[V4,net-next] net: mana: Assigning IRQ affinity on HT cores

  Existing MANA design assigns IRQ to every CPU, including sibling
hyper-threads. This may cause multiple IRQs to be active simultaneously
in the same core and may reduce the network performance with RSS.

Improve the performance by assigning IRQ to non sibling CPUs in local
NUMA node.

Signed-off-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
---
V3 -> V4:
* Used for_each_numa_hop_mask() macro and simplified the code.
Thanks to Yury Norov for the suggestion.
* Added code to assign hwc irq separately in mana_gd_setup_irqs.

V2 -> V3:
* Created a helper function to get the next NUMA with CPU.
* Added some error checks for unsuccessful memory allocation.
* Fixed some comments on the code.

V1 -> V2:
* Simplified the code by removing filter_mask_list and using avail_cpus.
* Addressed infinite loop issue when there are numa nodes with no CPUs.
* Addressed uses of local numa node instead of 0 to start.
* Removed uses of BUG_ON.
* Placed cpus_read_lock in parent function to avoid num_online_cpus
  to get changed before function finishes the affinity assignment.
---
 .../net/ethernet/microsoft/mana/gdma_main.c   | 70 +++++++++++++++++--
 1 file changed, 63 insertions(+), 7 deletions(-)
  

On Mon, Dec 04, 2023 at 12:50:41AM -0800, Souradeep Chakrabarti wrote:
> Existing MANA design assigns IRQ to every CPU, including sibling
> hyper-threads. This may cause multiple IRQs to be active simultaneously
> in the same core and may reduce the network performance with RSS.
> 
> Improve the performance by assigning IRQ to non sibling CPUs in local
> NUMA node.
> 
> Signed-off-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
> ---
> V3 -> V4:
> * Used for_each_numa_hop_mask() macro and simplified the code.
> Thanks to Yury Norov for the suggestion.

We've got a special tag for this:

Suggested-by: Yury Norov <yury.norov@gmali.com>

> * Added code to assign hwc irq separately in mana_gd_setup_irqs.
> 
> V2 -> V3:
> * Created a helper function to get the next NUMA with CPU.
> * Added some error checks for unsuccessful memory allocation.
> * Fixed some comments on the code.
> 
> V1 -> V2:
> * Simplified the code by removing filter_mask_list and using avail_cpus.
> * Addressed infinite loop issue when there are numa nodes with no CPUs.
> * Addressed uses of local numa node instead of 0 to start.
> * Removed uses of BUG_ON.
> * Placed cpus_read_lock in parent function to avoid num_online_cpus
>   to get changed before function finishes the affinity assignment.
> ---
>  .../net/ethernet/microsoft/mana/gdma_main.c   | 70 +++++++++++++++++--
>  1 file changed, 63 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> index 6367de0c2c2e..2194a53cce10 100644
> --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> @@ -1243,15 +1243,57 @@ void mana_gd_free_res_map(struct gdma_resource *r)
>  	r->size = 0;
>  }
>  
> +static int irq_setup(int *irqs, int nvec, int start_numa_node)
> +{
> +	int i = 0, cpu, err = 0;
> +	const struct cpumask *node_cpumask;
> +	unsigned int  next_node = start_numa_node;
> +	cpumask_var_t visited_cpus, node_cpumask_temp;
> +
> +	if (!zalloc_cpumask_var(&visited_cpus, GFP_KERNEL)) {
> +		err = ENOMEM;
> +		return err;
> +	}
> +	if (!zalloc_cpumask_var(&node_cpumask_temp, GFP_KERNEL)) {
> +		err = -ENOMEM;
> +		return err;
> +	}

Can you add a bit more of vertical spacing?

> +	rcu_read_lock();
> +	for_each_numa_hop_mask(node_cpumask, next_node) {
> +		cpumask_copy(node_cpumask_temp, node_cpumask);
> +		for_each_cpu(cpu, node_cpumask_temp) {
> +			cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> +				       topology_sibling_cpumask(cpu));
> +			irq_set_affinity_and_hint(irqs[i], cpumask_of(cpu));
> +			if (++i == nvec)
> +				goto free_mask;
> +			cpumask_set_cpu(cpu, visited_cpus);
> +			if (cpumask_empty(node_cpumask_temp)) {
> +				cpumask_copy(node_cpumask_temp, node_cpumask);
> +				cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> +					       visited_cpus);
> +				cpu = 0;
> +			}

It feels like you can calculate number of sibling groups in a hop in
advance, so that you'll know how many IRQs you want to assign per each
hop, and avoid resetting the node_cpumask_temp and spinning in inner
loop for more than once...

Can you print your topology, and describe how you want to spread IRQs
on it, and how your existing code does spread them?

Please add performance results in the commit message.

I feel like this may be a useful code for other kernel folks, and if
so, we'd invest in it for more and make it a generic API, similar to
cpumaks_local_spread()...

> +		}
> +	}
> +free_mask:
> +	rcu_read_unlock();
> +	free_cpumask_var(visited_cpus);
> +	free_cpumask_var(node_cpumask_temp);
> +	return err;
> +}
> +
>  static int mana_gd_setup_irqs(struct pci_dev *pdev)
>  {
> -	unsigned int max_queues_per_port = num_online_cpus();
>  	struct gdma_context *gc = pci_get_drvdata(pdev);
> +	unsigned int max_queues_per_port;
>  	struct gdma_irq_context *gic;
>  	unsigned int max_irqs, cpu;
> -	int nvec, irq;
> +	int nvec, *irqs, irq;
>  	int err, i = 0, j;
>  
> +	cpus_read_lock();
> +	max_queues_per_port = num_online_cpus();
>  	if (max_queues_per_port > MANA_MAX_NUM_QUEUES)
>  		max_queues_per_port = MANA_MAX_NUM_QUEUES;
>  
> @@ -1261,6 +1303,11 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
>  	nvec = pci_alloc_irq_vectors(pdev, 2, max_irqs, PCI_IRQ_MSIX);
>  	if (nvec < 0)
>  		return nvec;
> +	irqs = kmalloc_array(max_queues_per_port, sizeof(int), GFP_KERNEL);
> +	if (!irqs) {
> +		err = -ENOMEM;
> +		goto free_irq_vector;
> +	}
>  
>  	gc->irq_contexts = kcalloc(nvec, sizeof(struct gdma_irq_context),
>  				   GFP_KERNEL);
> @@ -1287,21 +1334,28 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
>  			goto free_irq;
>  		}
>  
> -		err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
> +		if (!i) {
> +			err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
> +			cpu = cpumask_local_spread(i, gc->numa_node);

If i == 0, you can simplify it because you just need the 1st CPU from
a given node.

> +			irq_set_affinity_and_hint(irq, cpumask_of(cpu));
> +		} else {
> +			irqs[i - 1] = irq;
> +			err = request_irq(irqs[i - 1], mana_gd_intr, 0, gic->name, gic);
> +		}
>  		if (err)
>  			goto free_irq;
> -
> -		cpu = cpumask_local_spread(i, gc->numa_node);
> -		irq_set_affinity_and_hint(irq, cpumask_of(cpu));
>  	}
>  
> +	err = irq_setup(irqs, max_queues_per_port, gc->numa_node);
> +	if (err)
> +		goto free_irq;
>  	err = mana_gd_alloc_res_map(nvec, &gc->msix_resource);
>  	if (err)
>  		goto free_irq;
>  
>  	gc->max_num_msix = nvec;
>  	gc->num_msix_usable = nvec;
> -
> +	cpus_read_unlock();
>  	return 0;
>  
>  free_irq:
> @@ -1314,8 +1368,10 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
>  	}
>  
>  	kfree(gc->irq_contexts);
> +	kfree(irqs);
>  	gc->irq_contexts = NULL;
>  free_irq_vector:
> +	cpus_read_unlock();
>  	pci_free_irq_vectors(pdev);
>  	return err;
>  }
> -- 
> 2.34.1
  

On Mon, Dec 04, 2023 at 06:56:27AM -0800, Yury Norov wrote:
> On Mon, Dec 04, 2023 at 12:50:41AM -0800, Souradeep Chakrabarti wrote:
> > Existing MANA design assigns IRQ to every CPU, including sibling
> > hyper-threads. This may cause multiple IRQs to be active simultaneously
> > in the same core and may reduce the network performance with RSS.
> > 
> > Improve the performance by assigning IRQ to non sibling CPUs in local
> > NUMA node.
> > 
> > Signed-off-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
> > ---
> > V3 -> V4:
> > * Used for_each_numa_hop_mask() macro and simplified the code.
> > Thanks to Yury Norov for the suggestion.
> 
> We've got a special tag for this:
> 
> Suggested-by: Yury Norov <yury.norov@gmali.com>
> 
> > * Added code to assign hwc irq separately in mana_gd_setup_irqs.
> > 
> > V2 -> V3:
> > * Created a helper function to get the next NUMA with CPU.
> > * Added some error checks for unsuccessful memory allocation.
> > * Fixed some comments on the code.
> > 
> > V1 -> V2:
> > * Simplified the code by removing filter_mask_list and using avail_cpus.
> > * Addressed infinite loop issue when there are numa nodes with no CPUs.
> > * Addressed uses of local numa node instead of 0 to start.
> > * Removed uses of BUG_ON.
> > * Placed cpus_read_lock in parent function to avoid num_online_cpus
> >   to get changed before function finishes the affinity assignment.
> > ---
> >  .../net/ethernet/microsoft/mana/gdma_main.c   | 70 +++++++++++++++++--
> >  1 file changed, 63 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > index 6367de0c2c2e..2194a53cce10 100644
> > --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > @@ -1243,15 +1243,57 @@ void mana_gd_free_res_map(struct gdma_resource *r)
> >  	r->size = 0;
> >  }
> >  
> > +static int irq_setup(int *irqs, int nvec, int start_numa_node)
> > +{
> > +	int i = 0, cpu, err = 0;
> > +	const struct cpumask *node_cpumask;
> > +	unsigned int  next_node = start_numa_node;
> > +	cpumask_var_t visited_cpus, node_cpumask_temp;
> > +
> > +	if (!zalloc_cpumask_var(&visited_cpus, GFP_KERNEL)) {
> > +		err = ENOMEM;
> > +		return err;
> > +	}
> > +	if (!zalloc_cpumask_var(&node_cpumask_temp, GFP_KERNEL)) {
> > +		err = -ENOMEM;
> > +		return err;
> > +	}
> 
> Can you add a bit more of vertical spacing?
> 
> > +	rcu_read_lock();
> > +	for_each_numa_hop_mask(node_cpumask, next_node) {
> > +		cpumask_copy(node_cpumask_temp, node_cpumask);
> > +		for_each_cpu(cpu, node_cpumask_temp) {
> > +			cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> > +				       topology_sibling_cpumask(cpu));
> > +			irq_set_affinity_and_hint(irqs[i], cpumask_of(cpu));
> > +			if (++i == nvec)
> > +				goto free_mask;
> > +			cpumask_set_cpu(cpu, visited_cpus);
> > +			if (cpumask_empty(node_cpumask_temp)) {
> > +				cpumask_copy(node_cpumask_temp, node_cpumask);
> > +				cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> > +					       visited_cpus);
> > +				cpu = 0;
> > +			}
> 
> It feels like you can calculate number of sibling groups in a hop in
> advance, so that you'll know how many IRQs you want to assign per each
> hop, and avoid resetting the node_cpumask_temp and spinning in inner
> loop for more than once...
> 
> Can you print your topology, and describe how you want to spread IRQs
> on it, and how your existing code does spread them?
>
The topology of one system is
> numactl -H
available: 2 nodes (0-1)
node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
node 0 size: 459521 MB
node 0 free: 456316 MB
node 1 cpus: 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143
144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168
169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191
node 1 size: 459617 MB
node 1 free: 456864 MB
node distances:
node   0   1
  0:  10  21
  1:  21  10
and I want to spread the IRQs in numa0 node first with 
CPU0 - IRQ0
CPU2 - IRQ1
CPU4 - IRQ2
CPU6 - IRQ3
---
---
---
CPU94 - IRQ47
then
CPU1 - IRQ48
CPU3 - IRQ49
CPU32 - IRQ64

In a topology where NUMA0 has 20 cores and NUMA1 has 20 cores, with total 80 CPUS, there I want
CPU0 - IRQ0
CPU2 - IRQ1
CPU4 - IRQ2
---
---
---
CPU38 - IRQ19
Then
CPU1 - IRQ20
CPU3 - IRQ21
---
---
CPU39 - IRQ39
Node1
CPU40 - IRQ40
CPU42 - IRQ41
CPU44 - IRQ42
---
CPU78 - IRQ58
CPU41 - IRQ59
CPU43 - IRQ60
---
---
CPU49 - IRQ64
 

Exisitng code : 
https://github.com/torvalds/linux/blob/master/drivers/net/ethernet/microsoft/mana/gdma_main.c#L1246

This uses cpumask_local_spread, so in a system where node has 64 cores, it spreads all 64+1 IRQs on
33 cores, rather than spreading it only on HT cores.

> Please add performance results in the commit message.
> 
> I feel like this may be a useful code for other kernel folks, and if
> so, we'd invest in it for more and make it a generic API, similar to
> cpumaks_local_spread()...
> 
> > +		}
> > +	}
> > +free_mask:
> > +	rcu_read_unlock();
> > +	free_cpumask_var(visited_cpus);
> > +	free_cpumask_var(node_cpumask_temp);
> > +	return err;
> > +}
> > +
> >  static int mana_gd_setup_irqs(struct pci_dev *pdev)
> >  {
> > -	unsigned int max_queues_per_port = num_online_cpus();
> >  	struct gdma_context *gc = pci_get_drvdata(pdev);
> > +	unsigned int max_queues_per_port;
> >  	struct gdma_irq_context *gic;
> >  	unsigned int max_irqs, cpu;
> > -	int nvec, irq;
> > +	int nvec, *irqs, irq;
> >  	int err, i = 0, j;
> >  
> > +	cpus_read_lock();
> > +	max_queues_per_port = num_online_cpus();
> >  	if (max_queues_per_port > MANA_MAX_NUM_QUEUES)
> >  		max_queues_per_port = MANA_MAX_NUM_QUEUES;
> >  
> > @@ -1261,6 +1303,11 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
> >  	nvec = pci_alloc_irq_vectors(pdev, 2, max_irqs, PCI_IRQ_MSIX);
> >  	if (nvec < 0)
> >  		return nvec;
> > +	irqs = kmalloc_array(max_queues_per_port, sizeof(int), GFP_KERNEL);
> > +	if (!irqs) {
> > +		err = -ENOMEM;
> > +		goto free_irq_vector;
> > +	}
> >  
> >  	gc->irq_contexts = kcalloc(nvec, sizeof(struct gdma_irq_context),
> >  				   GFP_KERNEL);
> > @@ -1287,21 +1334,28 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
> >  			goto free_irq;
> >  		}
> >  
> > -		err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
> > +		if (!i) {
> > +			err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
> > +			cpu = cpumask_local_spread(i, gc->numa_node);
> 
> If i == 0, you can simplify it because you just need the 1st CPU from
> a given node.
> 
> > +			irq_set_affinity_and_hint(irq, cpumask_of(cpu));
> > +		} else {
> > +			irqs[i - 1] = irq;
> > +			err = request_irq(irqs[i - 1], mana_gd_intr, 0, gic->name, gic);
> > +		}
> >  		if (err)
> >  			goto free_irq;
> > -
> > -		cpu = cpumask_local_spread(i, gc->numa_node);
> > -		irq_set_affinity_and_hint(irq, cpumask_of(cpu));
> >  	}
> >  
> > +	err = irq_setup(irqs, max_queues_per_port, gc->numa_node);
> > +	if (err)
> > +		goto free_irq;
> >  	err = mana_gd_alloc_res_map(nvec, &gc->msix_resource);
> >  	if (err)
> >  		goto free_irq;
> >  
> >  	gc->max_num_msix = nvec;
> >  	gc->num_msix_usable = nvec;
> > -
> > +	cpus_read_unlock();
> >  	return 0;
> >  
> >  free_irq:
> > @@ -1314,8 +1368,10 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
> >  	}
> >  
> >  	kfree(gc->irq_contexts);
> > +	kfree(irqs);
> >  	gc->irq_contexts = NULL;
> >  free_irq_vector:
> > +	cpus_read_unlock();
> >  	pci_free_irq_vectors(pdev);
> >  	return err;
> >  }
> > -- 
> > 2.34.1
  

On Tue, Dec 05, 2023 at 03:01:38AM -0800, Souradeep Chakrabarti wrote:
> > > diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > index 6367de0c2c2e..2194a53cce10 100644
> > > --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > @@ -1243,15 +1243,57 @@ void mana_gd_free_res_map(struct gdma_resource *r)
> > >  	r->size = 0;
> > >  }
> > >  
> > > +static int irq_setup(int *irqs, int nvec, int start_numa_node)
> > > +{
> > > +	int i = 0, cpu, err = 0;
> > > +	const struct cpumask *node_cpumask;
> > > +	unsigned int  next_node = start_numa_node;
> > > +	cpumask_var_t visited_cpus, node_cpumask_temp;
> > > +
> > > +	if (!zalloc_cpumask_var(&visited_cpus, GFP_KERNEL)) {
> > > +		err = ENOMEM;
> > > +		return err;
> > > +	}
> > > +	if (!zalloc_cpumask_var(&node_cpumask_temp, GFP_KERNEL)) {
> > > +		err = -ENOMEM;
> > > +		return err;
> > > +	}
> > 
> > Can you add a bit more of vertical spacing?
> > 
> > > +	rcu_read_lock();
> > > +	for_each_numa_hop_mask(node_cpumask, next_node) {
> > > +		cpumask_copy(node_cpumask_temp, node_cpumask);
> > > +		for_each_cpu(cpu, node_cpumask_temp) {
> > > +			cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> > > +				       topology_sibling_cpumask(cpu));
> > > +			irq_set_affinity_and_hint(irqs[i], cpumask_of(cpu));
> > > +			if (++i == nvec)
> > > +				goto free_mask;
> > > +			cpumask_set_cpu(cpu, visited_cpus);
> > > +			if (cpumask_empty(node_cpumask_temp)) {
> > > +				cpumask_copy(node_cpumask_temp, node_cpumask);
> > > +				cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> > > +					       visited_cpus);
> > > +				cpu = 0;
> > > +			}
> > 
> > It feels like you can calculate number of sibling groups in a hop in
> > advance, so that you'll know how many IRQs you want to assign per each
> > hop, and avoid resetting the node_cpumask_temp and spinning in inner
> > loop for more than once...
> > 
> > Can you print your topology, and describe how you want to spread IRQs
> > on it, and how your existing code does spread them?
> >
> The topology of one system is
> > numactl -H
> available: 2 nodes (0-1)
> node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
> 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
> 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
> node 0 size: 459521 MB
> node 0 free: 456316 MB
> node 1 cpus: 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
> 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143
> 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168
> 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191
> node 1 size: 459617 MB
> node 1 free: 456864 MB
> node distances:
> node   0   1
>   0:  10  21
>   1:  21  10
> and I want to spread the IRQs in numa0 node first with 
> CPU0 - IRQ0
> CPU2 - IRQ1
> CPU4 - IRQ2
> CPU6 - IRQ3
> ---
> ---
> ---
> CPU94 - IRQ47
> then
> CPU1 - IRQ48
> CPU3 - IRQ49
> CPU32 - IRQ64
> 
> In a topology where NUMA0 has 20 cores and NUMA1 has 20 cores, with total 80 CPUS, there I want
> CPU0 - IRQ0
> CPU2 - IRQ1
> CPU4 - IRQ2
> ---
> ---
> ---
> CPU38 - IRQ19
> Then
> CPU1 - IRQ20
> CPU3 - IRQ21
> ---
> ---
> CPU39 - IRQ39
> Node1
> CPU40 - IRQ40
> CPU42 - IRQ41
> CPU44 - IRQ42
> ---
> CPU78 - IRQ58
> CPU41 - IRQ59
> CPU43 - IRQ60
> ---
> ---
> CPU49 - IRQ64
>  
> 
> Exisitng code : 
> https://github.com/torvalds/linux/blob/master/drivers/net/ethernet/microsoft/mana/gdma_main.c#L1246
> 
> This uses cpumask_local_spread, so in a system where node has 64 cores, it spreads all 64+1 IRQs on
> 33 cores, rather than spreading it only on HT cores.

So from what you said, it looks like you're trying to implement the
following heuristics:

1. No more than one IRQ per CPU, if possible;
2. NUMA locality is the second priority;
3. Sibling dislocality is the last priority;

Can you confirm that?

If the above correct, your code is quite close to what you want except
that for every new hop (outer loop) you have to clear CPUs belonging to
previous hop, which is in you case the same as visited_cpus mask.

But I think you can do it even better if just account the number of
assigned IRQs. That way you can get rid of the most of housekeeping
code.

const struct cpumask *next, *prev = cpu_none_mask;

for_each_numa_hop_mask(next, node) {
        cpumask_and_not(curr, next, prev);

        for (w = cpumask_weight(curr), cnt = 0; cnt < w; cnt++)
                cpumask_copy(cpus, curr);
                for_each_cpu(cpu, cpus) {
                        if (i++ == nvec)
                                goto done;

                        cpumask_andnot(cpus, cpus, topology_sibling_cpumask(cpu));
                        irq_set_affinity_and_hint(irqs[i], topology_sibling_cpumask(cpu)); // [*]
                }
        }
        prev = next;
}

[*] I already mentioned that in v3, and also asking here: if you're saying
that wrt IRQs distribution, all CPUs belonging to the same sibling group
are the same, why don't you assign all the group to the IRQ. It gives the
system flexibility to balance workload better.

Let's consider this topology:

Node            0               1
Core        0       1       2       3
CPU       0   1   2   3   4   5   6   7

The code above should create the following mapping for the IRQs:
IRQ     Nodes   Cores   CPUs
0       1       0       0-1
1       1       1       2-3
2       1       0       0-1
3       1       1       2-3
4       2       2       4-5
5       2       3       6-7
6       2       2       4-5
7       2       3       6-7

This is pretty close to what I proposed in v3, except that it flips
priorities of NUMA locality vs sibling dislocality. My original
suggestion is simpler in implementation and aligns with my natural
feeling of 'fair' IRQ distribution.

Can you make sure that your heuristics are the best wrt performance?

Regarding the rest of the discussion, I think that for_each_numa_hop_mask() 
together with some basic cpumaks operations results quite a readable
and maintainable code, and we don't need any more generic API to
support this type of distribution tasks.

What do you think guys?

Thanks,
Yury
  

On Tue, Dec 05, 2023 at 02:52:06PM -0800, Yury Norov wrote:
> On Tue, Dec 05, 2023 at 03:01:38AM -0800, Souradeep Chakrabarti wrote:
> > > > diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > > index 6367de0c2c2e..2194a53cce10 100644
> > > > --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > > +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > > @@ -1243,15 +1243,57 @@ void mana_gd_free_res_map(struct gdma_resource *r)
> > > >  	r->size = 0;
> > > >  }
> > > >  
> > > > +static int irq_setup(int *irqs, int nvec, int start_numa_node)
> > > > +{
> > > > +	int i = 0, cpu, err = 0;
> > > > +	const struct cpumask *node_cpumask;
> > > > +	unsigned int  next_node = start_numa_node;
> > > > +	cpumask_var_t visited_cpus, node_cpumask_temp;
> > > > +
> > > > +	if (!zalloc_cpumask_var(&visited_cpus, GFP_KERNEL)) {
> > > > +		err = ENOMEM;
> > > > +		return err;
> > > > +	}
> > > > +	if (!zalloc_cpumask_var(&node_cpumask_temp, GFP_KERNEL)) {
> > > > +		err = -ENOMEM;
> > > > +		return err;
> > > > +	}
> > > 
> > > Can you add a bit more of vertical spacing?
> > > 
> > > > +	rcu_read_lock();
> > > > +	for_each_numa_hop_mask(node_cpumask, next_node) {
> > > > +		cpumask_copy(node_cpumask_temp, node_cpumask);
> > > > +		for_each_cpu(cpu, node_cpumask_temp) {
> > > > +			cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> > > > +				       topology_sibling_cpumask(cpu));
> > > > +			irq_set_affinity_and_hint(irqs[i], cpumask_of(cpu));
> > > > +			if (++i == nvec)
> > > > +				goto free_mask;
> > > > +			cpumask_set_cpu(cpu, visited_cpus);
> > > > +			if (cpumask_empty(node_cpumask_temp)) {
> > > > +				cpumask_copy(node_cpumask_temp, node_cpumask);
> > > > +				cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> > > > +					       visited_cpus);
> > > > +				cpu = 0;
> > > > +			}
> > > 
> > > It feels like you can calculate number of sibling groups in a hop in
> > > advance, so that you'll know how many IRQs you want to assign per each
> > > hop, and avoid resetting the node_cpumask_temp and spinning in inner
> > > loop for more than once...
> > > 
> > > Can you print your topology, and describe how you want to spread IRQs
> > > on it, and how your existing code does spread them?
> > >
> > The topology of one system is
> > > numactl -H
> > available: 2 nodes (0-1)
> > node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
> > 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
> > 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
> > node 0 size: 459521 MB
> > node 0 free: 456316 MB
> > node 1 cpus: 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
> > 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143
> > 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168
> > 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191
> > node 1 size: 459617 MB
> > node 1 free: 456864 MB
> > node distances:
> > node   0   1
> >   0:  10  21
> >   1:  21  10
> > and I want to spread the IRQs in numa0 node first with 
> > CPU0 - IRQ0
> > CPU2 - IRQ1
> > CPU4 - IRQ2
> > CPU6 - IRQ3
> > ---
> > ---
> > ---
> > CPU94 - IRQ47
> > then
> > CPU1 - IRQ48
> > CPU3 - IRQ49
> > CPU32 - IRQ64
> > 
> > In a topology where NUMA0 has 20 cores and NUMA1 has 20 cores, with total 80 CPUS, there I want
> > CPU0 - IRQ0
> > CPU2 - IRQ1
> > CPU4 - IRQ2
> > ---
> > ---
> > ---
> > CPU38 - IRQ19
> > Then
> > CPU1 - IRQ20
> > CPU3 - IRQ21
> > ---
> > ---
> > CPU39 - IRQ39
> > Node1
> > CPU40 - IRQ40
> > CPU42 - IRQ41
> > CPU44 - IRQ42
> > ---
> > CPU78 - IRQ58
> > CPU41 - IRQ59
> > CPU43 - IRQ60
> > ---
> > ---
> > CPU49 - IRQ64
> >  
> > 
> > Exisitng code : 
> > https://github.com/torvalds/linux/blob/master/drivers/net/ethernet/microsoft/mana/gdma_main.c#L1246
> > 
> > This uses cpumask_local_spread, so in a system where node has 64 cores, it spreads all 64+1 IRQs on
> > 33 cores, rather than spreading it only on HT cores.
> 
> So from what you said, it looks like you're trying to implement the
> following heuristics:
> 
> 1. No more than one IRQ per CPU, if possible;
> 2. NUMA locality is the second priority;
> 3. Sibling dislocality is the last priority;
> 
> Can you confirm that?
> 
The idea is pretty similar, only change is that if there are enough cpu
cores in the NUMA node, then no more than one IRQ per core, if possible.
So the behaviour will be :
1. no more than one IRQ per core, if possible.
2. No more than one IRQ per CPU, if possible
3. NUMA locality is the second priority;
4. Sibling dislocality is the last priority;
> If the above correct, your code is quite close to what you want except
> that for every new hop (outer loop) you have to clear CPUs belonging to
> previous hop, which is in you case the same as visited_cpus mask.
> 
> But I think you can do it even better if just account the number of
> assigned IRQs. That way you can get rid of the most of housekeeping
> code.
> 
> const struct cpumask *next, *prev = cpu_none_mask;
> 
> for_each_numa_hop_mask(next, node) {
>         cpumask_and_not(curr, next, prev);
> 
>         for (w = cpumask_weight(curr), cnt = 0; cnt < w; cnt++)
>                 cpumask_copy(cpus, curr);
>                 for_each_cpu(cpu, cpus) {
>                         if (i++ == nvec)
>                                 goto done;
> 
>                         cpumask_andnot(cpus, cpus, topology_sibling_cpumask(cpu));
>                         irq_set_affinity_and_hint(irqs[i], topology_sibling_cpumask(cpu)); // [*]
>                 }
>         }
>         prev = next;
> }
> 
> [*] I already mentioned that in v3, and also asking here: if you're saying
> that wrt IRQs distribution, all CPUs belonging to the same sibling group
> are the same, why don't you assign all the group to the IRQ. It gives the
> system flexibility to balance workload better.
> 
> Let's consider this topology:
> 
> Node            0               1
> Core        0       1       2       3
> CPU       0   1   2   3   4   5   6   7
> 
> The code above should create the following mapping for the IRQs:
> IRQ     Nodes   Cores   CPUs
> 0       1       0       0-1
> 1       1       1       2-3
> 2       1       0       0-1
> 3       1       1       2-3
> 4       2       2       4-5
> 5       2       3       6-7
> 6       2       2       4-5
> 7       2       3       6-7
> 
Thanks for the suggestion, but as mentioned by me above, that if enough
cores are available in a numa noed, then will assign one IRQ per core, rather
than each CPU. That is the reason we are moving away from using cpumask_local_spread().
As it assign in every cpu in the numa, irrespective of if there are enough cores
to accomodate the IRQs. That is why I am first trying to assign one irq per core
till all the cores in the NUMA node are used.
> This is pretty close to what I proposed in v3, except that it flips
> priorities of NUMA locality vs sibling dislocality. My original
> suggestion is simpler in implementation and aligns with my natural
> feeling of 'fair' IRQ distribution.
> 
> Can you make sure that your heuristics are the best wrt performance?
> 
Yes, I had done multiple perf analysis using ntttcp and we got approximately
12-15 percent improvement.
> Regarding the rest of the discussion, I think that for_each_numa_hop_mask() 
> together with some basic cpumaks operations results quite a readable
> and maintainable code, and we don't need any more generic API to
> support this type of distribution tasks.
>
I will share the V5 patch soon, which does fix the mask issue from V4 and
also tries to assign IRQ0 to separate CPU if enough CPUs are available. 
> What do you think guys?
> 
> Thanks,
> Yury
  

On Tue, Dec 05, 2023 at 02:52:06PM -0800, Yury Norov wrote:
> On Tue, Dec 05, 2023 at 03:01:38AM -0800, Souradeep Chakrabarti wrote:
> > > > diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > > index 6367de0c2c2e..2194a53cce10 100644
> > > > --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > > +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> > > > @@ -1243,15 +1243,57 @@ void mana_gd_free_res_map(struct gdma_resource *r)
> > > >  	r->size = 0;
> > > >  }
> > > >  
> > > > +static int irq_setup(int *irqs, int nvec, int start_numa_node)
> > > > +{
> > > > +	int i = 0, cpu, err = 0;
> > > > +	const struct cpumask *node_cpumask;
> > > > +	unsigned int  next_node = start_numa_node;
> > > > +	cpumask_var_t visited_cpus, node_cpumask_temp;
> > > > +
> > > > +	if (!zalloc_cpumask_var(&visited_cpus, GFP_KERNEL)) {
> > > > +		err = ENOMEM;
> > > > +		return err;
> > > > +	}
> > > > +	if (!zalloc_cpumask_var(&node_cpumask_temp, GFP_KERNEL)) {
> > > > +		err = -ENOMEM;
> > > > +		return err;
> > > > +	}
> > > 
> > > Can you add a bit more of vertical spacing?
> > > 
> > > > +	rcu_read_lock();
> > > > +	for_each_numa_hop_mask(node_cpumask, next_node) {
> > > > +		cpumask_copy(node_cpumask_temp, node_cpumask);
> > > > +		for_each_cpu(cpu, node_cpumask_temp) {
> > > > +			cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> > > > +				       topology_sibling_cpumask(cpu));
> > > > +			irq_set_affinity_and_hint(irqs[i], cpumask_of(cpu));
> > > > +			if (++i == nvec)
> > > > +				goto free_mask;
> > > > +			cpumask_set_cpu(cpu, visited_cpus);
> > > > +			if (cpumask_empty(node_cpumask_temp)) {
> > > > +				cpumask_copy(node_cpumask_temp, node_cpumask);
> > > > +				cpumask_andnot(node_cpumask_temp, node_cpumask_temp,
> > > > +					       visited_cpus);
> > > > +				cpu = 0;
> > > > +			}
> > > 
> > > It feels like you can calculate number of sibling groups in a hop in
> > > advance, so that you'll know how many IRQs you want to assign per each
> > > hop, and avoid resetting the node_cpumask_temp and spinning in inner
> > > loop for more than once...
> > > 
> > > Can you print your topology, and describe how you want to spread IRQs
> > > on it, and how your existing code does spread them?
> > >
> > The topology of one system is
> > > numactl -H
> > available: 2 nodes (0-1)
> > node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
> > 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
> > 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
> > node 0 size: 459521 MB
> > node 0 free: 456316 MB
> > node 1 cpus: 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
> > 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143
> > 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168
> > 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191
> > node 1 size: 459617 MB
> > node 1 free: 456864 MB
> > node distances:
> > node   0   1
> >   0:  10  21
> >   1:  21  10
> > and I want to spread the IRQs in numa0 node first with 
> > CPU0 - IRQ0
> > CPU2 - IRQ1
> > CPU4 - IRQ2
> > CPU6 - IRQ3
> > ---
> > ---
> > ---
> > CPU94 - IRQ47
> > then
> > CPU1 - IRQ48
> > CPU3 - IRQ49
> > CPU32 - IRQ64
> > 
> > In a topology where NUMA0 has 20 cores and NUMA1 has 20 cores, with total 80 CPUS, there I want
> > CPU0 - IRQ0
> > CPU2 - IRQ1
> > CPU4 - IRQ2
> > ---
> > ---
> > ---
> > CPU38 - IRQ19
> > Then
> > CPU1 - IRQ20
> > CPU3 - IRQ21
> > ---
> > ---
> > CPU39 - IRQ39
> > Node1
> > CPU40 - IRQ40
> > CPU42 - IRQ41
> > CPU44 - IRQ42
> > ---
> > CPU78 - IRQ58
> > CPU41 - IRQ59
> > CPU43 - IRQ60
> > ---
> > ---
> > CPU49 - IRQ64
> >  
> > 
> > Exisitng code : 
> > https://github.com/torvalds/linux/blob/master/drivers/net/ethernet/microsoft/mana/gdma_main.c#L1246
> > 
> > This uses cpumask_local_spread, so in a system where node has 64 cores, it spreads all 64+1 IRQs on
> > 33 cores, rather than spreading it only on HT cores.
> 
> So from what you said, it looks like you're trying to implement the
> following heuristics:
> 
> 1. No more than one IRQ per CPU, if possible;
> 2. NUMA locality is the second priority;
> 3. Sibling dislocality is the last priority;
> 
> Can you confirm that?
> 
> If the above correct, your code is quite close to what you want except
> that for every new hop (outer loop) you have to clear CPUs belonging to
> previous hop, which is in you case the same as visited_cpus mask.
> 
> But I think you can do it even better if just account the number of
> assigned IRQs. That way you can get rid of the most of housekeeping
> code.
> 
> const struct cpumask *next, *prev = cpu_none_mask;
> 
> for_each_numa_hop_mask(next, node) {
>         cpumask_and_not(curr, next, prev);
> 
>         for (w = cpumask_weight(curr), cnt = 0; cnt < w; cnt++)
>                 cpumask_copy(cpus, curr);
>                 for_each_cpu(cpu, cpus) {
>                         if (i++ == nvec)
>                                 goto done;
> 
>                         cpumask_andnot(cpus, cpus, topology_sibling_cpumask(cpu));
>                         irq_set_affinity_and_hint(irqs[i], topology_sibling_cpumask(cpu)); // [*]
>                 }
>         }
>         prev = next;
> }
I am experimenting with the proposal here, and based on the result will
update the V5 patch.
> 
> [*] I already mentioned that in v3, and also asking here: if you're saying
> that wrt IRQs distribution, all CPUs belonging to the same sibling group
> are the same, why don't you assign all the group to the IRQ. It gives the
> system flexibility to balance workload better.
> 
> Let's consider this topology:
> 
> Node            0               1
> Core        0       1       2       3
> CPU       0   1   2   3   4   5   6   7
> 
> The code above should create the following mapping for the IRQs:
> IRQ     Nodes   Cores   CPUs
> 0       1       0       0-1
> 1       1       1       2-3
> 2       1       0       0-1
> 3       1       1       2-3
> 4       2       2       4-5
> 5       2       3       6-7
> 6       2       2       4-5
> 7       2       3       6-7
> 
> This is pretty close to what I proposed in v3, except that it flips
> priorities of NUMA locality vs sibling dislocality. My original
> suggestion is simpler in implementation and aligns with my natural
> feeling of 'fair' IRQ distribution.
> 
> Can you make sure that your heuristics are the best wrt performance?
> 
> Regarding the rest of the discussion, I think that for_each_numa_hop_mask() 
> together with some basic cpumaks operations results quite a readable
> and maintainable code, and we don't need any more generic API to
> support this type of distribution tasks.
> 
> What do you think guys?
> 
> Thanks,
> Yury