From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Richardson, Bruce" Subject: Re: [PATCH 3/5] testpmd: Change rxfreet default to 32 Date: Thu, 18 Sep 2014 15:53:33 +0000 Message-ID: <59AF69C657FD0841A61C55336867B5B0343F355F@IRSMSX103.ger.corp.intel.com> References: <1410948102-12740-1-git-send-email-bruce.richardson@intel.com> <1410948102-12740-4-git-send-email-bruce.richardson@intel.com> <20140917152945.GF4213@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Cc: "dev-VfR2kkLFssw@public.gmane.org" To: Neil Horman Return-path: In-Reply-To: <20140917152945.GF4213-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org> Content-Language: en-US List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" > -----Original Message----- > From: Neil Horman [mailto:nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org] > Sent: Wednesday, September 17, 2014 4:30 PM > To: Richardson, Bruce > Cc: dev-VfR2kkLFssw@public.gmane.org > Subject: Re: [dpdk-dev] [PATCH 3/5] testpmd: Change rxfreet default to 32 >=20 > On Wed, Sep 17, 2014 at 11:01:40AM +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. > > > > Signed-off-by: Bruce Richardson > > --- > > app/test-pmd/testpmd.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c > > index 9f6cdc4..5751607 100644 > > --- a/app/test-pmd/testpmd.c > > +++ b/app/test-pmd/testpmd.c > > @@ -225,7 +225,7 @@ struct rte_eth_thresh tx_thresh =3D { > > /* > > * Configurable value of RX free threshold. > > */ > > -uint16_t rx_free_thresh =3D 0; /* Immediately free RX descriptors by d= efault. */ > > +uint16_t rx_free_thresh =3D 32; /* Refill RX descriptors once every 32= packets > */ > > >=20 > Why 32? Was that an experimentally determined value? Does it hold true = for all > PMD's? This is primarily for the ixgbe PMD, which is right now the most highly tun= ed driver, but it works fine for all other ones too, as far as I'm aware. B= asically, this is the minimum setting needed to enable either the bulk allo= c or vector RX routines inside the ixgbe driver, so it's best made the defa= ult 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.=20 /Bruce