Date: Wed, 28 May 2014 22:02:55 -0700 From: Peter Wemm <peter@wemm.org> To: freebsd-current@freebsd.org Cc: Fred Pedrisa <fredhps10@hotmail.com>, 'Adrian Chadd' <adrian@freebsd.org>, 'Jan Bramkamp' <crest@rlwinm.de> Subject: Re: RES: KQueue vs Select (NetMap) Message-ID: <3223163.UsW4aPcrLi@overcee.wemm.org> In-Reply-To: <COL131-DS2CB7D5481FFC762EA6F10B0240@phx.gbl> References: <COL131-DS24C9EC384D928E5FEB71C3B0240@phx.gbl> <00d301cf7af9$d5ce5bb0$816b1310$@freebsd.org> <COL131-DS2CB7D5481FFC762EA6F10B0240@phx.gbl>
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--nextPart2657138.2G2PXJNEiH Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="us-ascii" On Thursday 29 May 2014 01:57:38 Fred Pedrisa wrote: > Hello, >=20 > 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=20 semantics with kqueue. =20 > -----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) >=20 > If your netmap thread(s) just have one or two FDs in some low range (= say, > under FD 8 or 10) - no. >=20 > If you have a whole bunch of active FDs and your netmap threads get F= Ds 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 inte= rested > 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, sele= ct() > has to check all the FDs in the bitmap to see if they're set before g= etting > to your netmap FD. >=20 > So yes. kqueue() is actually rather nice. >=20 >=20 >=20 > -a >=20 > On 28 May 2014 21:48, Fred Pedrisa <fredhps10@hotmail.com> wrote: > > Hello, > >=20 > > Ok, but in practice, is there any performance gain by moving from s= elect >=20 > to kQueue implementation ? Or is it not significant at all ? >=20 > > -----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) > >=20 > > The advantage is being able to include it in the rest of a kqueue I= O loop >=20 > where it's doing other things. >=20 > > -a > >=20 > > On 28 May 2014 20:53, Fred Pedrisa <fredhps10@hotmail.com> wrote: > >> Hello, > >>=20 > >> Yes, but kqueue support was added in recent commits as it says in = the > >> netmap changelog, is there any advantage ? > >>=20 > >> -----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) > >>=20 > >> On 29.05.2014 03:04, Fred Pedrisa wrote: > >>> Hey Guys, > >>>=20 > >>>=20 > >>>=20 > >>> How does kQueue performs over select with netmap ? > >>=20 > >> 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. > >>=20 > >> The kqueue() and kevent() system calls are an event notification A= PI. > >> It is mostly used by application dealing with a large amount of > >> non-blocking sockets (or other file descriptors). It reduces overh= ead > >> 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.). > >>=20 > >> 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. > >>=20 > >> 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 >=20 > "freebsd-current-unsubscribe@freebsd.org" >=20 > >> _______________________________________________ > >> freebsd-current@freebsd.org mailing list > >> http://lists.freebsd.org/mailman/listinfo/freebsd-current > >> To unsubscribe, send any mail to >=20 > "freebsd-current-unsubscribe@freebsd.org" >=20 > _______________________________________________ > 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" >=20 > _______________________________________________ > 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" =2D-=20 Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI= 6FJV UTF-8: for when a ' just won\342\200\231t do. --nextPart2657138.2G2PXJNEiH Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. 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