Date: Mon, 22 Mar 2010 11:11:55 -0400 From: jhell <jhell@DataIX.net> To: Alexander Motin <mav@freebsd.org> Cc: FreeBSD-Current <freebsd-current@freebsd.org>, freebsd-arch@freebsd.org Subject: Re: Increasing MAXPHYS Message-ID: <alpine.BSF.2.00.1003221110120.63287@pragry.qngnvk.ybpny> In-Reply-To: <4BA705CB.9090705@FreeBSD.org> References: <4BA4E7A9.3070502@FreeBSD.org> <201003201753.o2KHrH5x003946@apollo.backplane.com> <891E2580-8DE3-4B82-81C4-F2C07735A854@samsco.org> <4BA52179.9030903@FreeBSD.org> <4BA532FF.6040407@elischer.org> <4BA62757.7090400@FreeBSD.org> <alpine.BSF.2.00.1003212045540.16103@qvfongpu.qngnvk.ybpny> <alpine.BSF.2.00.1003212158190.16103@qvfongpu.qngnvk.ybpny> <4BA705CB.9090705@FreeBSD.org>
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On Mon, 22 Mar 2010 01:53, Alexander Motin wrote: In Message-Id: <4BA705CB.9090705@FreeBSD.org> > jhell wrote: >> On Sun, 21 Mar 2010 20:54, jhell@ wrote: >>> I played with it on one re-compile of a kernel and for the sake of it >>> DFLTPHYS=128 MAXPHYS=256 and found out that I could not cause a crash >>> dump to be performed upon request (reboot -d) due to the boundary >>> being hit for DMA which is 65536. Obviously this would have to be >>> adjusted in ata-dma.c. >>> >>> I suppose that there would have to be a better way to get the real >>> allowable boundary from the running system instead of setting it >>> statically. >>> >>> Other then the above I do not see a reason why not... It is HEAD and >>> this is the type of experimental stuff it was meant for. >> >> I should have also said that I also repeated the above without setting >> DFLTPHYS and setting MAXPHYS to 256. > > It was bad idea to increase DFLTPHYS. It is not intended to be increased. > I just wanted to see what I could break; when I increased DFLTPHYS it was just for that purpose. It booted and everything was running after. Wasn't long enough to do any damage. > About DMA boundary, I do not very understand the problem. Yes, legacy > ATA has DMA boundary of 64K, but there is no problem to submit S/G list > of several segments. How long ago have you tried it, on which controller > and which diagnostics do you have? > > atapci0@pci0:0:31:1: class=0x01018a card=0x01271028 chip=0x24cb8086 rev=0x01 hdr=0x00 vendor = 'Intel Corporation' device = '82801DB/DBL (ICH4/ICH4-L) UltraATA/100 EIDE Controller' class = mass storage subclass = ATA I do not have any diagnostics but if any are requested I do have the kernel's that I have tuned to the above values readily available to run again. The first time I tuned MAXPHYS was roughly about 7 weeks ago. That was until I noticed I could not get a crash dump for a problem I was having a week later and had to revert back to its default setting of 128. The problem I had a week later was unrelated. Two days ago when I saw this thread I recalled having modified MAXPHYS but could not remember the problem it caused so I re-enabled it again to reproduce the problem for sureness. Anything else you need please address, Regards, -- jhell
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