netdev - Re: [PATCH 1/2] ixgbe, make interrupt allocations NUMA aware

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Date:	Mon, 24 Feb 2014 14:39:58 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
CC:	netdev@...r.kernel.org, Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Carolyn Wyborny <carolyn.wyborny@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	Greg Rose <gregory.v.rose@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	Mitch Williams <mitch.a.williams@...el.com>,
	"David S. Miller" <davem@...emloft.net>, nhorman@...hat.com,
	agospoda@...hat.com, e1000-devel@...ts.sourceforge.net
Subject: Re: [PATCH 1/2] ixgbe, make interrupt allocations NUMA aware



On 02/24/2014 02:26 PM, Alexander Duyck wrote:
> On 02/24/2014 10:51 AM, Prarit Bhargava wrote:
>> The ixgbe driver creates one queue/cpu on the system in order to spread
>> work out on all cpus rather than restricting work to a single cpu.  This
>> model, while efficient, does not take into account the NUMA configuration
>> of the system.
>>
>> This patch introduces ixgbe_num_cpus() which returns
>> the number of online cpus if the adapter's PCI device has no NUMA
>> restrictions, and the number of cpus in the node if the PCI device is
>> allocated to a specific node.
>>
>> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
>> Cc: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
>> Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>
>> Cc: Bruce Allan <bruce.w.allan@...el.com>
>> Cc: Carolyn Wyborny <carolyn.wyborny@...el.com>
>> Cc: Don Skidmore <donald.c.skidmore@...el.com>
>> Cc: Greg Rose <gregory.v.rose@...el.com>
>> Cc: Alex Duyck <alexander.h.duyck@...el.com>
>> Cc: John Ronciak <john.ronciak@...el.com>
>> Cc: Mitch Williams <mitch.a.williams@...el.com>
>> Cc: "David S. Miller" <davem@...emloft.net>
>> Cc: nhorman@...hat.com
>> Cc: agospoda@...hat.com
>> Cc: e1000-devel@...ts.sourceforge.net
>> ---
>>  drivers/net/ethernet/intel/ixgbe/ixgbe.h       |    2 ++
>>  drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c   |   28 +++++++++++++++++++++---
>>  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c  |    6 ++---
>>  drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c |    5 +++--
>>  4 files changed, 33 insertions(+), 8 deletions(-)
>>
> 
> [...]
> 
>> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
>> index 18076c4..b68a6e9 100644
>> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
>> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
>> @@ -4953,13 +4953,13 @@ static int ixgbe_sw_init(struct ixgbe_adapter *adapter)
>>  	hw->subsystem_device_id = pdev->subsystem_device;
>>  
>>  	/* Set common capability flags and settings */
>> -	rss = min_t(int, IXGBE_MAX_RSS_INDICES, num_online_cpus());
>> +	rss = min_t(int, IXGBE_MAX_RSS_INDICES, ixgbe_num_cpus(adapter));
>>  	adapter->ring_feature[RING_F_RSS].limit = rss;
>>  	adapter->flags2 |= IXGBE_FLAG2_RSC_CAPABLE;
>>  	adapter->flags2 |= IXGBE_FLAG2_RSC_ENABLED;
>>  	adapter->max_q_vectors = MAX_Q_VECTORS_82599;
>>  	adapter->atr_sample_rate = 20;
>> -	fdir = min_t(int, IXGBE_MAX_FDIR_INDICES, num_online_cpus());
>> +	fdir = min_t(int, IXGBE_MAX_FDIR_INDICES, ixgbe_num_cpus(adapter));
>>  	adapter->ring_feature[RING_F_FDIR].limit = fdir;
>>  	adapter->fdir_pballoc = IXGBE_FDIR_PBALLOC_64K;
>>  #ifdef CONFIG_IXGBE_DCA
> 
> This is the one bit I object to in this patch.  The flow director queue
> count should be equal to the number of online CPUs, or at least as close
> to it as the hardware can get.  Otherwise ATR is completely useless.

I'm reading up on ATR now and I see your point completely.  I will remove this
chunk in V2.  OOC, however, what about my concern with ATR & the location of the
PCI device (on a different root bridge)?  Isn't that a concern with ATR or am I
missing something with the overall scheme of ATR?

P.

> 
> Thanks,
> 
> Alex
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