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From:
Jan Klemkow <jan@openbsd.org>
Subject:
Re: reduce redundant load_mbuf code
To:
tech@openbsd.org
Date:
Tue, 12 Aug 2025 20:55:00 +0200

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On Tue, Aug 12, 2025 at 08:42:36PM +0200, Claudio Jeker wrote:
> On Tue, Aug 12, 2025 at 08:39:02PM +0200, Jan Klemkow wrote:
> > Hi,
> > 
> > This diff reduces the redundant bus_dmamap_load_mbuf(), m_defrag() and
> > bus_dmamap_load_mbuf() call chain.  In many other interface drivers are
> > similar implementations with switch/case statements, which could be
> > reduced with the same function but in a separate diff.
> > 
> > ok?
> 
> Please don't do that. The goal is to put m_defrag into
> bus_dmamap_load_mbuf() and not hide it behind yet another abstraction.

I tried you suggestion first, but bus_dmamap_load_mbuf() is very
different between the architectures.  I could try in small steps, arch
by arch?!  For instance compare amd64 and sparc64.  I couldn't get why
bus_dmamap_load_mbuf() in sparc64 don't just use bus_dmamap_load_buffer().

Thanks,
Jan

> > Index: dev/pci/if_iavf.c
> > ===================================================================
> > RCS file: /cvs/src/sys/dev/pci/if_iavf.c,v
> > diff -u -p -r1.25 if_iavf.c
> > --- dev/pci/if_iavf.c	24 Jun 2025 10:59:15 -0000	1.25
> > +++ dev/pci/if_iavf.c	12 Aug 2025 17:30:35 -0000
> > @@ -1915,24 +1915,6 @@ iavf_txr_free(struct iavf_softc *sc, str
> >  	free(txr, M_DEVBUF, sizeof(*txr));
> >  }
> >  
> > -static inline int
> > -iavf_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m)
> > -{
> > -	int error;
> > -
> > -	error = bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT);
> > -	if (error != EFBIG)
> > -		return (error);
> > -
> > -	error = m_defrag(m, M_DONTWAIT);
> > -	if (error != 0)
> > -		return (error);
> > -
> > -	return (bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT));
> > -}
> > -
> >  static uint64_t
> >  iavf_tx_offload(struct mbuf *m, struct iavf_tx_ring *txr, unsigned int prod)
> >  {
> > @@ -2072,7 +2054,7 @@ iavf_start(struct ifqueue *ifq)
> >  			free--;
> >  		}
> >  
> > -		if (iavf_load_mbuf(sc->sc_dmat, map, m) != 0) {
> > +		if (m_load_dmamap(sc->sc_dmat, map, m) != 0) {
> >  			ifq->ifq_errors++;
> >  			m_freem(m);
> >  			continue;
> > Index: dev/pci/if_ice.c
> > ===================================================================
> > RCS file: /cvs/src/sys/dev/pci/if_ice.c,v
> > diff -u -p -r1.56 if_ice.c
> > --- dev/pci/if_ice.c	17 Jul 2025 09:19:21 -0000	1.56
> > +++ dev/pci/if_ice.c	12 Aug 2025 17:07:02 -0000
> > @@ -13791,24 +13791,6 @@ ice_tx_setup_offload(struct mbuf *m0, st
> >  	return offload;
> >  }
> >  
> > -static inline int
> > -ice_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m)
> > -{
> > -	int error;
> > -
> > -	error = bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT);
> > -	if (error != EFBIG)
> > -		return (error);
> > -
> > -	error = m_defrag(m, M_DONTWAIT);
> > -	if (error != 0)
> > -		return (error);
> > -
> > -	return (bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT));
> > -}
> > -
> >  void
> >  ice_set_tso_context(struct mbuf *m0, struct ice_tx_queue *txq,
> >      unsigned int prod, struct ether_extracted *ext)
> > @@ -13905,7 +13887,7 @@ ice_start(struct ifqueue *ifq)
> >  		txm = &txq->tx_map[prod];
> >  		map = txm->txm_map;
> >  
> > -		if (ice_load_mbuf(sc->sc_dmat, map, m) != 0) {
> > +		if (m_load_dmamap(sc->sc_dmat, map, m) != 0) {
> >  			ifq->ifq_errors++;
> >  			m_freem(m);
> >  			continue;
> > Index: dev/pci/if_igc.c
> > ===================================================================
> > RCS file: /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	12 Aug 2025 17:08:18 -0000
> > @@ -937,24 +937,6 @@ igc_init(void *arg)
> >  	splx(s);
> >  }
> >  
> > -static inline int
> > -igc_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m)
> > -{
> > -	int error;
> > -
> > -	error = bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT);
> > -	if (error != EFBIG)
> > -		return (error);
> > -
> > -	error = m_defrag(m, M_DONTWAIT);
> > -	if (error != 0)
> > -		return (error);
> > -
> > -	return (bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT));
> > -}
> > -
> >  void
> >  igc_start(struct ifqueue *ifq)
> >  {
> > @@ -1003,7 +985,7 @@ igc_start(struct ifqueue *ifq)
> >  		txbuf = &txr->tx_buffers[prod];
> >  		map = txbuf->map;
> >  
> > -		if (igc_load_mbuf(txr->txdma.dma_tag, map, m) != 0) {
> > +		if (m_load_dmamap(txr->txdma.dma_tag, map, m) != 0) {
> >  			ifq->ifq_errors++;
> >  			m_freem(m);
> >  			continue;
> > Index: dev/pci/if_ixl.c
> > ===================================================================
> > RCS file: /cvs/src/sys/dev/pci/if_ixl.c,v
> > diff -u -p -r1.108 if_ixl.c
> > --- dev/pci/if_ixl.c	24 Jun 2025 11:03:10 -0000	1.108
> > +++ dev/pci/if_ixl.c	12 Aug 2025 17:06:16 -0000
> > @@ -2746,24 +2746,6 @@ ixl_txr_free(struct ixl_softc *sc, struc
> >  	free(txr, M_DEVBUF, sizeof(*txr));
> >  }
> >  
> > -static inline int
> > -ixl_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m)
> > -{
> > -	int error;
> > -
> > -	error = bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT);
> > -	if (error != EFBIG)
> > -		return (error);
> > -
> > -	error = m_defrag(m, M_DONTWAIT);
> > -	if (error != 0)
> > -		return (error);
> > -
> > -	return (bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT));
> > -}
> > -
> >  static uint64_t
> >  ixl_tx_setup_offload(struct mbuf *m0, struct ixl_tx_ring *txr,
> >      unsigned int prod)
> > @@ -2905,7 +2887,7 @@ ixl_start(struct ifqueue *ifq)
> >  			free--;
> >  		}
> >  
> > -		if (ixl_load_mbuf(sc->sc_dmat, map, m) != 0) {
> > +		if (m_load_dmamap(sc->sc_dmat, map, m) != 0) {
> >  			ifq->ifq_errors++;
> >  			m_freem(m);
> >  			continue;
> > Index: dev/pci/if_vmx.c
> > ===================================================================
> > RCS file: /cvs/src/sys/dev/pci/if_vmx.c,v
> > diff -u -p -r1.93 if_vmx.c
> > --- dev/pci/if_vmx.c	19 Jun 2025 09:36:21 -0000	1.93
> > +++ dev/pci/if_vmx.c	12 Aug 2025 17:07:26 -0000
> > @@ -1535,24 +1535,6 @@ vmxnet3_ioctl(struct ifnet *ifp, u_long 
> >  	return error;
> >  }
> >  
> > -static inline int
> > -vmx_load_mbuf(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m)
> > -{
> > -	int error;
> > -
> > -	error = bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT);
> > -	if (error != EFBIG)
> > -		return (error);
> > -
> > -	error = m_defrag(m, M_DONTWAIT);
> > -	if (error != 0)
> > -		return (error);
> > -
> > -	return (bus_dmamap_load_mbuf(dmat, map, m,
> > -	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT));
> > -}
> > -
> >  void
> >  vmxnet3_tx_offload(struct vmxnet3_txdesc *sop, struct mbuf *m)
> >  {
> > @@ -1695,7 +1677,7 @@ vmxnet3_start(struct ifqueue *ifq)
> >  
> >  		map = ring->dmap[prod];
> >  
> > -		if (vmx_load_mbuf(sc->sc_dmat, map, m) != 0) {
> > +		if (m_load_dmamap(sc->sc_dmat, map, m) != 0) {
> >  			ifq->ifq_errors++;
> >  			m_freem(m);
> >  			continue;
> > Index: sys/mbuf.h
> > ===================================================================
> > RCS file: /cvs/src/sys/sys/mbuf.h,v
> > diff -u -p -r1.267 mbuf.h
> > --- sys/mbuf.h	25 Jun 2025 20:26:32 -0000	1.267
> > +++ sys/mbuf.h	12 Aug 2025 17:10:52 -0000
> > @@ -35,6 +35,7 @@
> >  #ifndef _SYS_MBUF_H_
> >  #define _SYS_MBUF_H_
> >  
> > +#include <machine/bus.h>
> >  #include <sys/queue.h>
> >  
> >  /*
> > @@ -464,6 +465,24 @@ m_freemp(struct mbuf **mp)
> >  
> >  	*mp = NULL;
> >  	return m_freem(m);
> > +}
> > +
> > +static inline int
> > +m_load_dmamap(bus_dma_tag_t dmat, bus_dmamap_t map, struct mbuf *m)
> > +{
> > +	int error;
> > +
> > +	error = bus_dmamap_load_mbuf(dmat, map, m,
> > +	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT);
> > +	if (error != EFBIG)
> > +		return (error);
> > +
> > +	error = m_defrag(m, M_DONTWAIT);
> > +	if (error != 0)
> > +		return (error);
> > +
> > +	return (bus_dmamap_load_mbuf(dmat, map, m,
> > +	    BUS_DMA_STREAMING | BUS_DMA_NOWAIT));
> >  }
> >  
> >  #include <sys/percpu.h>
> > 
> 
> -- 
> :wq Claudio
>