/0x150 [nfsv4] [c00000037d4832f0] nfs_get_root+0xac/0x660 [nfs] [c00000037d483420] nfs_get_tree_common+0x104/0x5f0 [nfs] [c00000037d4834b0] nfs_get_tree+0x90/0xc0 [nfs] [c00000037d4834e0] vfs_get_tree+0x48/0x160 [c00000037d483560] nfs_do_submount+0x170/0x210 [nfs] [c00000037d483600] nfs4_submount+0x250/0x360 [nfsv4] [c00000037d4836b0] nfs_d_automount+0x194/0x2d0 [nfs] [c00000037d483710] __traverse_mounts+0x114/0x330 [c00000037d483770] step_into+0x364/0x4d0 [c00000037d4837f0] walk_component+0x8c/0x300 [c00000037d483870] path_lookupat+0xa8/0x260 [c00000037d4838c0] filename_lookup+0xc8/0x230 [c00000037d483a00] vfs_path_lookup+0x68/0xc0 [c00000037d483a60] mount_subtree+0xd0/0x1e0 [c00000037d483ad0] do_nfs4_mount+0x280/0x520 [nfsv4] [c00000037d483ba0] nfs4_try_get_tree+0x60/0x140 [nfsv4] [c00000037d483c20] nfs_get_tree+0x60/0xc0 [nfs] [c00000037d483c50] vfs_get_tree+0x48/0x160 [c00000037d483cd0] do_new_mount+0x204/0x3c0 [c00000037d483d40] sys_mount+0x168/0x1c0 [c00000037d483db0] system_call_exception+0x164/0x310 [c00000037d483e10] system_call_vectored_common+0xe8/0x278 That's hard to decipher so here all the stack frames sorted by size, and number of appearances if > 1: 528 ovs_vport_receive (x2) 448 do_execute_actions (x3) 416 xs_tcp_send_request 320 filename_lookup 304 nfs_get_root 304 geneve_xmit_skb 256 virtqueue_add_outbuf 240 _nfs4_server_capabilities 224 __dev_queue_xmit (x4) 208 tcp_write_xmit 208 __tcp_transmit_skb 208 ovs_dp_process_packet (x3) 208 do_nfs4_mount 192 udp_tunnel_xmit_skb 176 start_xmit 176 nfs4_submount 176 nfs4_call_sync_sequence 160 sch_direct_xmit 160 nfs_do_submount 160 iptunnel_xmit 160 ip_finish_output2 (x2) 160 clone_execute 144 xmit_skb 144 nfs_get_tree_common 144 __ip_queue_xmit 128 walk_component 128 vfs_get_tree (x2) 128 step_into 128 __rpc_execute 128 ovs_vport_send (x2) 128 ovs_execute_actions (x3) 128 nfs4_try_get_tree 128 nfs4_proc_get_root 128 __kmalloc 128 geneve_xmit 128 dev_hard_start_xmit (x4) 112 xprt_transmit 112 __tcp_push_pending_frames 112 sys_mount 112 mount_subtree 112 do_new_mount 112 __dev_xmit_skb 96 xprt_request_transmit.constprop.0 96 vfs_path_lookup 96 __traverse_mounts 96 system_call_exception 96 rpc_run_task 96 nfs_d_automount 96 nfs4_server_capabilities 80 path_lookupat 80 neigh_hh_output (x2) 80 do_output (x2) 64 rpc_execute 64 ip_local_out 48 __tcp_sock_set_cork.part.0 48 tcp_sock_set_cork 48 nfs_get_tree (x2) 48 internal_dev_xmit (x2) 48 call_transmit Thanks, Nick Nicholas Piggin (7): net: openvswitch: Move NSH buffer out of do_execute_actions net: openvswitch: Reduce execute_push_nsh stack overhead net: openvswitch: uninline action execution net: openvswitch: ovs_vport_receive reduce stack usage net: openvswitch: uninline ovs_fragment to control stack usage net: openvswitch: Reduce ovs_fragment stack usage net: openvswitch: Reduce stack usage in ovs_dp_process_packet net/openvswitch/actions.c | 139 +++++++++++++++++++++++-------------- net/openvswitch/datapath.c | 55 ++++++++------- net/openvswitch/drop.h | 1 + net/openvswitch/vport.c | 14 +++- 4 files changed, 129 insertions(+), 80 deletions(-) -- 2.40.1 _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
