On Tue, Jan 06, 2015 at 09:37:30AM -0500, John Baldwin wrote:
> On 1/5/15 8:18 AM, Hans Petter Selasky wrote:
> > Hi,
> >
> > There is a limitiation on the number of interrupt vectors available when
> > only a single processor is running. To have more interrupts available we
> > need to start SMP earlier when building a monotolith kernel and not
> > loading drivers as modules. The driver in question is a network driver
> > and because it cannot be started after SI_SUB_ROOT_CONF due to PXE
> > support I see no other option than to move SI_SUB_SMP earlier.
> >
> > Suggested patch:
> >
> >> Index: sys/kernel.h
> >> ===================================================================
> >> --- sys/kernel.h (revision 276691)
> >> +++ sys/kernel.h (working copy)
> >> @@ -152,6 +152,7 @@
> >> SI_SUB_KPROF = 0x9000000, /* kernel profiling*/
> >> SI_SUB_KICK_SCHEDULER = 0xa000000, /* start the timeout
> >> events*/
> >> SI_SUB_INT_CONFIG_HOOKS = 0xa800000, /* Interrupts enabled
> >> config */
> >> + SI_SUB_SMP = 0xa850000, /* start the APs*/
> >> SI_SUB_ROOT_CONF = 0xb000000, /* Find root devices */
> >> SI_SUB_DUMP_CONF = 0xb200000, /* Find dump devices */
> >> SI_SUB_RAID = 0xb380000, /* Configure GEOM classes */
> >> @@ -165,7 +166,6 @@
> >> SI_SUB_KTHREAD_BUF = 0xea00000, /* buffer daemon*/
> >> SI_SUB_KTHREAD_UPDATE = 0xec00000, /* update daemon*/
> >> SI_SUB_KTHREAD_IDLE = 0xee00000, /* idle procs*/
> >> - SI_SUB_SMP = 0xf000000, /* start the APs*/
> >> SI_SUB_RACCTD = 0xf100000, /* start racctd*/
> >> SI_SUB_LAST = 0xfffffff /* final initialization */
> >> };
> >
> > This fixes a problem for Mellanox drivers in the OFED layer. Possibly we
> > need to move the SMP even earlier to not miss the generic FreeBSD PCI
> > device enumeration or maybe this is not possible. Does anyone know how
> > early we can start SMP?
>
> We need a lot more work before this is ready. This is one of the goals
> of the multipass new-bus stuff. In particular, we have to enumerate
> enough devices to bring event timer hardware up so that timer interrupts
> work so that tsleep() will actually sleep. In addition, we also need
> idle threads created and working before APs are started as otherwise
> they will have no thread to run initially. This is certainly a desired
> feature, but it is not as simple as moving the sysinit up I'm afraid.
>
I believe that idle threads are still created before the APs start
with the patch posted, this was the thing I checked first. It is
SUB_SCHED_IDLE, which is done long before even drivers are configured.
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