[Patch V3 4/9] openvswitch: Replace cpu_to_node() with cpu_to_mem() to support memoryless node

[Patch V3 4/9] openvswitch: Replace cpu_to_node() with cpu_to_mem() to support memoryless node

[Jiang Liu]

Function ovs_flow_stats_update() allocates memory with __GFP_THISNODE
flag set, which may cause permanent memory allocation failure on
memoryless node. So replace cpu_to_node() with cpu_to_mem() to better
support memoryless node. For node with memory, cpu_to_mem() is the same
as cpu_to_node().

This change only affects performance and shouldn't affect functionality.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 net/openvswitch/flow.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index bc7b0aba994a..e50a5681d0c2 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -69,7 +69,7 @@ void ovs_flow_stats_update(struct sw_flow *flow, __be16 tcp_flags,
 			   const struct sk_buff *skb)
 {
 	struct flow_stats *stats;
-	int node = numa_node_id();
+	int node = numa_mem_id();
 	int len = skb->len + (skb_vlan_tag_present(skb) ? VLAN_HLEN : 0);
 
 	stats = rcu_dereference(flow->stats[node]);
-- 
1.7.10.4

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[Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node

[Jiang Liu]

Function i40e_clean_rx_irq() tries to reuse memory pages allocated
from the nearest node. To better support memoryless node, use
numa_mem_id() instead of numa_node_id() to get the nearest node with
memory.

This change should only affect performance.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 9a4f2bc70cd2..a8f618cb8eb0 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -1516,7 +1516,7 @@ static int i40e_clean_rx_irq_ps(struct i40e_ring *rx_ring, int budget)
 	unsigned int total_rx_bytes = 0, total_rx_packets = 0;
 	u16 rx_packet_len, rx_header_len, rx_sph, rx_hbo;
 	u16 cleaned_count = I40E_DESC_UNUSED(rx_ring);
-	const int current_node = numa_node_id();
+	const int current_node = numa_mem_id();
 	struct i40e_vsi *vsi = rx_ring->vsi;
 	u16 i = rx_ring->next_to_clean;
 	union i40e_rx_desc *rx_desc;
-- 
1.7.10.4

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[Patch V3 6/9] i40evf: Use numa_mem_id() to better support memoryless node

[Jiang Liu]

Function i40e_clean_rx_irq() tries to reuse memory pages allocated
from the nearest node. To better support memoryless node, use
numa_mem_id() instead of numa_node_id() to get the nearest node with
memory.

This change should only affect performance.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 drivers/net/ethernet/intel/i40evf/i40e_txrx.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index 395f32f226c0..19ca96d8bd97 100644
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -1003,7 +1003,7 @@ static int i40e_clean_rx_irq_ps(struct i40e_ring *rx_ring, int budget)
 	unsigned int total_rx_bytes = 0, total_rx_packets = 0;
 	u16 rx_packet_len, rx_header_len, rx_sph, rx_hbo;
 	u16 cleaned_count = I40E_DESC_UNUSED(rx_ring);
-	const int current_node = numa_node_id();
+	const int current_node = numa_mem_id();
 	struct i40e_vsi *vsi = rx_ring->vsi;
 	u16 i = rx_ring->next_to_clean;
 	union i40e_rx_desc *rx_desc;
-- 
1.7.10.4

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RE: [Intel-wired-lan] [Patch V3 6/9] i40evf: Use numa_mem_id() to better support memoryless node

[Patil, Kiran]

ACK.

Thanks,
-- Kiran P.

-----Original Message-----
From: Intel-wired-lan [mailto:intel-wired-lan-bounces@lists.osuosl.org] On Behalf Of Jiang Liu
Sent: Sunday, August 16, 2015 8:19 PM
To: Andrew Morton; Mel Gorman; David Rientjes; Mike Galbraith; Peter Zijlstra; Wysocki, Rafael J; Tang Chen; Tejun Heo; Kirsher, Jeffrey T; Brandeburg, Jesse; Nelson, Shannon; Wyborny, Carolyn; Skidmore, Donald C; Vick, Matthew; Ronciak, John; Williams, Mitch A
Cc: Luck, Tony; netdev@vger.kernel.org; x86@kernel.org; linux-hotplug@vger.kernel.org; linux-kernel@vger.kernel.org; linux-mm@kvack.org; intel-wired-lan@lists.osuosl.org; Jiang Liu
Subject: [Intel-wired-lan] [Patch V3 6/9] i40evf: Use numa_mem_id() to better support memoryless node

Function i40e_clean_rx_irq() tries to reuse memory pages allocated from the nearest node. To better support memoryless node, use
numa_mem_id() instead of numa_node_id() to get the nearest node with memory.

This change should only affect performance.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 drivers/net/ethernet/intel/i40evf/i40e_txrx.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index 395f32f226c0..19ca96d8bd97 100644
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -1003,7 +1003,7 @@ static int i40e_clean_rx_irq_ps(struct i40e_ring *rx_ring, int budget)
 	unsigned int total_rx_bytes = 0, total_rx_packets = 0;
 	u16 rx_packet_len, rx_header_len, rx_sph, rx_hbo;
 	u16 cleaned_count = I40E_DESC_UNUSED(rx_ring);
-	const int current_node = numa_node_id();
+	const int current_node = numa_mem_id();
 	struct i40e_vsi *vsi = rx_ring->vsi;
 	u16 i = rx_ring->next_to_clean;
 	union i40e_rx_desc *rx_desc;
--
1.7.10.4

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Re: [Patch V3 4/9] openvswitch: Replace cpu_to_node() with cpu_to_mem() to support memoryless node

[Pravin Shelar]

On Sun, Aug 16, 2015 at 8:19 PM, Jiang Liu <jiang.liu@linux.intel.com> wrote:
> Function ovs_flow_stats_update() allocates memory with __GFP_THISNODE
> flag set, which may cause permanent memory allocation failure on
> memoryless node. So replace cpu_to_node() with cpu_to_mem() to better
> support memoryless node. For node with memory, cpu_to_mem() is the same
> as cpu_to_node().
>
> This change only affects performance and shouldn't affect functionality.
>
> Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>

Acked-by: Pravin B Shelar <pshelar@nicira.com>

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Re: [Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node

[David Rientjes]

On Mon, 17 Aug 2015, Jiang Liu wrote:

> Function i40e_clean_rx_irq() tries to reuse memory pages allocated

s/i40e_clean_rx_irq/i40e_clean_rx_irq_ps/

> from the nearest node. To better support memoryless node, use
> numa_mem_id() instead of numa_node_id() to get the nearest node with
> memory.
> 

Out of curiosity, what prevents the cpu to be preempted and current_node 
to no longer match numa_mem_id()?

> This change should only affect performance.
> 
> Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_txrx.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> index 9a4f2bc70cd2..a8f618cb8eb0 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> @@ -1516,7 +1516,7 @@ static int i40e_clean_rx_irq_ps(struct i40e_ring *rx_ring, int budget)
>  	unsigned int total_rx_bytes = 0, total_rx_packets = 0;
>  	u16 rx_packet_len, rx_header_len, rx_sph, rx_hbo;
>  	u16 cleaned_count = I40E_DESC_UNUSED(rx_ring);
> -	const int current_node = numa_node_id();
> +	const int current_node = numa_mem_id();
>  	struct i40e_vsi *vsi = rx_ring->vsi;
>  	u16 i = rx_ring->next_to_clean;
>  	union i40e_rx_desc *rx_desc;

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RE: [Intel-wired-lan] [Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node

[Patil, Kiran]

Acked-by: Kiran Patil <kiran.patil@intel.com>

-----Original Message-----
From: Intel-wired-lan [mailto:intel-wired-lan-bounces@lists.osuosl.org] On Behalf Of Jiang Liu
Sent: Sunday, August 16, 2015 8:19 PM
To: Andrew Morton; Mel Gorman; David Rientjes; Mike Galbraith; Peter Zijlstra; Wysocki, Rafael J; Tang Chen; Tejun Heo; Kirsher, Jeffrey T; Brandeburg, Jesse; Nelson, Shannon; Wyborny, Carolyn; Skidmore, Donald C; Vick, Matthew; Ronciak, John; Williams, Mitch A
Cc: Luck, Tony; netdev@vger.kernel.org; x86@kernel.org; linux-hotplug@vger.kernel.org; linux-kernel@vger.kernel.org; linux-mm@kvack.org; intel-wired-lan@lists.osuosl.org; Jiang Liu
Subject: [Intel-wired-lan] [Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node

Function i40e_clean_rx_irq() tries to reuse memory pages allocated from the nearest node. To better support memoryless node, use
numa_mem_id() instead of numa_node_id() to get the nearest node with memory.

This change should only affect performance.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 9a4f2bc70cd2..a8f618cb8eb0 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -1516,7 +1516,7 @@ static int i40e_clean_rx_irq_ps(struct i40e_ring *rx_ring, int budget)
 	unsigned int total_rx_bytes = 0, total_rx_packets = 0;
 	u16 rx_packet_len, rx_header_len, rx_sph, rx_hbo;
 	u16 cleaned_count = I40E_DESC_UNUSED(rx_ring);
-	const int current_node = numa_node_id();
+	const int current_node = numa_mem_id();
 	struct i40e_vsi *vsi = rx_ring->vsi;
 	u16 i = rx_ring->next_to_clean;
 	union i40e_rx_desc *rx_desc;
--
1.7.10.4

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RE: [Intel-wired-lan] [Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node

[David Rientjes]

On Wed, 19 Aug 2015, Patil, Kiran wrote:

> Acked-by: Kiran Patil <kiran.patil@intel.com>

Where's the call to preempt_disable() to prevent kernels with preemption 
from making numa_node_id() invalid during this iteration?

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Re: [Intel-wired-lan] [Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node

[Andrew Morton]

On Wed, 19 Aug 2015 17:18:15 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:

> On Wed, 19 Aug 2015, Patil, Kiran wrote:
> 
> > Acked-by: Kiran Patil <kiran.patil@intel.com>
> 
> Where's the call to preempt_disable() to prevent kernels with preemption 
> from making numa_node_id() invalid during this iteration?

David asked this question twice, received no answer and now the patch
is in the maintainer tree, destined for mainline.

If I was asked this question I would respond

  The use of numa_mem_id() is racy and best-effort.  If the unlikely
  race occurs, the memory allocation will occur on the wrong node, the
  overall result being very slightly suboptimal performance.  The
  existing use of numa_node_id() suffers from the same issue.

But I'm not the person proposing the patch.  Please don't just ignore
reviewer comments!

Re: [Intel-wired-lan] [Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node

[Jiang Liu]

On 2015/10/9 4:20, Andrew Morton wrote:
> On Wed, 19 Aug 2015 17:18:15 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:
> 
>> On Wed, 19 Aug 2015, Patil, Kiran wrote:
>>
>>> Acked-by: Kiran Patil <kiran.patil@intel.com>
>>
>> Where's the call to preempt_disable() to prevent kernels with preemption 
>> from making numa_node_id() invalid during this iteration?
> 
> David asked this question twice, received no answer and now the patch
> is in the maintainer tree, destined for mainline.
> 
> If I was asked this question I would respond
> 
>   The use of numa_mem_id() is racy and best-effort.  If the unlikely
>   race occurs, the memory allocation will occur on the wrong node, the
>   overall result being very slightly suboptimal performance.  The
>   existing use of numa_node_id() suffers from the same issue.
> 
> But I'm not the person proposing the patch.  Please don't just ignore
> reviewer comments!
Hi Andrew,
	Apologize for the slow response due to personal reasons!
And thanks for answering the question from David. To be honest,
I didn't know how to answer this question before. Actually this
question has puzzled me for a long time when dealing with memory
hot-removal. For normal cases, it only causes sub-optimal memory
allocation if schedule event happens between querying NUMA node id
and calling alloc_pages_node(). But what happens if system run into
following execution sequence?
1) node = numa_mem_id();
2) memory hot-removal event triggers
2.1) remove affected memory
2.2) reset pgdat to zero if node becomes empty after memory removal
3) alloc_pages_node(), which may access zero-ed pgdat structure.

I haven't found a mechanism to protect system from above sequence yet,
so puzzled for a long time already:(. Does stop_machine() protect
system from such a execution sequence?
Thanks!
Gerry

> 
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Re: [Intel-wired-lan] [Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node

[Kamezawa Hiroyuki]

On 2015/10/09 14:52, Jiang Liu wrote:
> On 2015/10/9 4:20, Andrew Morton wrote:
>> On Wed, 19 Aug 2015 17:18:15 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:
>>
>>> On Wed, 19 Aug 2015, Patil, Kiran wrote:
>>>
>>>> Acked-by: Kiran Patil <kiran.patil@intel.com>
>>>
>>> Where's the call to preempt_disable() to prevent kernels with preemption
>>> from making numa_node_id() invalid during this iteration?
>>
>> David asked this question twice, received no answer and now the patch
>> is in the maintainer tree, destined for mainline.
>>
>> If I was asked this question I would respond
>>
>>    The use of numa_mem_id() is racy and best-effort.  If the unlikely
>>    race occurs, the memory allocation will occur on the wrong node, the
>>    overall result being very slightly suboptimal performance.  The
>>    existing use of numa_node_id() suffers from the same issue.
>>
>> But I'm not the person proposing the patch.  Please don't just ignore
>> reviewer comments!
> Hi Andrew,
> 	Apologize for the slow response due to personal reasons!
> And thanks for answering the question from David. To be honest,
> I didn't know how to answer this question before. Actually this
> question has puzzled me for a long time when dealing with memory
> hot-removal. For normal cases, it only causes sub-optimal memory
> allocation if schedule event happens between querying NUMA node id
> and calling alloc_pages_node(). But what happens if system run into
> following execution sequence?
> 1) node = numa_mem_id();
> 2) memory hot-removal event triggers
> 2.1) remove affected memory
> 2.2) reset pgdat to zero if node becomes empty after memory removal

I'm sorry if I misunderstand something.
After commit b0dc3a342af36f95a68fe229b8f0f73552c5ca08, there is no memset().

> 3) alloc_pages_node(), which may access zero-ed pgdat structure.

?

>
> I haven't found a mechanism to protect system from above sequence yet,
> so puzzled for a long time already:(. Does stop_machine() protect
> system from such a execution sequence?

To access pgdat, a pgdat's zone should be on per-pgdat-zonelist.
Now, __build_all_zonelists() is called under stop_machine(). That's the reason
why you're asking what stop_machine() does. And, as you know, stop_machine() is not
protecting anything. The caller may fallback into removed zone.

Then, let's think.

At first, please note "pgdat" is not removed (and cannot be removed),
accessing pgdat's memory will not cause segmentation fault.

Just contents are problem. At removal, zone's page related information
and pgdat's page related information is cleared.

alloc_pages uses zonelist/zoneref/cache to walk each zones without accessing
pgdat itself. I think accessing zonelist is safe because it's an array updated
by stop_machine().

So, the problem is alloc_pages() can work correctly even if zone contains no page.
I think it should work.

(Note: zones are included in pgdat. So, zeroing pgdat means zeroing zone and other
  structures. it will not work.)

So, what problem you see now ?
I'm sorry I can't chase old discusions.

Thanks,
-Kame















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Re: [Intel-wired-lan] [Patch V3 5/9] i40e: Use numa_mem_id() to better support memoryless node

[Jiang Liu]

On 2015/10/9 17:08, Kamezawa Hiroyuki wrote:
> On 2015/10/09 14:52, Jiang Liu wrote:
>> On 2015/10/9 4:20, Andrew Morton wrote:
>>> On Wed, 19 Aug 2015 17:18:15 -0700 (PDT) David Rientjes
>>> <rientjes@google.com> wrote:
>>>
>>>> On Wed, 19 Aug 2015, Patil, Kiran wrote:
>>>>
>>>>> Acked-by: Kiran Patil <kiran.patil@intel.com>
>>>>
>>>> Where's the call to preempt_disable() to prevent kernels with
>>>> preemption
>>>> from making numa_node_id() invalid during this iteration?
>>>
>>> David asked this question twice, received no answer and now the patch
>>> is in the maintainer tree, destined for mainline.
>>>
>>> If I was asked this question I would respond
>>>
>>>    The use of numa_mem_id() is racy and best-effort.  If the unlikely
>>>    race occurs, the memory allocation will occur on the wrong node, the
>>>    overall result being very slightly suboptimal performance.  The
>>>    existing use of numa_node_id() suffers from the same issue.
>>>
>>> But I'm not the person proposing the patch.  Please don't just ignore
>>> reviewer comments!
>> Hi Andrew,
>>     Apologize for the slow response due to personal reasons!
>> And thanks for answering the question from David. To be honest,
>> I didn't know how to answer this question before. Actually this
>> question has puzzled me for a long time when dealing with memory
>> hot-removal. For normal cases, it only causes sub-optimal memory
>> allocation if schedule event happens between querying NUMA node id
>> and calling alloc_pages_node(). But what happens if system run into
>> following execution sequence?
>> 1) node = numa_mem_id();
>> 2) memory hot-removal event triggers
>> 2.1) remove affected memory
>> 2.2) reset pgdat to zero if node becomes empty after memory removal
> 
> I'm sorry if I misunderstand something.
> After commit b0dc3a342af36f95a68fe229b8f0f73552c5ca08, there is no
> memset().
Hi Kamezawa,
	Thanks for the information. The commit solved the issue what
I was puzzling about. With this change applied, thing should work
as expected. Seems it would be better to enhance __build_all_zonelists()
to handle those offlined empty nodes too, but that really doesn't
make to much difference:)
	Thanks for the info again!
Thanks!
Gerry

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