1$NetBSD: TODO.smpnet,v 1.19 2018/02/27 14:28:01 maxv Exp $ 2 3MP-safe components 4================== 5 6 - Device drivers 7 - vioif(4) 8 - vmx(4) 9 - wm(4) 10 - ixg(4) 11 - ixv(4) 12 - Layer 2 13 - Ethernet (if_ethersubr.c) 14 - bridge(4) 15 - STP 16 - Fast forward (ipflow) 17 - Layer 3 18 - All except for items in the below section 19 - Interfaces 20 - gif(4) 21 - l2tp(4) 22 - pppoe(4) 23 - if_spppsubr.c 24 - tun(4) 25 - vlan(4) 26 - Packet filters 27 - npf(7) 28 - Others 29 - bpf(4) 30 - ipsec(4) 31 - opencrypto(9) 32 - pfil(9) 33 34Non MP-safe components and kernel options 35========================================= 36 37 - Device drivers 38 - Most drivers other than ones listed in the above section 39 - Layer 2 40 - ARCNET (if_arcsubr.c) 41 - ATM (if_atmsubr.c) 42 - BRIDGE_IPF 43 - FDDI (if_fddisubr.c) 44 - HIPPI (if_hippisubr.c) 45 - IEEE 1394 (if_ieee1394subr.c) 46 - IEEE 802.11 (ieee80211(4)) 47 - Token ring (if_tokensubr.c) 48 - Layer 3 49 - IPSELSRC 50 - MROUTING 51 - PIM 52 - MPLS (mpls(4)) 53 - IPv6 address selection policy 54 - Layer 4 55 - DCCP 56 - SCTP 57 - TCP 58 - UDP 59 - Interfaces 60 - agr(4) 61 - carp(4) 62 - etherip(4) 63 - faith(4) 64 - gre(4) 65 - ppp(4) 66 - sl(4) 67 - stf(4) 68 - strip(4) 69 - if_srt 70 - tap(4) 71 - Packet filters 72 - ipf(4) 73 - pf(4) 74 - Others 75 - AppleTalk (sys/netatalk/) 76 - ATM (sys/netnatm/) 77 - Bluetooth (sys/netbt/) 78 - altq(4) 79 - CIFS (sys/netsmb/) 80 - ISDN (sys/netisbn/) 81 - kttcp(4) 82 - NFS 83 84Know issues 85=========== 86 87NOMPSAFE 88-------- 89 90We use "NOMPSAFE" as a mark that indicates that the code around it isn't MP-safe 91yet. We use it in comments and also use as part of function names, for example 92m_get_rcvif_NOMPSAFE. Let's use "NOMPSAFE" to make it easy to find non-MP-safe 93codes by grep. 94 95bpf 96--- 97 98MP-ification of bpf requires all of bpf_mtap* are called in normal LWP context 99or softint context, i.e., not in hardware interrupt context. For Tx, all 100bpf_mtap satisfy the requrement. For Rx, most of bpf_mtap are called in softint. 101Unfortunately some bpf_mtap on Rx are still called in hardware interrupt context. 102 103This is the list of the functions that have such bpf_mtap: 104 105 - sca_frame_process() @ sys/dev/ic/hd64570.c 106 - en_intr() @ sys/dev/ic/midway.c 107 - rxintr_cleanup() and txintr_cleanup() @ sys/dev/pci/if_lmc.c 108 - ipr_rx_data_rdy() @ sys/netisdn/i4b_ipr.c 109 110Ideally we should make the functions run in softint somehow, but we don't have 111actual devices, no time (or interest/love) to work on the task, so instead we 112provide a deferred bpf_mtap mechanism that forcibly runs bpf_mtap in softint 113context. It's a workaround and once the functions run in softint, we should use 114the original bpf_mtap again. 115 116Lingering obsolete variables 117----------------------------- 118 119Some obsolete global variables and member variables of structures remain to 120avoid breaking old userland programs which directly access such variables via 121kvm(3). 122 123The following programs still use kvm(3) to get some information related to 124the network stack. 125 126 - netstat(1) 127 - vmstat(1) 128 - fstat(1) 129 130netstat(1) accesses ifnet_list, the head of a list of interface objects 131(struct ifnet), and traverses each object through ifnet#if_list member variable. 132ifnet_list and ifnet#if_list is obsoleted by ifnet_pslist and 133ifnet#if_pslist_entry respectively. netstat also accesses the IP address list 134of an interface throught ifnet#if_addrlist. struct ifaddr, struct in_ifaddr 135and struct in6_ifaddr are accessed and the following obsolete member variables 136are stuck: ifaddr#ifa_list, in_ifaddr#ia_hash, in_ifaddr#ia_list, 137in6_ifaddr#ia_next and in6_ifaddr#_ia6_multiaddrs. Note that netstat already 138implements alternative methods to fetch the above information via sysctl(3). 139 140vmstat(1) shows statistics of hash tables created by hashinit(9) in the kernel. 141The statistic information is retrieved via kvm(3). The global variables 142in_ifaddrhash and in_ifaddrhashtbl, which are for a hash table of IPv4 143addresses and obsoleted by in_ifaddrhash_pslist and in_ifaddrhashtbl_pslist, 144are kept for this purpose. We should provide a means to fetch statistics of 145hash tables via sysctl(3). 146 147fstat(1) shows information of bpf instances. Each bpf instance (struct bpf) is 148obtained via kvm(3). bpf_d#_bd_next, bpf_d#_bd_filter and bpf_d#_bd_list 149member variables are obsolete but remain. ifnet#if_xname is also accessed 150via struct bpf_if and obsolete ifnet#if_list is required to remain to not change 151the offset of ifnet#if_xname. The statistic counters (bpf#bd_rcount, 152bpf#bd_dcount and bpf#bd_ccount) are also victims of this restriction; for 153scalability the statistic counters should be per-CPU and we should stop using 154atomic operations for them however we have to remain the counters and atomic 155operations. 156 157Scalability 158----------- 159 160 - Per-CPU rtcaches (used in say IP forwarding) aren't scalable on multiple 161 flows per CPU 162 - ipsec(4) isn't scalable on the number of SA/SP; the cost of a look-up 163 is O(n) 164 - opencrypto(9)'s crypto_newsession()/crypto_freesession() aren't scalable 165 as they are serialized by one mutex 166 167ec_multi* of ethercom 168--------------------- 169 170ec_multiaddrs and ec_multicnt of struct ethercom and items listed in 171ec_multiaddrs must be protected by ec_lock. The core of ethernet subsystem is 172already MP-safe, however, device drivers that use the data should also be fixed. 173A typical change should be to protect manipulations of the data via ETHER_* 174macros such as ETHER_FIRST_MULTI by ETHER_LOCK and ETHER_UNLOCK. 175 176ALTQ 177---- 178 179If ALTQ is enabled in the kernel, it enforces to use just one Tx queue (if_snd) 180for packet transmissions, resulting in serializing all Tx packet processing on 181the queue. We should probably design and implement an alternative queuing 182mechanism that deals with multi-core systems at the first place, not making the 183existing ALTQ MP-safe because it's just annoying. 184