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Message-ID: <46E816F5.9010409@intel.com> Date: Wed, 12 Sep 2007 09:42:29 -0700 From: "Kok, Auke" <auke-jan.h.kok@...el.com> To: David Miller <davem@...emloft.net> CC: Robert.Olsson@...a.slu.se, akpm@...ux-foundation.org, jeff@...zik.org, netdev@...r.kernel.org Subject: Re: [PATCH] [-MM, FIX V3] e1000e: incorporate napi_struct changes from net-2.6.24.git David Miller wrote: > From: Robert Olsson <Robert.Olsson@...a.slu.se> > Date: Sat, 8 Sep 2007 09:53:49 +0200 > >> Yes a correct observation. I've spotted this bug too and it caused by the >> policy change in the NAPI scheduling. Look at tx_cleaned. >> >> I suggest we revert this change for now. > > The tx_cleaned logic change was not intentional, and > that's the bug that makes e1000 spin endlessly in NAPI. > > The other part, the work_done < budget part, was intentional > so I'm going to keep it in there for now. I've checked > in the patch below to deal with this. > > I suspect the check "work_done == 0" is some shamans dance > to get slightly better performance, but it's 1) wrong and > 2) at best needs to be explained in a comment and fully > quantified. it probably gives us one more poll, so it might help, this isn't crucial and I agree that it might offset the budgetting. > From e8cbb449155000eecc6e855ea71510fecfc7d5ee Mon Sep 17 00:00:00 2001 > From: David S. Miller <davem@...chee.(none)> > Date: Wed, 12 Sep 2007 16:50:32 +0200 > Subject: [PATCH] [E1000]: Fix unintended NAPI breakout logic change. > > The inversion of the !tx_cleaned test in e1000_clean() > was not intentional, we just wanted to change the > "work_done == 0" to "work_done < budget" > > Noticed by Robert Olsson. > > Signed-off-by: David S. Miller <davem@...emloft.net> > --- > drivers/net/e1000/e1000_main.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c > index 7b0bcdb..58bb758 100644 > --- a/drivers/net/e1000/e1000_main.c > +++ b/drivers/net/e1000/e1000_main.c > @@ -3944,7 +3944,7 @@ e1000_clean(struct napi_struct *napi, int budget) > &work_done, budget); > > /* If no Tx and not enough Rx work done, exit the polling mode */ > - if ((tx_cleaned && (work_done < budget)) || > + if ((!tx_cleaned && (work_done < budget)) || > !netif_running(poll_dev)) { > quit_polling: > if (likely(adapter->itr_setting & 3)) Ack, this is exactly what I did to fix e1000e as well. Auke - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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