DPDK patches and discussions
 help / color / mirror / Atom feed
From: Neil Horman <nhorman@tuxdriver.com>
To: "Richardson, Bruce" <bruce.richardson@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 3/5] testpmd: Change rxfreet default to 32
Date: Thu, 18 Sep 2014 14:03:36 -0400
Message-ID: <20140918180336.GM20389@hmsreliant.think-freely.org> (raw)
In-Reply-To: <59AF69C657FD0841A61C55336867B5B0343F355F@IRSMSX103.ger.corp.intel.com>

On Thu, Sep 18, 2014 at 03:53:33PM +0000, Richardson, Bruce wrote:
> > -----Original Message-----
> > From: Neil Horman [mailto:nhorman@tuxdriver.com]
> > Sent: Wednesday, September 17, 2014 4:30 PM
> > To: Richardson, Bruce
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH 3/5] testpmd: Change rxfreet default to 32
> > 
> > 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 <bruce.richardson@intel.com>
> > > ---
> > >  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 = {
> > >  /*
> > >   * 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
> > */
> > >
> > 
> > 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 tuned driver, but it works fine for all other ones too, as far as I'm aware. Basically, this 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. 
> 

Maybe codify that information as a macro, or with some documentation right above
the setting, so people not using ixgbe don't have to wonder where that value
came from? :)

Neil

> /Bruce
> 
> 

  parent reply	other threads:[~2014-09-18 17:57 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-17 10:01 [dpdk-dev] [PATCH 0/5] Mbuf Structure Rework, part 3 Bruce Richardson
2014-09-17 10:01 ` [dpdk-dev] [PATCH 1/5] mbuf: ensure next pointer is set to null on free Bruce Richardson
2014-09-17 10:01 ` [dpdk-dev] [PATCH 2/5] ixgbe: add prefetch to improve slow-path tx perf Bruce Richardson
2014-09-17 15:21   ` Neil Horman
2014-09-17 15:35     ` Richardson, Bruce
2014-09-17 17:59       ` Neil Horman
2014-09-18 13:36         ` Bruce Richardson
2014-09-18 15:29           ` Neil Horman
2014-09-18 15:42             ` Bruce Richardson
2014-09-18 17:56               ` Neil Horman
2014-09-17 10:01 ` [dpdk-dev] [PATCH 3/5] testpmd: Change rxfreet default to 32 Bruce Richardson
2014-09-17 15:29   ` Neil Horman
2014-09-18 15:53     ` Richardson, Bruce
2014-09-18 17:13       ` Thomas Monjalon
2014-09-18 18:08         ` Neil Horman
2014-09-19  9:18           ` Richardson, Bruce
2014-09-19 10:24             ` Neil Horman
2014-09-19 10:28               ` Richardson, Bruce
2014-09-19 15:18                 ` Neil Horman
2014-09-18 18:03       ` Neil Horman [this message]
2014-09-17 10:01 ` [dpdk-dev] [PATCH 4/5] mbuf: add userdata pointer field Bruce Richardson
2014-09-17 15:35   ` Neil Horman
2014-09-17 16:02     ` Richardson, Bruce
2014-09-17 18:29       ` Neil Horman
2014-09-17 10:01 ` [dpdk-dev] [PATCH 5/5] mbuf: Add in second vlan tag field to mbuf Bruce Richardson
2014-09-17 20:46   ` Stephen Hemminger
2014-09-23 11:08 ` [dpdk-dev] [PATCH v2 0/5] Mbuf Structure Rework, part 3 Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 1/5] mbuf: ensure next pointer is set to null on free Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 2/5] ixgbe: add prefetch to improve slow-path tx perf Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 3/5] testpmd: Change rxfreet default to 32 Bruce Richardson
2014-09-23 17:02     ` Neil Horman
2014-09-24  9:03       ` Richardson, Bruce
2014-09-24 10:05         ` Neil Horman
2014-11-07 12:30         ` Thomas Monjalon
2014-11-07 13:49           ` Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 4/5] mbuf: add userdata pointer field Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 5/5] mbuf: switch vlan_tci and reserved2 fields Bruce Richardson
2014-09-29 15:58   ` [dpdk-dev] [PATCH v2 0/5] Mbuf Structure Rework, part 3 De Lara Guarch, Pablo
2014-10-08 12:31     ` Thomas Monjalon

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20140918180336.GM20389@hmsreliant.think-freely.org \
    --to=nhorman@tuxdriver.com \
    --cc=bruce.richardson@intel.com \
    --cc=dev@dpdk.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

DPDK patches and discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/dev/0 dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dev dev/ https://inbox.dpdk.org/dev \
		dev@dpdk.org
	public-inbox-index dev

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git