linux-kernel - RE: [PATCH 2.6.35-rc6] net-next: Add multiqueue support to vmxnet3 driver

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Date:	Thu, 14 Oct 2010 16:31:35 -0700
From:	Shreyas Bhatewara <sbhatewara@...are.com>
To:	Ben Hutchings <bhutchings@...arflare.com>,
	Stephen Hemminger <shemminger@...tta.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"pv-drivers@...are.com" <pv-drivers@...are.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2.6.35-rc6] net-next: Add multiqueue support to vmxnet3
 driver



> -----Original Message-----
> From: Ben Hutchings [mailto:bhutchings@...arflare.com]
> Sent: Thursday, October 14, 2010 9:31 AM
> To: Stephen Hemminger; Shreyas Bhatewara
> Cc: netdev@...r.kernel.org; pv-drivers@...are.com; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH 2.6.35-rc6] net-next: Add multiqueue support to
> vmxnet3 driver
> 
> On Wed, 2010-10-13 at 14:57 -0700, Stephen Hemminger wrote:
> > On Wed, 13 Oct 2010 14:47:05 -0700 (PDT)
> > Shreyas Bhatewara <sbhatewara@...are.com> wrote:
> >
> > > #ifdef VMXNET3_RSS
> > > +static unsigned int num_rss_entries;
> > > +#define VMXNET3_MAX_DEVICES 10
> > > +
> > > +static int rss_ind_table[VMXNET3_MAX_DEVICES *
> > > +			 VMXNET3_RSS_IND_TABLE_SIZE + 1] = {
> > > +	[0 ... VMXNET3_MAX_DEVICES * VMXNET3_RSS_IND_TABLE_SIZE] = -1 };
> > > +#endif
> > > +static int num_tqs[VMXNET3_MAX_DEVICES + 1] = {
> > > +	[0 ... VMXNET3_MAX_DEVICES] = 1 };
> > > +static int num_rqs[VMXNET3_MAX_DEVICES + 1] = {
> > > +	[0 ... VMXNET3_MAX_DEVICES] = 1 };
> > > +static int share_tx_intr[VMXNET3_MAX_DEVICES + 1] = {
> > > +	[0 ... VMXNET3_MAX_DEVICES] = 0 };
> > > +static int buddy_intr[VMXNET3_MAX_DEVICES + 1] = {
> > > +	[0 ... VMXNET3_MAX_DEVICES] = 1 };
> > > +
> > > +static unsigned int num_adapters;
> > > +module_param_array(share_tx_intr, int, &num_adapters, 0400);
> > > +MODULE_PARM_DESC(share_tx_intr, "Share one IRQ among all tx queue
> completions. "
> > > +		 "Comma separated list of 1s and 0s - one for each NIC. "
> > > +		 "1 to share, 0 to not, default is 0");
> > > +module_param_array(buddy_intr, int, &num_adapters, 0400);
> > > +MODULE_PARM_DESC(buddy_intr, "Share one IRQ among corresponding tx
> and rx "
> > > +		 "queues. Comma separated list of 1s and 0s - one for each
> "
> > > +		 "NIC. 1 to share, 0 to not, default is 1");
> > > +module_param_array(num_tqs, int, &num_adapters, 0400);
> > > +MODULE_PARM_DESC(num_tqs, "Number of transmit queues in each
> adapter. Comma "
> > > +		 "separated list of integers. Setting this to 0 makes
> number"
> > > +		 " of queues same as number of CPUs. Default is 1.");
> > > +
> > > +#ifdef VMXNET3_RSS
> > > +module_param_array(rss_ind_table, int, &num_rss_entries, 0400);
> > > +MODULE_PARM_DESC(rss_ind_table, "RSS Indirection table. Number of
> entries "
> > > +		 "per NIC should be 32. Each integer in a comma separated
> list"
> > > +		 " is an rx queue number starting with 0. Repeat the same
> for"
> > > +		 " all NICs.");
> > > +module_param_array(num_rqs, int, &num_adapters, 0400);
> > > +MODULE_PARM_DESC(num_rqs, "Number of receive queues in each
> adapter. Comma "
> > > +		 " separated list of integers. Setting this to 0 makes
> number"
> > > +		 " of queues same as number of CPUs. Default is 1.");
> >
> > Module parameters are not right for this. They lead to different API
> > for interacting with each driver vendor. Is there a another better
> API?
> > Does it have to be this tweakable in a production environment.
> 
> The ethtool commands ETHTOOL_{G,S}RXFHINDIR cover the RSS indirection
> table.  These are new in 2.6.36 but already supported in the ethtool
> utility.

Thanks Ben,

Good to know. I will try and replace the module parameter for RSS indirection table with handlers for these ethtool commands.


> 
> As for numbers of queues and association of their completions with
> interrupts, we currently have nothing except ETHTOOL_GRXRINGS to get
> the
> number of RX queues.  I did post a tentative definition of an ethtool
> interface for this in
> <http://article.gmane.org/gmane.linux.network/172386> though it
> wouldn't
> provide quite as much control as these module parameters.  It is also
> significantly more difficult to support changing numbers of queues
> after
> an interface has been created, and I have not yet attempted to
> implement
> the 'set' command myself.


Okay. It would be best to keep module parameters to dictate number of queues till ethtool commands to do so become available/easy to use (command to change number of tx queues do not exist).

Regards.
Shreyas


> 
> Ben.
> 
> --
> Ben Hutchings, Senior Software Engineer, Solarflare Communications
> Not speaking for my employer; that's the marketing department's job.
> They asked us to note that Solarflare product names are trademarked.