Comment 0 for bug 1670959

Sometimes systemd-resolved process is using 100% CPU.
After a while it changes back to normal.

It happens usually after connecting to the (wifi) network, like starting the OS.

strace output:

sendmsg(12, {msg_name(16)={sa_family=AF_INET, sin_port=htons(33589), sin_addr=inet_addr("127.0.0.1")}, msg_iov(1)=[{"6\215\201\200\0\1\0\1\0\0\0\1\4cs41\3wac\vedgecastcdn\3net\0\0\34\0\1\300\f\0\34\0\1\0\0\10\235\0\20&\6(\0\0024\0Y%L\4\6#f&\214\0\0)\377\326\0\0\0\0\0\0", 81}], msg_controllen=28, [{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, {ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("127.0.0.53")}}], msg_flags=0}, 0) = 81
sendmsg(3, {msg_name(0)=NULL, msg_iov(4)=[{"PRIORITY=6\nSYSLOG_FACILITY=3\nCODE_FILE=../src/resolve/resolved-dns-stub.c\nCODE_LINE=363\nCODE_FUNCTION=dns_stub_process_query\nSYSLOG_IDENTIFIER=systemd-resolved\n", 160}, {"MESSAGE=", 8}, {"Processing query...", 19}, {"\n", 1}], msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 188
epoll_wait(4, [{EPOLLIN, {u32=3176459184, u64=94565471415216}}], 16, -1) = 1
clock_gettime(CLOCK_BOOTTIME, {44665, 938069872}) = 0
recvfrom(12, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 53
recvmsg(12, {msg_name(16)={sa_family=AF_INET, sin_port=htons(33589), sin_addr=inet_addr("127.0.0.1")}, msg_iov(1)=[{"Z\262\1\20\0\1\0\0\0\0\0\1\4cs41\3wac\vedgecastcdn\3net\0\0\34\0\1\0\0)\2\0\0\0\0\0\0\0", 3936}], msg_controllen=56, [{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, {ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("127.0.0.53")}}, {cmsg_len=20, cmsg_level=SOL_IP, cmsg_type=IP_TTL, {ttl=64}}], msg_flags=0}, 0) = 53
stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=303, ...}) = 0
getrandom("\365I", 2, GRND_NONBLOCK) = 2
stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=303, ...}) = 0
getrandom("\203;", 2, GRND_NONBLOCK) = 2
clock_gettime(CLOCK_BOOTTIME, {44665, 938446937}) = 0
open("/run/systemd/netif/links/3", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=303, ...}) = 0
stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=303, ...}) = 0
socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 18
connect(18, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 16) = 0
epoll_ctl(4, EPOLL_CTL_ADD, 18, {EPOLLIN, {u32=3176610576, u64=94565471566608}}) = 0
write(18, "\203;\1\20\0\1\0\0\0\0\0\1\4cs41\3wac\vedgecastcdn\3net\0\0\34\0\1\0\0)\2\0\0\0\0\0\0\0", 53) = 53
clock_gettime(CLOCK_BOOTTIME, {44665, 938833717}) = 0
clock_gettime(CLOCK_BOOTTIME, {44665, 938875138}) = 0
epoll_ctl(4, EPOLL_CTL_DEL, 18, NULL) = 0
close(18) = 0

journalctl output:

Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query...
Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query...
Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query...
Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query...
Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query...
Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query...
Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query...
Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query...
Mar 08 08:25:41 parsec dnsmasq[1545]: Maximum number of concurrent DNS queries reached (max: 150)

As you can see, I would use it together with dnsmasq.

ProblemType: Bug
DistroRelease: Ubuntu 17.04
Package: systemd 232-18ubuntu1
ProcVersionSignature: Ubuntu 4.10.0-9.11-generic 4.10.0
Uname: Linux 4.10.0-9-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.20.4-0ubuntu2
Architecture: amd64
Date: Wed Mar 8 08:20:18 2017
MachineType: Hewlett-Packard HP EliteBook Folio 1020 G1
ProcEnviron:
 LANGUAGE=en_US:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/zsh
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-4.10.0-9-generic root=UUID=a54fe703-35d4-47ac-9c6e-4034421531fb ro rootflags=subvol=@
SourcePackage: systemd
UpgradeStatus: Upgraded to zesty on 2015-05-24 (653 days ago)
dmi.bios.date: 03/09/2015
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: M77 Ver. 01.05
dmi.board.name: 2271
dmi.board.vendor: Hewlett-Packard
dmi.board.version: KBC Version 91.4C
dmi.chassis.asset.tag: CNU51199KV
dmi.chassis.type: 10
dmi.chassis.vendor: Hewlett-Packard
dmi.modalias: dmi:bvnHewlett-Packard:bvrM77Ver.01.05:bd03/09/2015:svnHewlett-Packard:pnHPEliteBookFolio1020G1:pvrA3009DD18303:rvnHewlett-Packard:rn2271:rvrKBCVersion91.4C:cvnHewlett-Packard:ct10:cvr:
dmi.product.name: HP EliteBook Folio 1020 G1
dmi.product.version: A3009DD18303
dmi.sys.vendor: Hewlett-Packard