[Wrapper-user] Many syscalls per second: EAGAIN (Resource temporarily unavailable)

[Isenberg, H. <ise...@e-...>]

Hallo,

when monitoring the wrapper process with "strace -p Wrapper-PID" on Linux, I'm wondering about the high frequency of read() and recvfrom() calls on the pipe and TCP socket connection to the Java process and each of them returning with "EAGAIN (Resource temporarily unavailable)". The frequency is about 10 per second.

Is this a bug of strace or does the wrapper calls these functions really that fast and why don't they block when waiting for data?

STATUS | wrapper  | 2009/07/10 12:04:50 | --> Wrapper Started as Daemon
STATUS | wrapper  | 2009/07/10 12:04:50 | Java Service Wrapper Standard Edition 64-bit 3.3.5

Linux [...] 2.6.26-2-amd64 #1 SMP Wed Aug 19 22:33:18 UTC 2009 x86_64 GNU/Linux

java version "1.6.0_21"
Java(TM) SE Runtime Environment (build 1.6.0_21-b06)
Java HotSpot(TM) 64-Bit Server VM (build 17.0-b16, mixed mode)

gettimeofday({1280134204, 517914}, NULL) = 0
read(5, 0x7fff030c5130, 1024)           = -1 EAGAIN (Resource temporarily unavailable)
gettimeofday({1280134204, 518004}, NULL) = 0
recvfrom(7, 0x7fff030c554f, 1, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
wait4(30121, 0x7fff030c5544, WNOHANG|WSTOPPED, NULL) = 0
nanosleep({0, 100000000}, NULL)         = 0
gettimeofday({1280134204, 618287}, NULL) = 0
read(5, 0x7fff030c5130, 1024)           = -1 EAGAIN (Resource temporarily unavailable)
gettimeofday({1280134204, 618392}, NULL) = 0
recvfrom(7, 0x7fff030c554f, 1, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
wait4(30121, 0x7fff030c5544, WNOHANG|WSTOPPED, NULL) = 0
nanosleep({0, 100000000}, NULL)         = 0
gettimeofday({1280134204, 718729}, NULL) = 0
read(5, 0x7fff030c5130, 1024)           = -1 EAGAIN (Resource temporarily unavailable)
gettimeofday({1280134204, 718831}, NULL) = 0
recvfrom(7, 0x7fff030c554f, 1, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
wait4(30121, 0x7fff030c5544, WNOHANG|WSTOPPED, NULL) = 0
nanosleep({0, 100000000}, NULL)         = 0
gettimeofday({1280134204, 819092}, NULL) = 0