On Tue, Oct 07, 2025 at 05:33:35PM +1000, Jonathan Matthew wrote:
> On Sat, Sep 27, 2025 at 06:36:50PM +0200, Alexander Bluhm wrote:
> > Hi,
> > 
> > Currently most network drivers use 8 queues and distribute interrupts.
> > ix(4) is the only one that may allocate more than 8.  ice(8) uses
> > only 8 vectors, but allocates more interrupts.
> > 
> > I would like to limit interrupts and queues to 8 for all drivers.
> > This prevents running out of interrupt vectors so easily.  Currently
> > we have 8 softnet threads which limits parallel processing anyway.
> > We can tune these values later.
> > 
> > With this diff, forwarding througput increases from 45 to 50 GBit/sec
> > on my 12 core machine from ice0 to ice1.  I am using iperf3 TCP on
> > Linux to measure it.  I think slower performance happend because
> > ice(4) was allocating more interrupts than it has vectors.  Now
> > everything is limited to 8.  For other drivers I see no difference
> > as they operate at line speed anyway.
> > 
> > I think arbitrary numbers IXL_MAX_VECTORS, IGC_MAX_VECTORS and
> > IGC_MAX_VECTORS could go away, but that would be per driver diffs.
> 
> I think the changes to bnxt, igc and ixl, where you're just picking the
> smaller of two constants, neither of which reflects an actual limit on
> the number of queues available, should be removed from the diff.
> We've mostly settled on 8 as the maximum number of queues to use anyway,
> so this doesn't really change anything.

Are there any hardware limits?  As I want to play with IF_MAX_VECTORS
globally, it would be nice to know the capabilites of the hardware.
That's why I wanted to address this on a per driver basis.

igc(4) says
#define IGC_MAX_VECTORS                8
without explanation.  Is this an actual hardware limit?

ix has these lines
        /* XXX the number of queues is limited to what we can keep stats on */
        maxq = (sc->hw.mac.type == ixgbe_mac_82598EB) ? 8 : 16;

Are the 8 and 16 restrictions of the hardware?  IF_MAX_VECTORS
should be the value for optimal system behavior.  On top each driver
has its own limitations.  That's how I came to the minimum calculation.

bluhm

> Removing the per-driver constants and just using IF_MAX_VECTORS instead
> sounds more useful to me.
> 
> > 
> > Second part of the diff spreads the interrupts of network devices
> > equally over the softnet tasks.
> > 
> > ok?
> > 
> > bluhm
> > 
> > Index: dev/pci/if_bnxt.c
> > ===================================================================
> > RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_bnxt.c,v
> > diff -u -p -r1.56 if_bnxt.c
> > --- dev/pci/if_bnxt.c	5 Sep 2025 09:58:24 -0000	1.56
> > +++ dev/pci/if_bnxt.c	25 Sep 2025 08:27:45 -0000
> > @@ -545,9 +545,11 @@ bnxt_attach(struct device *parent, struc
> >  		nmsix = pci_intr_msix_count(pa);
> >  		if (nmsix > 1) {
> >  			sc->sc_ih = pci_intr_establish(sc->sc_pc, ih,
> > -			    IPL_NET | IPL_MPSAFE, bnxt_admin_intr, sc, DEVNAME(sc));
> > -			sc->sc_intrmap = intrmap_create(&sc->sc_dev,
> > -			    nmsix - 1, BNXT_MAX_QUEUES, INTRMAP_POWEROF2);
> > +			    IPL_NET | IPL_MPSAFE, bnxt_admin_intr, sc,
> > +			    DEVNAME(sc));
> > +			sc->sc_intrmap = intrmap_create(&sc->sc_dev, nmsix - 1,
> > +			    MIN(BNXT_MAX_QUEUES, IF_MAX_VECTORS),
> > +			    INTRMAP_POWEROF2);
> >  			sc->sc_nqueues = intrmap_count(sc->sc_intrmap);
> >  			KASSERT(sc->sc_nqueues > 0);
> >  			KASSERT(powerof2(sc->sc_nqueues));
> > Index: dev/pci/if_ice.c
> > ===================================================================
> > RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_ice.c,v
> > diff -u -p -r1.59 if_ice.c
> > --- dev/pci/if_ice.c	17 Sep 2025 12:54:19 -0000	1.59
> > +++ dev/pci/if_ice.c	27 Sep 2025 07:35:25 -0000
> > @@ -30501,7 +30501,8 @@ ice_attach_hook(struct device *self)
> >  	sc->sc_nmsix = nmsix;
> >  	nqueues_max = MIN(sc->isc_nrxqsets_max, sc->isc_ntxqsets_max);
> >  	sc->sc_intrmap = intrmap_create(&sc->sc_dev, sc->sc_nmsix - 1,
> > -	    nqueues_max, INTRMAP_POWEROF2);
> > +	    MIN(MIN(nqueues_max, ICE_MAX_VECTORS), IF_MAX_VECTORS),
> > +	    INTRMAP_POWEROF2);
> >  	nqueues = intrmap_count(sc->sc_intrmap);
> >  	KASSERT(nqueues > 0);
> >  	KASSERT(powerof2(nqueues));
> > Index: dev/pci/if_igc.c
> > ===================================================================
> > RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_igc.c,v
> > diff -u -p -r1.28 if_igc.c
> > --- dev/pci/if_igc.c	24 Jun 2025 11:00:27 -0000	1.28
> > +++ dev/pci/if_igc.c	27 Sep 2025 07:29:57 -0000
> > @@ -724,8 +724,8 @@ igc_setup_msix(struct igc_softc *sc)
> >  	/* Give one vector to events. */
> >  	nmsix--;
> >  
> > -	sc->sc_intrmap = intrmap_create(&sc->sc_dev, nmsix, IGC_MAX_VECTORS,
> > -	    INTRMAP_POWEROF2);
> > +	sc->sc_intrmap = intrmap_create(&sc->sc_dev, nmsix,
> > +	    MIN(IGC_MAX_VECTORS, IF_MAX_VECTORS), INTRMAP_POWEROF2);
> >  	sc->sc_nqueues = intrmap_count(sc->sc_intrmap);
> >  }
> >  
> > Index: dev/pci/if_ix.c
> > ===================================================================
> > RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_ix.c,v
> > diff -u -p -r1.221 if_ix.c
> > --- dev/pci/if_ix.c	24 Jun 2025 11:02:03 -0000	1.221
> > +++ dev/pci/if_ix.c	25 Sep 2025 08:27:45 -0000
> > @@ -1854,7 +1854,8 @@ ixgbe_setup_msix(struct ix_softc *sc)
> >  	/* XXX the number of queues is limited to what we can keep stats on */
> >  	maxq = (sc->hw.mac.type == ixgbe_mac_82598EB) ? 8 : 16;
> >  
> > -	sc->sc_intrmap = intrmap_create(&sc->dev, nmsix, maxq, 0);
> > +	sc->sc_intrmap = intrmap_create(&sc->dev, nmsix,
> > +	    MIN(maxq, IF_MAX_VECTORS), 0);
> >  	sc->num_queues = intrmap_count(sc->sc_intrmap);
> >  }
> >  
> > Index: dev/pci/if_ixl.c
> > ===================================================================
> > RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_ixl.c,v
> > diff -u -p -r1.109 if_ixl.c
> > --- dev/pci/if_ixl.c	17 Sep 2025 12:54:19 -0000	1.109
> > +++ dev/pci/if_ixl.c	27 Sep 2025 07:29:57 -0000
> > @@ -1782,8 +1782,9 @@ ixl_attach(struct device *parent, struct
> >  		if (nmsix > 1) { /* we used 1 (the 0th) for the adminq */
> >  			nmsix--;
> >  
> > -			sc->sc_intrmap = intrmap_create(&sc->sc_dev,
> > -			    nmsix, IXL_MAX_VECTORS, INTRMAP_POWEROF2);
> > +			sc->sc_intrmap = intrmap_create(&sc->sc_dev, nmsix,
> > +			    MIN(IXL_MAX_VECTORS, IF_MAX_VECTORS),
> > +			    INTRMAP_POWEROF2);
> >  			nqueues = intrmap_count(sc->sc_intrmap);
> >  			KASSERT(nqueues > 0);
> >  			KASSERT(powerof2(nqueues));
> > Index: net/if.h
> > ===================================================================
> > RCS file: /data/mirror/openbsd/cvs/src/sys/net/if.h,v
> > diff -u -p -r1.221 if.h
> > --- net/if.h	9 Sep 2025 09:16:18 -0000	1.221
> > +++ net/if.h	25 Sep 2025 08:27:45 -0000
> > @@ -526,6 +526,9 @@ struct if_sffpage {
> >  #include <net/if_arp.h>
> >  
> >  #ifdef _KERNEL
> > +
> > +#define IF_MAX_VECTORS		8
> > +
> >  struct socket;
> >  struct ifnet;
> >  struct ifq_ops;
> > Index: net/ifq.c
> > ===================================================================
> > RCS file: /data/mirror/openbsd/cvs/src/sys/net/ifq.c,v
> > diff -u -p -r1.62 ifq.c
> > --- net/ifq.c	28 Jul 2025 05:25:44 -0000	1.62
> > +++ net/ifq.c	25 Sep 2025 08:27:45 -0000
> > @@ -255,7 +255,7 @@ void
> >  ifq_init(struct ifqueue *ifq, struct ifnet *ifp, unsigned int idx)
> >  {
> >  	ifq->ifq_if = ifp;
> > -	ifq->ifq_softnet = net_tq(idx);
> > +	ifq->ifq_softnet = net_tq(ifp->if_index * IF_MAX_VECTORS + idx);
> >  	ifq->ifq_softc = NULL;
> >  
> >  	mtx_init(&ifq->ifq_mtx, IPL_NET);
> >