On Wed, Sep 24, 2014 at 09:03:20AM +0000, Richardson, Bruce wrote: > > -----Original Message----- > > From: Neil Horman [mailto:nhorman at tuxdriver.com] > > Sent: Tuesday, September 23, 2014 6:03 PM > > To: Richardson, Bruce > > Cc: dev at dpdk.org > > Subject: Re: [dpdk-dev] [PATCH v2 3/5] testpmd: Change rxfreet default to 32 > > > > On Tue, Sep 23, 2014 at 12:08:15PM +0100, Bruce Richardson wrote: > > > To improve performance by using bulk alloc or vectored RX routines, we > > > need to set rx free threshold (rxfreet) value to 32, so make this the > > > testpmd default. > > > > > > Thirty-two is the minimum setting needed to enable either the > > > bulk alloc or vector RX routines inside the ixgbe driver, so it's > > > best made the default for that reason. Please see > > > "check_rx_burst_bulk_alloc_preconditions()" in ixgbe_rxtx.c, and > > > RX function assignment logic in "ixgbe_dev_rx_queue_setup()" in > > > the same file. > > > > > > The difference in IO performance for testpmd when called without any > > > optional parameters, and using 10G NICs using the ixgbe driver, can be > > > significant - approx 25% or more. > > > > > > Updates in V2: > > > * Updated commit message with additional details > > > > > > Signed-off-by: Bruce Richardson <bruce.richardson at intel.com> > > > --- > > > app/test-pmd/testpmd.c | 4 +++- > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c > > > index 9f6cdc4..f76406f 100644 > > > --- a/app/test-pmd/testpmd.c > > > +++ b/app/test-pmd/testpmd.c > > > @@ -225,7 +225,9 @@ struct rte_eth_thresh tx_thresh = { > > > /* > > > * Configurable value of RX free threshold. > > > */ > > > -uint16_t rx_free_thresh = 0; /* Immediately free RX descriptors by > > > default. */ > > > +uint16_t rx_free_thresh = 32; /* Refill RX descriptors once every 32 > > > packets, > > > + This setting is needed for ixgbe to enable bulk alloc or vector > > > + receive functionality. */ > > > > I thought we were talking about making this a pmd private selectable item, > > or > > allowing a reserved "let the pmd decide" setting. Or are we saving that > > for a > > later time? > > > > Yes, we are looking at that - and hopefully we can also get a patch for that > in for our next release. However, I've left this patch in just in case that > doesn't actually happen, as the performance improvements for 10G are just too > good to leave aside for the sake of a 1-line change. Ideally, I'd like this > go to in, and then be replaced by a "proper" fix. > Ok, thanks Neil
> /Bruce > > > Neil > > > > > > > > /* > > > * Configurable value of RX drop enable. > > > -- > > > 1.9.3 > > > > > > >
