Date: Wed, 28 May 2014 22:17:13 -0700 From: Adrian Chadd <adrian@freebsd.org> To: Peter Wemm <peter@wemm.org> Cc: Fred Pedrisa <fredhps10@hotmail.com>, freebsd-current <freebsd-current@freebsd.org>, Jan Bramkamp <crest@rlwinm.de> Subject: Re: RES: KQueue vs Select (NetMap) Message-ID: <CAJ-VmokGG3qxCauz8VvCKE-tTtR-m5jOn=01SEhhfKEVW_GkyA@mail.gmail.com> In-Reply-To: <3223163.UsW4aPcrLi@overcee.wemm.org> References: <COL131-DS24C9EC384D928E5FEB71C3B0240@phx.gbl> <00d301cf7af9$d5ce5bb0$816b1310$@freebsd.org> <COL131-DS2CB7D5481FFC762EA6F10B0240@phx.gbl> <3223163.UsW4aPcrLi@overcee.wemm.org>
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what he said. -a On 28 May 2014 22:02, Peter Wemm <peter@wemm.org> wrote: > On Thursday 29 May 2014 01:57:38 Fred Pedrisa wrote: >> Hello, >> >> There are 4 threads, and a total of 32 FDs. What do you think ? > > I think it is time for you to try it and find out... > > I suspect it wouldn't make much difference at all if you just implement select > semantics with kqueue. > >> -----Mensagem original----- >> De: owner-freebsd-current@freebsd.org >> [mailto:owner-freebsd-current@freebsd.org] Em nome de Adrian Chadd >> Enviada em: quinta-feira, 29 de maio de 2014 01:52 >> Para: Fred Pedrisa >> Cc: freebsd-current; Jan Bramkamp >> Assunto: Re: KQueue vs Select (NetMap) >> >> If your netmap thread(s) just have one or two FDs in some low range (say, >> under FD 8 or 10) - no. >> >> If you have a whole bunch of active FDs and your netmap threads get FDs that >> are high - then yes. select() operates on a bitmap of FD numbers. So if >> your netmap FD is like, FD 8 and it's the highest FD that you're interested >> in, select() only has to scan up to that FD. So it scans up to 8 FDs. If >> you have a very active program and it has thousands of FDs open, select() >> has to check all the FDs in the bitmap to see if they're set before getting >> to your netmap FD. >> >> So yes. kqueue() is actually rather nice. >> >> >> >> -a >> >> On 28 May 2014 21:48, Fred Pedrisa <fredhps10@hotmail.com> wrote: >> > Hello, >> > >> > Ok, but in practice, is there any performance gain by moving from select >> >> to kQueue implementation ? Or is it not significant at all ? >> >> > -----Mensagem original----- >> > De: adrian.chadd@gmail.com [mailto:adrian.chadd@gmail.com] Em nome de >> > Adrian Chadd Enviada em: quinta-feira, 29 de maio de 2014 01:46 >> > Para: Fred Pedrisa >> > Cc: Jan Bramkamp; freebsd-current >> > Assunto: Re: KQueue vs Select (NetMap) >> > >> > The advantage is being able to include it in the rest of a kqueue IO loop >> >> where it's doing other things. >> >> > -a >> > >> > On 28 May 2014 20:53, Fred Pedrisa <fredhps10@hotmail.com> wrote: >> >> Hello, >> >> >> >> Yes, but kqueue support was added in recent commits as it says in the >> >> netmap changelog, is there any advantage ? >> >> >> >> -----Mensagem original----- >> >> De: owner-freebsd-current@freebsd.org >> >> [mailto:owner-freebsd-current@freebsd.org] Em nome de Jan Bramkamp >> >> Enviada em: quinta-feira, 29 de maio de 2014 00:30 >> >> Para: freebsd-current@freebsd.org >> >> Assunto: Re: KQueue vs Select (NetMap) >> >> >> >> On 29.05.2014 03:04, Fred Pedrisa wrote: >> >>> Hey Guys, >> >>> >> >>> >> >>> >> >>> How does kQueue performs over select with netmap ? >> >> >> >> You are asking for a comparison between apples and oranges. Netmap is >> >> an API for high performance access to the low-level features of >> >> modern NICs. It works on batches of frames in hardware queues. >> >> >> >> The kqueue() and kevent() system calls are an event notification API. >> >> It is mostly used by application dealing with a large amount of >> >> non-blocking sockets (or other file descriptors). It reduces overhead >> >> inherent in >> >> select() and poll() by preserving state between calls. It also >> >> supports multiple types of events (read ready, write ready, timer >> >> expired, async i/o, etc.). >> >> >> >> Afaik the netmap pseudo-device supports only select() and poll(). >> >> This is no performance problem because every thread will only deal >> >> with a small number of file descriptors to netmap devices. >> >> >> >> Netmap is designed to bypass the FreeBSD IP stack (for most frames). >> >> Kqueue is designed to scale to many sockets per process within the >> >> FreeBSD IP stack. >> >> _______________________________________________ >> >> freebsd-current@freebsd.org mailing list >> >> http://lists.freebsd.org/mailman/listinfo/freebsd-current >> >> To unsubscribe, send any mail to >> >> "freebsd-current-unsubscribe@freebsd.org" >> >> >> _______________________________________________ >> >> freebsd-current@freebsd.org mailing list >> >> http://lists.freebsd.org/mailman/listinfo/freebsd-current >> >> To unsubscribe, send any mail to >> >> "freebsd-current-unsubscribe@freebsd.org" >> >> _______________________________________________ >> freebsd-current@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-current >> To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >> >> _______________________________________________ >> freebsd-current@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-current >> To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" > > -- > Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV > UTF-8: for when a ' just won\342\200\231t do.
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