| Message ID | 20121011013420.30383.27700.stgit@jbrandeb-snb.jf.intel.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Jesse Brandeburg <jesse.brandeburg@intel.com> Date: Wed, 10 Oct 2012 18:34:20 -0700 > From: Hiroaki SHIMODA <shimoda.hiroaki@gmail.com> > > This patch originated from Hiroaki SHIMODA but has been modified > by Intel with some minor cleanups and additional commit log text. > > Denys Fedoryshchenko and others reported Tx stalls on e1000e with > BQL enabled. Issue was root caused to hardware delays. They were > introduced because some of the e1000e hardware with transmit > writeback bursting enabled, waits until the driver does an > explict flush OR there are WTHRESH descriptors to write back. > > Sometimes the delays in question were on the order of seconds, > causing visible lag for ssh sessions and unacceptable tx > completion latency, especially for BQL enabled kernels. > > To avoid possible Tx stalls, change WTHRESH back to 1. > > The current plan is to investigate a method for re-enabling > WTHRESH while not harming BQL, but those patches will be later > for net-next if they work. > > please enqueue for stable since v3.3 as this bug was introduced in > commit 3f0cfa3bc11e7f00c9994e0f469cbc0e7da7b00c > Author: Tom Herbert <therbert@google.com> > Date: Mon Nov 28 16:33:16 2011 +0000 > > e1000e: Support for byte queue limits > > Changes to e1000e to use byte queue limits. > > Reported-by: Denys Fedoryshchenko <denys@visp.net.lb> > Tested-by: Denys Fedoryshchenko <denys@visp.net.lb> > Signed-off-by: Hiroaki SHIMODA <shimoda.hiroaki@gmail.com> > CC: eric.dumazet@gmail.com > CC: therbert@google.com > Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com> Applied and queued up for -stable, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/ethernet/intel/e1000e/e1000.h b/drivers/net/ethernet/intel/e1000e/e1000.h index cb3356c..04668b4 100644 --- a/drivers/net/ethernet/intel/e1000e/e1000.h +++ b/drivers/net/ethernet/intel/e1000e/e1000.h @@ -175,13 +175,13 @@ struct e1000_info; /* * in the case of WTHRESH, it appears at least the 82571/2 hardware * writes back 4 descriptors when WTHRESH=5, and 3 descriptors when - * WTHRESH=4, and since we want 64 bytes at a time written back, set - * it to 5 + * WTHRESH=4, so a setting of 5 gives the most efficient bus + * utilization but to avoid possible Tx stalls, set it to 1 */ #define E1000_TXDCTL_DMA_BURST_ENABLE \ (E1000_TXDCTL_GRAN | /* set descriptor granularity */ \ E1000_TXDCTL_COUNT_DESC | \ - (5 << 16) | /* wthresh must be +1 more than desired */\ + (1 << 16) | /* wthresh must be +1 more than desired */\ (1 << 8) | /* hthresh */ \ 0x1f) /* pthresh */ diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c index de57a2b..f444eb0 100644 --- a/drivers/net/ethernet/intel/e1000e/netdev.c +++ b/drivers/net/ethernet/intel/e1000e/netdev.c @@ -2831,7 +2831,7 @@ static void e1000_configure_tx(struct e1000_adapter *adapter) * set up some performance related parameters to encourage the * hardware to use the bus more efficiently in bursts, depends * on the tx_int_delay to be enabled, - * wthresh = 5 ==> burst write a cacheline (64 bytes) at a time + * wthresh = 1 ==> burst write is disabled to avoid Tx stalls * hthresh = 1 ==> prefetch when one or more available * pthresh = 0x1f ==> prefetch if internal cache 31 or less * BEWARE: this seems to work but should be considered first if