Niki, On 10/7/13 11:24 AM, Niki Dokovski wrote: > On Mon, Oct 7, 2013 at 5:39 PM, Christopher Schultz < > ch...@christopherschultz.net> wrote: > >> Konstantin, >> >> On 10/7/13 10:24 AM, Konstantin Preißer wrote: >>>> -----Original Message----- >>>> From: Christopher Schultz [mailto:ch...@christopherschultz.net] >>>> Sent: Monday, October 7, 2013 3:29 PM >>>> To: Tomcat Developers List >>>> Subject: Re: 8.0.x / 7.0.x progress >>>> >>>> Konstantin, >>>> >>>> >>>> Note that it's not Tomcat sending the ACKs, but the TCP/IP stack in the >>>> OS running underneath the JVM. I wanted to point that out because it >>>> means that Tomcat may be entirely unaware that data exists for reading >>>> for some reason. If Tomcat itself were sending the ACKs, it would mean >>>> that Tomcat was at least conceptually aware of the data, but refusing to >>>> read it for some reason. >>> >>> Yes, that's correct. I guess there is some buffering in the various >>> layers (TCP/IP stack of OS, Sockets in the JVM etc) so that when sending >>> data, the client receive ACKS with a new window size even if the remote >>> java code might not be reading the data. >> >> Exactly. >> >>> However, the buffering will not be endlessly so at some point TCP >>> will advertise a window of 0 if the java code does not read from the >>> Socket (at least this will be the case with blocking IO - though I do >>> not exactly know how the non-blocking IO is implemented so I may as >>> well be wrong here). This would mean that Firefox will have to wait >>> until there is more window available to continue sending data. >> >> I'm not sure how big the average TCP/IP receive buffer size is. I'd >> suspect a few MBs at least. It's bufferbloat at its finest ;) >> > > The SO_RCVBUF and SO_SNDBUF are system dependent socket options and > typically are in range of 8Kb up to 60Kb. Those are socket level options > though.
I wrote a quick program to check a simple PF_INET/SOCK_STREAM socket's
default buffer sizes.
On my Mac OS X 10.8.5:
SNDBUF=131072 (128k)
RCVBUF=131072 (128k)
On my 64-bit Linux 2.6 kernel:
SNDBUF=16384 (16k)
RCVBUF=87380 (85k)
I don't have a Windows compiler handy, so I couldn't check there.
-chris
PS here's the program in case anyone cares to try it:
#include <stdio.h>
#include <sys/socket.h>
int main(int argc, char *argv[]) {
int sock;
int value;
socklen_t len;
sock = socket(PF_INET, SOCK_STREAM, 0);
len = sizeof(int);
getsockopt(sock, SOL_SOCKET, SO_SNDBUF, &value, &len);
printf("SNDBUF=%d (%dk)\n", value, value/1024);
len = sizeof(int);
getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &value, &len);
printf("RCVBUF=%d (%dk)\n", value, value/1024);
return 0;
}
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