On Sat, Oct 5, 2013 at 4:12 PM, Alexander V. Chernikov <melif...@freebsd.org > wrote:
> On 05.10.2013 22:07, Bryan Venteicher wrote: > > Author: bryanv > > Date: Sat Oct 5 18:07:24 2013 > > New Revision: 256066 > > URL: http://svnweb.freebsd.org/changeset/base/256066 > > > > Log: > > Do not hold the vtnet Rx queue lock when calling up into the stack > Do you measure performance penalty for this? > > I wasn't able to measure anything, but I don't have the most update hardware either. There should hardly ever be any contention and it should be in its own cacheline, so it is about as cheap as a mutex acquire can get. > > This matches other similar drivers and avoids various LOR warnings. > We're currently trying to eliminate such things in other drivers like > ixgbe, maybe there can be some other way to eliminate possible LORs? > > > Agreed - I'd prefer not to do this and that's why I originally had it commented out. I don't think witness was just reporting a false positives either. vtnet's locking scheme is very similar to ixgbe, so fixes ixgbe should translate to vtnet. > > Approved by: re (marius) > > > > Modified: > > head/sys/dev/virtio/network/if_vtnet.c > > > > Modified: head/sys/dev/virtio/network/if_vtnet.c > > > ============================================================================== > > --- head/sys/dev/virtio/network/if_vtnet.c Sat Oct 5 16:22:33 2013 > (r256065) > > +++ head/sys/dev/virtio/network/if_vtnet.c Sat Oct 5 18:07:24 2013 > (r256066) > > @@ -1700,9 +1700,9 @@ vtnet_rxq_input(struct vtnet_rxq *rxq, s > > rxq->vtnrx_stats.vrxs_ipackets++; > > rxq->vtnrx_stats.vrxs_ibytes += m->m_pkthdr.len; > > > > - /* VTNET_RXQ_UNLOCK(rxq); */ > > + VTNET_RXQ_UNLOCK(rxq); > > (*ifp->if_input)(ifp, m); > > - /* VTNET_RXQ_LOCK(rxq); */ > > + VTNET_RXQ_LOCK(rxq); > > } > > > > static int > > @@ -1782,6 +1782,10 @@ vtnet_rxq_eof(struct vtnet_rxq *rxq) > > m_adj(m, adjsz); > > > > vtnet_rxq_input(rxq, m, hdr); > > + > > + /* Must recheck after dropping the Rx lock. */ > > + if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0) > > + break; > > } > > > > if (deq > 0) > > > > > _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
