Date: Sat, 13 Jan 2007 14:41:54 -0500 From: Kris Kennaway <kris@obsecurity.org> To: Michel Santos <michel@lucenet.com.br> Cc: freebsd-performance@freebsd.org, Mark Kirkwood <markir@paradise.net.nz>, Kris Kennaway <kris@obsecurity.org> Subject: Re: diskio low read performance Message-ID: <20070113194154.GA65864@xor.obsecurity.org> In-Reply-To: <64716.200.152.83.36.1168716219.squirrel@webmail.matik.com.br> References: <64656.200.152.83.36.1168651673.squirrel@webmail.matik.com.br> <45A87878.1050505@paradise.net.nz> <63758.200.152.83.36.1168689227.squirrel@webmail.matik.com.br> <20070113164232.GA34348@xor.obsecurity.org> <64857.200.152.83.36.1168710081.squirrel@webmail.matik.com.br> <20070113180036.GA64359@xor.obsecurity.org> <60639.200.152.83.36.1168714686.squirrel@webmail.matik.com.br> <20070113190447.GA65571@xor.obsecurity.org> <64716.200.152.83.36.1168716219.squirrel@webmail.matik.com.br>
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--HlL+5n6rz5pIUxbD Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Jan 13, 2007 at 05:23:39PM -0200, Michel Santos wrote: > >> kernel config > >> http://suporte.lucenet.com.br/ms/kernel62 > > > > options SCHED_ULE # ULE scheduler > > > > From the NOTES file from where you copied this: > > > > # SCHED_ULE is a new scheduler that has been designed for SMP and has s= ome > > # advantages for UP as well. It is intended to replace the 4BSD schedu= ler > > # over time. NOTE: SCHED_ULE is currently considered experimental and = is > > # not recommended for production use at this time. > > > > When investigating problems with your system, your very first step > > should be to revert the use of code marked "experimental" and "not > > recommended for production use" ;-) > > >=20 > I am running both (on at a time of course :) ), now for six month or so, > ULE is giving me better overall performance, either with or w/o polling. I > mean network performance. I have net.isr.enable=3D1 and > net.inet.ip.fastforwarding=3D1, > this way I do get the same network performance I had on the 4.11. I mean I > have no problem here. >=20 > But also I checked the ULE/BSD against my particular problem and there is > no difference at all. I get no acceptable disk read performance when > comparing what I had with 4.11, wether with ULE or with 4BSD Be very careful, because I've personally measured severe disk I/O penalties with ULE on SMP hardware. In fact in my testing ULE gives worse SMP performance under load across the board compared to 4BSD (it's only faster for the lightest of workloads). If you're absolutely certain that ULE is not to blame (and want to continue to take the risk of other performance and stability problems down the line), that basically leaves something to do with the scsi driver and/or its interaction with your hardware as the probable cause. I don't know enough about this particular hardware to comment further though. Some other comments about your config that are not likely to be relevant for your I/O problem: * it's not recommended to use an explicit maxusers value unless you know that you need it; modern versions of FreeBSD auto-tune with maxusers 0 which is the recommended configuration. * adaptive mutexes are usually a win so it's a bit unusual that you have disabled them, but I assume you have tested this. * Dunno about the AUTO_EOI_1 option, I don't think you even have this hardware on your system (device atpic didn't probe in your dmesg). * HZ=3D1000 is superfluous since it is the default but may or may not help. In some workloads the increased overhead relative to the old default of HZ=3D100 gives a performance loss. Maybe it helps with polling though, I dunno. Kris --HlL+5n6rz5pIUxbD Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (FreeBSD) iD8DBQFFqTYCWry0BWjoQKURAkXNAKCXT3Xgg2Uph0U7H48XI29uy5yFkACfWJHm /uNORKz65sTB4zg65tHW5fw= =kUqf -----END PGP SIGNATURE----- --HlL+5n6rz5pIUxbD--
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