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Help with reading strace



Hi

I have a problem with one of my server, where basically I get a
network hang for a few seconds every minute when communicating with
another server on the same subnet.

I caught the hang when running tnsping, and here's the strace. The
space between the strace is where I found the problem to be.

My question is can someone please help wme figure out what is going
on, and guide me to where I can read up on these system calls, like
POLLIN etc. I'd particularly would like to know what is happening
before and after the space in the strace.

recvfrom(4, "\365\335\201\200\0\1\0\1\0\0\0\0\7neptune\2l3\nex"...,
1024, 0, {sa_family=AF_INET, sin_port=htons(53),
sin_addr=inet_addr("10.11.10.1")}, [16]) = 59
close(4)                                = 0
socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 4
connect(4, {sa_family=AF_INET, sin_port=htons(1522),
sin_addr=inet_addr("10.10.8.10")}, 16) = 0
getsockname(4, {sa_family=AF_INET, sin_port=htons(34882),
sin_addr=inet_addr("10.10.8.24")}, [16]) = 0
setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0
fcntl64(4, F_SETFD, FD_CLOEXEC)         = 0
rt_sigaction(SIGPIPE, {SIG_IGN}, {SIG_IGN}, 8) = 0
getpid()                                = 15414
gettimeofday({1143022459, 867628}, NULL) = 0
gettimeofday({1143022459, 867674}, NULL) = 0
write(4, "\0W\0\0\1\0\0\0\0018\1,\0\0\10\0\177\377\177\10\0\0\1\0"..., 87) = 87
read(4, "\0J\0\0\4\0\0\0\"\0\0>(DESCRIPTION=(TMP=)("..., 2064) = 74
close(4)                                = 0
gettimeofday({1143022459, 868207}, NULL) = 0
write(1, "OK (0 msec)\n", 12)           = 12
gettimeofday({1143022459, 868364}, NULL) = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 4
connect(4, {sa_family=AF_FILE, path="/var/run/.nscd_socket"}, 110) =
-1 ENOENT (No such file or directory)
close(4)                                = 0
open("/etc/hosts", O_RDONLY)            = 4
fcntl64(4, F_GETFD)                     = 0
fcntl64(4, F_SETFD, FD_CLOEXEC)         = 0
fstat64(4, {st_mode=S_IFREG|0644, st_size=310, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
0) = 0xb75b1000
read(4, "# Do not remove the following li"..., 4096) = 310
read(4, "", 4096)                       = 0
close(4)                                = 0
munmap(0xb75b1000, 4096)                = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 4
connect(4, {sa_family=AF_INET, sin_port=htons(53),
sin_addr=inet_addr("10.11.10.1")}, 28) = 0
fcntl64(4, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(4, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1143022459, 869414}, NULL) = 0
poll([{fd=4, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
send(4, "\367\201\1\0\0\1\0\0\0\0\0\0\7neptune\2l3\next"..., 43, 0) = 43
poll(





[{fd=4, events=POLLIN}], 1, 5000)  = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 5
connect(5, {sa_family=AF_INET, sin_port=htons(53),
sin_addr=inet_addr("10.11.10.2")}, 28) = 0
fcntl64(5, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(5, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1143022464, 877593}, NULL) = 0
poll([{fd=5, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
send(5, "\367\201\1\0\0\1\0\0\0\0\0\0\7neptune\2l3\next"..., 43, 0) = 43
poll([{fd=5, events=POLLIN, revents=POLLIN}], 1, 5000) = 1
ioctl(5, FIONREAD, [59])                = 0
recvfrom(5, "\367\201\201\200\0\1\0\1\0\0\0\0\7neptune\2l3\nex"...,
1024, 0, {sa_family=AF_INET, sin_port=htons(53),
sin_addr=inet_addr("10.11.10.2")}, [16]) = 59
close(4)                                = 0
close(5)                                = 0
socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 4
connect(4, {sa_family=AF_INET, sin_port=htons(1522),
sin_addr=inet_addr("10.10.8.10")}, 16) = 0
getsockname(4, {sa_family=AF_INET, sin_port=htons(34883),
sin_addr=inet_addr("10.10.8.24")}, [16]) = 0
setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0
fcntl64(4, F_SETFD, FD_CLOEXEC)         = 0
rt_sigaction(SIGPIPE, {SIG_IGN}, {SIG_IGN}, 8) = 0
getpid()                                = 15414
gettimeofday({1143022464, 879441}, NULL) = 0
gettimeofday({1143022464, 879487}, NULL) = 0
write(4, "\0W\0\0\1\0\0\0\0018\1,\0\0\10\0\177\377\177\10\0\0\1\0"..., 87) = 87
read(4, "\0J\0\0\4\0\0\0\"\0\0>(DESCRIPTION=(TMP=)("..., 2064) = 74
close(4)                                = 0
gettimeofday({1143022464, 879991}, NULL) = 0
write(1, "OK (5010 msec)\n", 15)        = 15
gettimeofday({1143022464, 880104}, NULL) = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 4
connect(4, {sa_family=AF_FILE, path="/var/run/.nscd_socket"}, 110) =
-1 ENOENT (No such file or directory)
close(4)                                = 0
open("/etc/hosts", O_RDONLY)            = 4
fcntl64(4, F_GETFD)                     = 0
fcntl64(4, F_SETFD, FD_CLOEXEC)         = 0
fstat64(4, {st_mode=S_IFREG|0644, st_size=310, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
0) = 0xb75b1000



Thanks for your help
Dan


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