Date: Fri, 27 Oct 2017 09:06:59 -0600 From: Warner Losh <imp@bsdimp.com> To: Alan Somers <asomers@freebsd.org> Cc: Warner Losh <imp@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r325026 - head/sys/cam/ata Message-ID: <CANCZdfr0RRzgudknQUz89c2qT5JPG%2B2W4_NPpfjoiBY8DYAtEA@mail.gmail.com> In-Reply-To: <CAOtMX2imPCLyH2rW=0cZu4VJ-RYnfbmjSzSHr45aUTJdUCzrcQ@mail.gmail.com> References: <201710262253.v9QMrovZ009495@repo.freebsd.org> <CAOtMX2gFAj-yQzG6pwNmjAWYaw8_o3RHRfiAVURfNd7ib-BFZg@mail.gmail.com> <CANCZdfpg0MK_Smui%2B=7SWwBdJbCURJiyoXii4DXpnTP0K-wO9w@mail.gmail.com> <CANCZdfp5=Q1%2BYcPhC1fDHBZqCoVAUf8%2BtZQGboCOsUaHjmpz1A@mail.gmail.com> <CAOtMX2imPCLyH2rW=0cZu4VJ-RYnfbmjSzSHr45aUTJdUCzrcQ@mail.gmail.com>
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On Fri, Oct 27, 2017 at 8:50 AM, Alan Somers <asomers@freebsd.org> wrote: > On Thu, Oct 26, 2017 at 8:27 PM, Warner Losh <imp@bsdimp.com> wrote: > > > > > > On Thu, Oct 26, 2017 at 5:35 PM, Warner Losh <imp@bsdimp.com> wrote: > >> > >> > >> > >> On Thu, Oct 26, 2017 at 5:04 PM, Alan Somers <asomers@freebsd.org> > wrote: > >>> > >>> On Thu, Oct 26, 2017 at 4:53 PM, Warner Losh <imp@freebsd.org> wrote: > >>> > Author: imp > >>> > Date: Thu Oct 26 22:53:49 2017 > >>> > New Revision: 325026 > >>> > URL: https://svnweb.freebsd.org/changeset/base/325026 > >>> > > >>> > Log: > >>> > Always send STANDBY IMMEDIATE when shutting down > >>> > > >>> > To save SMART data and for a drive to understand that it's been > >>> > nicely > >>> > shutdown, we need to send a STANDBY IMMEDIATE. Modify adaspindown > to > >>> > use a local CCB on the stack. When we're panicing, used > >>> > xpt_polled_action rather than cam_periph_runccb so that we can SEND > >>> > IMMEDIATE after we've shutdown the scheduler. > >>> > > >>> > Sponsored by: Netflix > >>> > Reviewed by: scottl@, gallatin@ > >>> > Differential Revision: https://reviews.freebsd.org/D12799 > >>> > > >>> > Modified: > >>> > head/sys/cam/ata/ata_da.c > >>> > >>> Will this put the drive into a standby state just prior to a warm > >>> reboot? That could cause lengthy delays on the new boot while the > >>> drives spin up. That behavior caused a problem when the mpr driver > >>> did it to a JBOD full of 96 SATA drives. On the new boot, each drive > >>> spun up one at a time while they were being probed. Eventually the > >>> system paniced because run_interrupt_driven_hooks timed out. With > >>> mpr, I was able to fix the problem by setting hw.mpr.enable_ssu=0. > >> > >> > >> That's a good question. The standard is silent about what, exactly, the > >> Standby state means. We already allow this to be disabled, and this > commit > >> doesn't change that. It looks like IDLE IMMEDIATE also forces SMART > media > >> non volatile to be flushed out. > >> > >> What do you suggest? > > > > > > I see two paths forward. We need to flush the NV SMART data at reboot > time. > > SSDs that we use, at least, consider it an unclean shutdown if you don't > > Idle the drive on reboot because part of that process does a > > COMINIT/COMRESET and if the drive is in the Active state, it ticks up the > > counter (and with at least one vendor can lose NV SMART data). > > > > So, path forward #1 is that we do STANDBY IMMEDIATE for SSDs in the > > RB_REBOOT case or all drives in the other cases. For HDD and RB_REBOOT > we do > > only a IDLE IMMEDIATE which shouldn't spin the drives down. This seems to > > bake in what we know about storage devices and is easiest for the user. > If > > we get it right, it's easier for the user. If we get it wrong, the user > can > > disable all spin downs. > > > > Path forward #2 is to just make what we send a sysctl. This is > unsatisfying > > and error-prone, but gives the most flexibility. I don't like this. > > > > I'd be curious if there's another viable path forward I'm not seeing that > > you might know. > > > > FWIW, we don't connect HDDs to our AHCI ports (they are all on > MPT/MPS/MPR > > HBAs), so we've not seen any issues in the 6 or so months we've had this > in > > the tree. > > > > Warner > > Is there some reason not to send IDLE IMMEDIATE to both SSDs and HDDs? > On warm boot? Not that I can think of. Our drive vendor told us specifically that STANDBY IMMEDIATE was what we should use, so I'll have to do some research. The standard says that it should be fine though. I like that direction. For the other stuff, I think we should still send STANDBY IMMEDIATE. I'll work up a patch (the hardest part is the comment) and add you to the review later today. Warner
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