Date: Thu, 4 Sep 2008 01:46:42 +0200 From: Bernd Walter <ticso@cicely7.cicely.de> To: David Malone <dwmalone@maths.tcd.ie> Cc: Bernd Walter <ticso@cicely7.cicely.de>, freebsd-current@freebsd.org, ticso@cicely.de Subject: Re: MTRR fixup? Message-ID: <20080903234642.GA14659@cicely7.cicely.de> In-Reply-To: <20080903204759.GA4898@walton.maths.tcd.ie> References: <20080903034943.GD11548@cicely7.cicely.de> <20080903204759.GA4898@walton.maths.tcd.ie>
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On Wed, Sep 03, 2008 at 09:47:59PM +0100, David Malone wrote: > On Wed, Sep 03, 2008 at 05:49:44AM +0200, Bernd Walter wrote: > > Some boards (including my Intel DG33BU) seem to have problems setting > > up the mtrr to cache all RAM. > > My system runs fast with 2G and ist about 6 times slower in buildworld > > with 6G RAM. > > I will try a BIOS update once Intels tells me why their update ISO > > just turn the system off instead of updating the BIOS - sigh. > > But it seems that Linux is doing some kind of fixup for MTRR: > > http://lkml.org/lkml/2008/1/18/170 > > Can we do something similar? > > You may be able to fix this by just using the memcontrol command - > it already lets you program the MTRRs. Oh damn - a new fancy tool to play with ;-) Interesting - the values look good: [...] 0x0/0x80000000 ticso write-back active 0x80000000/0x40000000 ticso write-back active 0xc0000000/0x10000000 ticso write-back active 0xcf800000/0x800000 BIOS uncacheable set-by-firmware active 0xcf400000/0x400000 BIOS uncacheable set-by-firmware active 0x100000000/0x80000000 ticso write-back active 0x180000000/0x20000000 ticso write-back active 0x0/0x1000000000 - uncacheable I've already overwritten it for tests, but it was the same as left by the BIOS. If I set everything uncacheable the system slows down by a factor of two - measured from top CPU usage seen in top. If I set it back to write-back it returns to previous usage, but it is still much slower than with 2G installed. Maybe MTRR is a red hering... But why are the Linux guys claim to fix this with MTRR settings? -- B.Walter <bernd@bwct.de> http://www.bwct.de Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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