netdev - Re: [bisected regression] e1000e: "Detected Hardware Unit Hang"

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Date:	Thu, 15 Jan 2015 06:59:13 -0800
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Thomas Jarosch <thomas.jarosch@...ra2net.com>,
	'Linux Netdev List' <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	e1000-devel <e1000-devel@...ts.sourceforge.net>
Subject: Re: [bisected regression] e1000e: "Detected Hardware Unit Hang"

On Thu, 2015-01-15 at 06:43 -0800, Eric Dumazet wrote:
> On Thu, 2015-01-15 at 11:11 +0100, Thomas Jarosch wrote:
> > On Wednesday, 14. January 2015 09:20:52 Eric Dumazet wrote:
> > > I would try to use lower data per txd. I am not sure 24KB is really
> > > supported.
> > > 
> > > ( check commit d821a4c4d11ad160925dab2bb009b8444beff484 for details)
> > > 
> > > diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c
> > > b/drivers/net/ethernet/intel/e1000e/netdev.c index
> > > e14fd85f64eb..8d973f7edfbd 100644
> > > --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> > > +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> > > @@ -3897,7 +3897,7 @@ void e1000e_reset(struct e1000_adapter *adapter)
> > >  	 * limit of 24KB due to receive synchronization limitations.
> > >  	 */
> > >  	adapter->tx_fifo_limit = min_t(u32, ((er32(PBA) >> 16) << 10) - 96,
> > > -				       24 << 10);
> > > +				       8 << 10);
> > > 
> > >  	/* Disable Adaptive Interrupt Moderation if 2 full packets cannot
> > >  	 * fit in receive buffer.
> > 
> > Thanks for checking!
> > 
> > I just tried that change on top of git f800c25 (git HEAD), same problem. 
> > Let's see what the Intel wizards come up with.
> > 
> > What "works" is to decrease the page size in git HEAD, too:
> > 
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index 85ab7d7..9f0ef97 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -2108,7 +2108,7 @@ static inline void __skb_queue_purge(struct 
> > sk_buff_head *list)
> >                 kfree_skb(skb);
> >  }
> >  
> > -#define NETDEV_FRAG_PAGE_MAX_ORDER get_order(32768)
> > +#define NETDEV_FRAG_PAGE_MAX_ORDER get_order(4096)
> >  #define NETDEV_FRAG_PAGE_MAX_SIZE  (PAGE_SIZE << NETDEV_FRAG_PAGE_MAX_ORDER)
> >  #define NETDEV_PAGECNT_MAX_BIAS           NETDEV_FRAG_PAGE_MAX_SIZE
> > 
> > 
> > 
> > When I try a page size of 8192, it starts failing again. I'll now run
> > a stress test with 4096 to see if the problem is really gone
> > or just happens more rarely.
> 
> Sure, you basically reverted my patch.
> 
> You are not the first to report a problem caused by this patch.
> 
> This patch is known to have uncovered some driver bugs.
> 
> We are not going to revert it. We are going to fix the real bugs.
> 
> Thanks
> 
> 

Agreed, we are looking into issue Thomas.

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