On Sun, Mar 06, 2016 at 06:20:06PM -0800, Scott Long wrote: > > > On Mar 6, 2016, at 1:27 PM, Slawa Olhovchenkov <s...@zxy.spb.ru> wrote: > > > > On Sun, Mar 06, 2016 at 01:10:42PM -0800, Scott Long wrote: > > > >> Hi, > >> > >> The message is harmless, it's a reminder that you should tune the kernel > >> for your workload. When the message is triggered, it means that a > >> potential command was deferred, likely for only a few microseconds, and > >> then everything moved on as normal. > >> > >> A command uses anywhere from 0 to a few dozen chain frames per I/o, > >> depending on the size of the io. The chain frame memory is allocated at > >> boot so that it's always available, not allocated on the fly. When I > >> wrote this driver, I felt that it would be wasteful to reserve memory for > >> a worst case scenario of all large io's by default, so I put in this > >> deferral system with a console reminder to for tuning. > >> > >> Yes, you actually do have 900 io's outstanding. The controller buffers > >> the io requests and allows the system to queue up much more than what sata > >> disks might allow on their own. It's debatable if this is good or bad, > >> but it's tunable as well. > >> > >> Anyways, the messages should not cause alarm. Either tune up the chain > >> frame count, or tune down the max io count. > > > > I am don't know depends or not, but I see dramaticaly performance drop > > at time of this messages. > > > > Good to know. Part of the performance drop might be because of the slowness > of printing to the console.
no, on console print may be one per minute > > How I can calculate buffers numbers? > > If your system is new enough to have mpsutil, please run it ‘mpsutil > show iocfacts’. As I see mpsutil present only on -HEAD. Can I compile it on 10-STABLE? > If not, then boot your system with bootverbose and send me the output. I can do this day ago. > > I am have very heavy I/O. > > Out of curiosity, do you redefine MAXPHYS/DFLTPHYS in your kernel config? no > > This allocated one for all controllers, or allocated for every controller? > > It’s per-controller. > > I’ve thought about making the tuning be dynamic at runtime. I > implemented similar dynamic tuning for other drivers, but it seemed > overly complex for low benefit. Implementing it for this driver > would be possible but require some significant code changes. What cause of chain_free+io_cmds_active << max_chains? One cmd can use many chains? _______________________________________________ freebsd-stable@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
