Date: Mon, 9 Nov 1998 11:26:16 -0700 From: Nate Williams <nate@mt.sri.com> To: Marc Slemko <marcs@znep.com> Cc: Nate Williams <nate@mt.sri.com>, hackers@FreeBSD.ORG Subject: Re: Supporting more than FD_SETSIZE fd's Message-ID: <199811091826.LAA05253@mt.sri.com> In-Reply-To: <Pine.BSF.4.05.9811091006510.8174-100000@alive.znep.com> References: <199811091734.KAA04752@mt.sri.com> <Pine.BSF.4.05.9811091006510.8174-100000@alive.znep.com>
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> > I need to support more than the default 255 FD's in an application (the > > JDK for what it's worth). ... > > I looked through the code in Apache, and I don't see how it does this, > > since I never saw any re-definition of FD_SETSIZE, or use of anything > > other than fd_setsize. (Although, I did see mention of FD_SETSIZE quite > > a bit in the comments.) > > Apache doesn't use select() on high numbered descriptors so it doesn't > matter. How does it determine if there is data on those FD's w/out select? I would think that if you have more than 255 active FD's (pretty common) then you'd have a problem. > FD_SETSIZE doesn't limit the number of descriptors, it just limits the > highest descriptor you can pass to select(). Right, hence my question on how other applications deal with the problem, since select doesn't have inherent limitation. > There are various possible workarounds: > > - use poll(). Only on 3.0 unfortunately. > > - on 3.0, FD_SETSIZE defaults to 1024. I'm on 2.2.* > - redefine FD_SETSIZE before including sys/types.h. This may seem to be a > pain, but in most large projects you should have some common header files > you can use for that anyway. This doesn't fix any libraries that you use > though, which may use select() internally with a small FD_SETSIZE. No external libraries are used except for Motif. I'm not sure if it uses Select, but I doubt it. In any case, I'm still defaulting to a larger limit, which is still not a great solution. > Note that Solaris 2.6 is limited to a FD_SETSIZE of 256 (which can't be > changed), so they must have some way around that. Is likely using poll() > though. Solaris/Linux both use poll, which again doesn't exist on 2.2. Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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