ixgbe rx & tx locks

[John Baldwin]

On Thursday, August 16, 2012 5:40:35 pm Jack Vogel wrote:
> Thanks John, am seeing this, just busy on another matter, will get to it
> asap.

Vijay, can you test this to see if it helps with your test case?

> Jack
> 
> 
> On Thu, Aug 16, 2012 at 2:36 PM, John Baldwin <jhb at freebsd.org> wrote:
> 
> > On Thursday, August 16, 2012 8:35:53 am John Baldwin wrote:
> > > On Monday, August 13, 2012 6:17:53 pm Jack Vogel wrote:
> > > > After looking at the code again I think this is just what's happening,
> > > > mq_start
> > > > will schedule the task when it can't get the lock (due to the 
interrupt
> > > > already
> > > > holding it presumeably), so you get the tasklet code in contention
> > with the
> > > > interrupt.
> > > >
> > > > Anyone with a clever notion of how to do things better?
> > >
> > > Are you queueing a task that does both RX and TX?  That was a bug I 
fixed
> > > in igb that caused out-of-order packet processing for RX with igb.  igb
> > > uses a smaller task for when it's start routine fails that only tries to
> > > restart transmission but doesn't do fullblown interrupt handling.
> > >
> > > Here's a possible patch (compiles, not run-tested) to implement this for
> > > ixgbe:
> > >
> > > http://www.FreeBSD.org/~jhb/patches/ixgbe_txq_task.patch
> >
> > Actually, it looks like recent changes to the watchdog handling have
> > reintroduced a variant of this bug.  They schedule the full RX/TX task
> > to run anytime the timer fires and there are pending TX completions
> > that are in progress.  This seems a bit odd as in the normal case you
> > will get a TX completion interrupt once there is something to do.  OTOH,
> > it adds another instance of duplicate RX processing which is much worse
> > than what this is trying to fix.  I've updated this patch to disable
> > that bit of the watchdog handler in both igb and ixgbe:
> >
> > http://www.FreeBSD.org/~jhb/patches/ixgbe_txq_task2.patch
> >
> > --
> > John Baldwin
> >
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-- 
John Baldwin