Messages in this thread | | | Date | Mon, 10 Dec 2001 13:11:08 -0700 | From | Ben Greear <> | Subject | Re: min-write-size for a UDP socket to be POLLOUT cannot be set. (proposed fixes) |
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Richard B. Johnson wrote:
> On Mon, 10 Dec 2001, Ben Greear wrote: > > >>This relates to my earlier question about setting the threshold >>at which select returns that a (UDP) socket is writable. >> >>It appears that UDP sockets are hardwired at 2048 bytes... >> >> From linux/include/net/sock.h: >> > > int len = 0x8000; > > setsockopt(s, SOL_SOCKET, SO_SNDBUF, &len, sizeof(len)); > setsockopt(s, SOL_SOCKET, SO_RCVBUF, &len, sizeof(len)); > > > Doesn't this work?
That sets the queue sizes bigger, but suppose this:
I have 4M queue size. I have 4M-2k bytes already in the queue (2k free). I have a 4k UDP buffer to write. I call select and it says the socket is writable. However, in this case I cannot actually write to the socket because I have only 2 of the 4k that I need... Now, I can detect the failure to send and re-transmit, but that basically gets me into a tight loop because select keeps saying I can write, and I keep trying. The tight loop is doubly bad because the machine is already highly stressed or it's buffers would never be so full....
I want select to only say I can write when I'm at XX (say, 64k) bytes of free buffer-queue space...
Ben
> > Cheers, > Dick Johnson > > Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips). > > I was going to compile a list of innovations that could be > attributed to Microsoft. Once I realized that Ctrl-Alt-Del > was handled in the BIOS, I found that there aren't any. > >
-- Ben Greear <greearb@candelatech.com> <Ben_Greear AT excite.com> President of Candela Technologies Inc http://www.candelatech.com ScryMUD: http://scry.wanfear.com http://scry.wanfear.com/~greear
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