svn commit: r205614 - stable/7/sys/dev/msk

[Pyun YongHyeon]

On Tue, Apr 06, 2010 at 08:00:27PM +0200, Andre Albsmeier wrote:
> On Tue, 06-Apr-2010 at 15:46:26 +0200, Andre Albsmeier wrote:
> > On Mon, 05-Apr-2010 at 20:06:42 +0200, Pyun YongHyeon wrote:

[...]

> > > As you know 1.18.2.38 removed taskqueue based interrupt handling so
> > > it could be culprit of the issue. But that revision also removed
> > > two register accesses in TX path so I'd like to know which one
> > > caused the issue. 
> > 
> > I have now tried rev. 1.18.2.38 with this patch (no idea if
> > this is right ;-)):
> > 
> > --- if_msk.c.1.18.2.38	2010-04-06 15:09:19.000000000 +0200
> > +++ if_msk.c.1.18.2.38.TRY	2010-04-06 15:38:13.000000000 +0200
> > @@ -3327,6 +3327,11 @@
> >  	uint32_t control, status;
> >  	int cons, len, port, rxprog;
> >  
> > +	int idx;
> > +	idx = CSR_READ_2(sc, STAT_PUT_IDX);
> > +	if (idx == sc->msk_stat_cons)
> > +		return (0);
> > +
> >  	/* Sync status LEs. */
> >  	bus_dmamap_sync(sc->msk_stat_tag, sc->msk_stat_map,
> >  	    BUS_DMASYNC_POSTREAD | BUS_DMASYNC_POSTWRITE);
> > @@ -3407,7 +3412,7 @@
> >  	if (rxput[MSK_PORT_B] > 0)
> >  		msk_rxput(sc->msk_if[MSK_PORT_B]);
> >  
> > -	return (rxprog > sc->msk_process_limit ? EAGAIN : 0);
> > +	return (sc->msk_stat_cons != CSR_READ_2(sc, STAT_PUT_IDX));
> >  }
> >  
> >  static void
> > 
> > Now performance seems to be the same as with the older
> > driver (at least here at work) and in both directions!
> > Some numbers:
> > 
> > em0 writes to rev. 1.18.2.36:				20 seconds
> > em0 writes to rev. 1.18.2.38:				50 seconds
> > em0 writes to rev. 1.18.2.38 with patch from above:	23 seconds
> > same as before but with int_holdoff: 100 -> 1:		20 seconds
> > 
> > rev. 1.18.2.36 writes to em0:				22 seconds
> > rev. 1.18.2.38 writes to em0:				40 seconds
> > rev. 1.18.2.38 with patch from above writes to em0:	21 seconds
> > same as before but with int_holdoff: 100 -> 1:		20 seconds
> > 
> > It seems that these two CSR_READ_2s really help ;-).
> > 
> > As I said, this is at work and with slightly different machines.
> > I will try things at home later but I am rather confident of
> > receiving good results there as well...
> 
> OK, tests at home show similar good results with the
> above patch. When setting int_holdoff to 3, performance
> seems equal to the older versions.
> 

Thanks a lot for narrowing down the issue.
Because the msk_handle_events() are called in interrupt handler
I'd like to remove the two register accesses in fast path. It seems
accessing STAT_PUT_IDX triggers status updates. Would you try
attached patch and let me know whether the patch makes any
difference?
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