Date: Sun, 11 Apr 2004 23:00:22 -0700 From: Lev Walkin <vlm@netli.com> To: dudu@diaspar.rdsnet.ro Cc: freebsd-hackers@freebsd.org Subject: Re: SYSV message queues Message-ID: <407A3076.8030005@netli.com> In-Reply-To: <20040412011216.P7661@qvnfcne.eqfarg.eb> References: <20040412011216.P7661@qvnfcne.eqfarg.eb>
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Vlad GALU wrote:
> Hello. I have the following scenario: one process that creates a
> message queue and goes through it in a loop, together with another process
> that inserts various messages into the queue. What I wish is for the
> 'listening' process to be able to fully process the queue at a fixed
> amount of time. In short, I'd like msgrcv() to iterate throught the queue
> and visit every element in a single run. That set of operations being done
> periodically.
> Do you find this possible ? I'm quite puzzled here. I first tried
> inserting a sleep() call in my queue processing loop but then I noticed
> that it had a bad effect. It's true that I haven't read the man page very
> carefully the first time. I'll blame it on the hurry.
>
> However, while writing this message, an idea occured to me. What
> if I write the processing loop as follows:
>
> -- cut here --
> int i;
> while (1) {
> i = 0;
> msgctl(queueid, IPC_STAT, &queuestat);
> while (i <= queuestat.msg_qnum) {
> msgrcv(queueid, &message, sizeof(message), 0, 0);
> process_message(message);
> i++;
> }
> sleep(5);
> }
> -- and here --
>
> Does this look pheasible ? I'm expecting an injection of about
> 100k messages per second or even more. There'll be quite a lot of
> unprocessed ones at the end of each run, I suppose. I'll measure the average time spent for
> one run and decide on the sleep interval.
Did you try to grok what the msgrcv() call is supposed to return?
Specifically, read about -1/EAGAIN and IPC_NOWAIT. Then remove sleep().
> However, does anyone have a better design ?
Yes. Use sockets.
Obsolescent Unix IPC Methods
http://www.catb.org/~esr/writings/taoup/html/ch07s03.html#id2923376
--
Lev Walkin
vlm@netli.com
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