Date: Tue, 4 Dec 2012 11:00:25 -0500 From: John Baldwin <jhb@freebsd.org> To: "Steven Hartland" <killing@multiplay.co.uk> Cc: freebsd-scsi@freebsd.org Subject: Re: Changing mfi max_cmds for new tbolt based cards? Message-ID: <201212041100.25693.jhb@freebsd.org> In-Reply-To: <93175830FB964224A4A0B2C4A6C662B3@multiplay.co.uk> References: <93175830FB964224A4A0B2C4A6C662B3@multiplay.co.uk>
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On Friday, November 09, 2012 9:18:17 am Steven Hartland wrote: > I've been doing a lot of work over the past few weeks find and fixing bugs > in the mfi driver. One of these fixes was to ensure that mfi_max_cmds is > used consistently throughout the driver to ensure validation checks work > as expected. > > During this I noticed that mfi_max_cmds is very low for current generation > controllers. In my case 2208 based controller reports 1008 cmd slots, so > quite a jump from the previous max which I believe was 256? > > I was wondering if we should look to change the how our sysctl is setup? > > Recently John you made the following comment: > > Mess with mfi_max_cmds at your own risk. The limit was added to work around > > broken mfi(4) firmware revisions that would lock up when the entire command > > queue (256) was used. Just a suggestion to be cautious. It is probably > > safe to use more than 128, but I would be wary of using all of the slots on > > your adapter. (A verbose boost will show you the number of command slots your > > firmware supports.) > > http://lists.freebsd.org/pipermail/freebsd-current/2012-September/036639.html > > Do you have an information about this specifically:- > 1. Which generation of controller? > 2. Which controller firmware was effected? > 3. Was there a reproducible scenario which triggered this behaviour? > > I'm going to test stability here but my current thinking is to change the > default to -1 (controller limit) for new tbolt based controllers. > > N.B. Resent from correct list account, sorry for the duplicate John. I do not have those details, no. I believe it was seen in earlier mfi(4) adapters such as the parts shipped in Dell PE2950s (though knowing Dell that probably covers a wide range of mfi(4) parts at this point). Scott Long is the one who added the limit in r178968 in May of 2008 (so that gives you a bit of the timeframe for which parts were in vogue then). I do think that the adapters where we saw this hang used 256 command slots (may also help narrow the relevant set of boards down). -- John Baldwin
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