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

[Leif M. <lei...@ta...>]

Holger,
The Wrapper used to be a single threaded application.  Its main loop
still does non-blocking reads on the pipes and sockets. I believe this
is what you are seeing.

Is this causing any problems?  It is possible to change this logic and
use more dedicated threads if necessary.  I would appreciate your
input here.

Cheers,
Leif

On Mon, Jul 26, 2010 at 6:32 PM, Isenberg, Holger <ise...@e-...> wrote:
> 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