Date: Mon, 01 Dec 1997 21:05:33 -0800 From: Amancio Hasty <hasty@rah.star-gate.com> To: Terry Lambert <tlambert@primenet.com> Cc: cmott@srv.net (Charles Mott), hasty@netcom.com, hackers@freebsd.org Subject: Re: ftp server on ftp.cdrom.com Message-ID: <199712020505.VAA01819@rah.star-gate.com> In-Reply-To: Your message of "Tue, 02 Dec 1997 01:02:15 GMT." <199712020102.SAA26394@usr07.primenet.com>
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> > Initially, I was thinking that port 20 data transfers (as opposed to port > > 21 control traffic) had to be either separate processes or threads, but > > now I think you are right -- everything could be done by a synchronous > > state machine in a single user process, but this might be inefficient. > > Unless you used aioread/aiowrite/aiowait/aiocancel from John Dyson's > /sys/kern/vfs_aio.c in -current. Then you could overlap I/O. > > The distinction to be made here is that async I/O and call-conversion > threading mechanisms do not scale on SMP (ie: adding more processors > does not make the work get done any more swiftly). The main drawback > to user space threading mechanisms (like pthreads and user context > management with aio and/or "sigsched", etc.) is SMP and/or cluser > scalability. You are right and that depends on how the I/O subsystem is architected or how low level i/o calls are routed thru the system. For an SMP architecture one could implement multiple state machine servers. Amancio
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