Re: [PATCH] staging: android: ion: Add requested allocation alignment

[Alexey Skidanov]

On 02/12/2018 10:46 PM, Laura Abbott wrote:
> On 02/12/2018 12:22 PM, Alexey Skidanov wrote:
>>
>>
>> On 02/12/2018 09:52 PM, Laura Abbott wrote:
>>> On 02/12/2018 11:11 AM, Alexey Skidanov wrote:

 On 02/12/2018 08:42 PM, Laura Abbott wrote:
> On 02/10/2018 02:17 AM, Alexey Skidanov wrote:
>> Current ion defined allocation ioctl doesn't allow to specify the
>> requested
>> allocation alignment. CMA heap allocates buffers aligned on buffer
>> size
>> page order.
>>
>> Sometimes, the alignment requirement is less restrictive. In such
>> cases,
>> providing specific alignment may reduce the external memory
>> fragmentation
>> and in some cases it may avoid the allocation request failure.
>>
> I really do not want to bring this back as part of the regular
> ABI.
 Yes, I know it was removed in 4.12.
 Having an alignment parameter that gets used for exactly
> one heap only leads to confusion (which is why it was removed
> from the ABI in the first place).
 You are correct regarding the CMA heap. But, probably it may be used by
 custom heap as well.
>>>
>>> I can think of a lot of instances where it could be used but
>>> ultimately there needs to be an actual in kernel user who wants
>>> it.
>>>
> The alignment came from the behavior of the DMA APIs. Do you
> actually need to specify any alignment from userspace or do
> you only need page size?
 Yes. If CMA gives it for free, I would suggest to let the ion user to
 decide
>>>
>>> I'm really not convinced changing the ABI yet again just to let
>>> the user decide is actually worth it. If we can manage it, I'd
>>> much rather see a proposal that doesn't change the ABI.
>> I didn't actually change the ABI - I just use the "unused" member:
>> struct ion_allocation_data {
>> @@ -80,7 +79,7 @@ struct ion_allocation_data {
>>  __u32 heap_id_mask;
>>  __u32 flags;
>>  __u32 fd;
>> -   __u32 unused;
>> +   __u32 align;
>>   };
>>
> 
> Something that was previously unused is now being used. That's a change
> in how the structure is interpreted which is an ABI change, especially
> since we haven't been checking that the __unused field is set
> to 0.
Yes you are correct. I just realized that it isn't even backward
compatible.
> 
>> As an alternative, I may add __u64 heap_specific_param - but this will
>> change the ABI. But, probably it makes the ABI more generic?
> 
> Why does the ABI need to be more generic? If we change the ABI
> we're stuck with it and I'd like to approach it as the very last
> resort.
> 
> Thanks,
> Laura
It seems, that there is no way to do it without some ABI change?

Thanks,
Alexey
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Re: [PATCH] staging: android: ion: Add requested allocation alignment

[Laura Abbott]

On 02/12/2018 12:22 PM, Alexey Skidanov wrote:



On 02/12/2018 09:52 PM, Laura Abbott wrote:

On 02/12/2018 11:11 AM, Alexey Skidanov wrote:


On 02/12/2018 08:42 PM, Laura Abbott wrote:

On 02/10/2018 02:17 AM, Alexey Skidanov wrote:

Current ion defined allocation ioctl doesn't allow to specify the
requested
allocation alignment. CMA heap allocates buffers aligned on buffer size
page order.

Sometimes, the alignment requirement is less restrictive. In such
cases,
providing specific alignment may reduce the external memory
fragmentation
and in some cases it may avoid the allocation request failure.


I really do not want to bring this back as part of the regular
ABI.

Yes, I know it was removed in 4.12.
Having an alignment parameter that gets used for exactly

one heap only leads to confusion (which is why it was removed
from the ABI in the first place).

You are correct regarding the CMA heap. But, probably it may be used by
custom heap as well.


I can think of a lot of instances where it could be used but
ultimately there needs to be an actual in kernel user who wants
it.


The alignment came from the behavior of the DMA APIs. Do you
actually need to specify any alignment from userspace or do
you only need page size?

Yes. If CMA gives it for free, I would suggest to let the ion user to
decide


I'm really not convinced changing the ABI yet again just to let
the user decide is actually worth it. If we can manage it, I'd
much rather see a proposal that doesn't change the ABI.

I didn't actually change the ABI - I just use the "unused" member:
struct ion_allocation_data {
@@ -80,7 +79,7 @@ struct ion_allocation_data {
 __u32 heap_id_mask;
 __u32 flags;
 __u32 fd;
-   __u32 unused;
+   __u32 align;
  };



Something that was previously unused is now being used. That's a change
in how the structure is interpreted which is an ABI change, especially
since we haven't been checking that the __unused field is set
to 0.


As an alternative, I may add __u64 heap_specific_param - but this will
change the ABI. But, probably it makes the ABI more generic?


Why does the ABI need to be more generic? If we change the ABI
we're stuck with it and I'd like to approach it as the very last
resort.

Thanks,
Laura
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Re: [PATCH] staging: android: ion: Add requested allocation alignment

[Alexey Skidanov]

On 02/12/2018 09:52 PM, Laura Abbott wrote:
> On 02/12/2018 11:11 AM, Alexey Skidanov wrote:
>>
>> On 02/12/2018 08:42 PM, Laura Abbott wrote:
>>> On 02/10/2018 02:17 AM, Alexey Skidanov wrote:
 Current ion defined allocation ioctl doesn't allow to specify the
 requested
 allocation alignment. CMA heap allocates buffers aligned on buffer size
 page order.

 Sometimes, the alignment requirement is less restrictive. In such
 cases,
 providing specific alignment may reduce the external memory
 fragmentation
 and in some cases it may avoid the allocation request failure.

>>> I really do not want to bring this back as part of the regular
>>> ABI.
>> Yes, I know it was removed in 4.12.
>> Having an alignment parameter that gets used for exactly
>>> one heap only leads to confusion (which is why it was removed
>>> from the ABI in the first place).
>> You are correct regarding the CMA heap. But, probably it may be used by
>> custom heap as well.
> 
> I can think of a lot of instances where it could be used but
> ultimately there needs to be an actual in kernel user who wants
> it.
> 
>>> The alignment came from the behavior of the DMA APIs. Do you
>>> actually need to specify any alignment from userspace or do
>>> you only need page size?
>> Yes. If CMA gives it for free, I would suggest to let the ion user to
>> decide
> 
> I'm really not convinced changing the ABI yet again just to let
> the user decide is actually worth it. If we can manage it, I'd
> much rather see a proposal that doesn't change the ABI.
I didn't actually change the ABI - I just use the "unused" member:
struct ion_allocation_data {
@@ -80,7 +79,7 @@ struct ion_allocation_data {
__u32 heap_id_mask;
__u32 flags;
__u32 fd;
-   __u32 unused;
+   __u32 align;
 };

As an alternative, I may add __u64 heap_specific_param - but this will
change the ABI. But, probably it makes the ABI more generic?
> 
>>> Thanks,
>>> Laura
>>>
>> Thanks,
>> Alexey
>>
> 

Thanks,
Alexey
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Re: [PATCH] staging: android: ion: Add requested allocation alignment

[Laura Abbott]

On 02/12/2018 11:11 AM, Alexey Skidanov wrote:


On 02/12/2018 08:42 PM, Laura Abbott wrote:

On 02/10/2018 02:17 AM, Alexey Skidanov wrote:

Current ion defined allocation ioctl doesn't allow to specify the
requested
allocation alignment. CMA heap allocates buffers aligned on buffer size
page order.

Sometimes, the alignment requirement is less restrictive. In such cases,
providing specific alignment may reduce the external memory fragmentation
and in some cases it may avoid the allocation request failure.


I really do not want to bring this back as part of the regular
ABI.

Yes, I know it was removed in 4.12.
Having an alignment parameter that gets used for exactly

one heap only leads to confusion (which is why it was removed
from the ABI in the first place).

You are correct regarding the CMA heap. But, probably it may be used by
custom heap as well.


I can think of a lot of instances where it could be used but
ultimately there needs to be an actual in kernel user who wants
it.


The alignment came from the behavior of the DMA APIs. Do you
actually need to specify any alignment from userspace or do
you only need page size?

Yes. If CMA gives it for free, I would suggest to let the ion user to decide


I'm really not convinced changing the ABI yet again just to let
the user decide is actually worth it. If we can manage it, I'd
much rather see a proposal that doesn't change the ABI.


Thanks,
Laura


Thanks,
Alexey



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Re: [PATCH] staging: android: ion: Add requested allocation alignment

[Alexey Skidanov]

On 02/12/2018 08:42 PM, Laura Abbott wrote:
> On 02/10/2018 02:17 AM, Alexey Skidanov wrote:
>> Current ion defined allocation ioctl doesn't allow to specify the
>> requested
>> allocation alignment. CMA heap allocates buffers aligned on buffer size
>> page order.
>>
>> Sometimes, the alignment requirement is less restrictive. In such cases,
>> providing specific alignment may reduce the external memory fragmentation
>> and in some cases it may avoid the allocation request failure.
>>
> 
> I really do not want to bring this back as part of the regular
> ABI. 
Yes, I know it was removed in 4.12.
Having an alignment parameter that gets used for exactly
> one heap only leads to confusion (which is why it was removed
> from the ABI in the first place).
You are correct regarding the CMA heap. But, probably it may be used by
custom heap as well.
> 
> The alignment came from the behavior of the DMA APIs. Do you
> actually need to specify any alignment from userspace or do
> you only need page size?
Yes. If CMA gives it for free, I would suggest to let the ion user to decide
> 
> Thanks,
> Laura
> 
Thanks,
Alexey

>> To fix this, we add an alignment parameter to the allocation ioctl.
>>
>> Signed-off-by: Alexey Skidanov 
>> ---
>>   drivers/staging/android/ion/ion-ioctl.c |  3 ++-
>>   drivers/staging/android/ion/ion.c   | 14 +-
>>   drivers/staging/android/ion/ion.h   |  9 ++---
>>   drivers/staging/android/ion/ion_carveout_heap.c |  3 ++-
>>   drivers/staging/android/ion/ion_chunk_heap.c    |  3 ++-
>>   drivers/staging/android/ion/ion_cma_heap.c  | 18 --
>>   drivers/staging/android/ion/ion_system_heap.c   |  6 --
>>   drivers/staging/android/uapi/ion.h  |  7 +++
>>   8 files changed, 40 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/staging/android/ion/ion-ioctl.c
>> b/drivers/staging/android/ion/ion-ioctl.c
>> index c789893..9fe022b 100644
>> --- a/drivers/staging/android/ion/ion-ioctl.c
>> +++ b/drivers/staging/android/ion/ion-ioctl.c
>> @@ -83,7 +83,8 @@ long ion_ioctl(struct file *filp, unsigned int cmd,
>> unsigned long arg)
>>     fd = ion_alloc(data.allocation.len,
>>  data.allocation.heap_id_mask,
>> -   data.allocation.flags);
>> +   data.allocation.flags,
>> +   data.allocation.align);
>>   if (fd < 0)
>>   return fd;
>>   diff --git a/drivers/staging/android/ion/ion.c
>> b/drivers/staging/android/ion/ion.c
>> index f480885..35ddc7a 100644
>> --- a/drivers/staging/android/ion/ion.c
>> +++ b/drivers/staging/android/ion/ion.c
>> @@ -78,7 +78,8 @@ static void ion_buffer_add(struct ion_device *dev,
>>   static struct ion_buffer *ion_buffer_create(struct ion_heap *heap,
>>   struct ion_device *dev,
>>   unsigned long len,
>> -    unsigned long flags)
>> +    unsigned long flags,
>> +    unsigned int align)
>>   {
>>   struct ion_buffer *buffer;
>>   int ret;
>> @@ -90,14 +91,14 @@ static struct ion_buffer *ion_buffer_create(struct
>> ion_heap *heap,
>>   buffer->heap = heap;
>>   buffer->flags = flags;
>>   -    ret = heap->ops->allocate(heap, buffer, len, flags);
>> +    ret = heap->ops->allocate(heap, buffer, len, flags, align);
>>     if (ret) {
>>   if (!(heap->flags & ION_HEAP_FLAG_DEFER_FREE))
>>   goto err2;
>>     ion_heap_freelist_drain(heap, 0);
>> -    ret = heap->ops->allocate(heap, buffer, len, flags);
>> +    ret = heap->ops->allocate(heap, buffer, len, flags, align);
>>   if (ret)
>>   goto err2;
>>   }
>> @@ -390,7 +391,10 @@ static const struct dma_buf_ops dma_buf_ops = {
>>   .unmap = ion_dma_buf_kunmap,
>>   };
>>   -int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int
>> flags)
>> +int ion_alloc(size_t len,
>> +  unsigned int heap_id_mask,
>> +  unsigned int flags,
>> +  unsigned int align)
>>   {
>>   struct ion_device *dev = internal_dev;
>>   struct ion_buffer *buffer = NULL;
>> @@ -417,7 +421,7 @@ int ion_alloc(size_t len, unsigned int
>> heap_id_mask, unsigned int flags)
>>   /* if the caller didn't specify this heap id */
>>   if (!((1 << heap->id) & heap_id_mask))
>>   continue;
>> -    buffer = ion_buffer_create(heap, dev, len, flags);
>> +    buffer = ion_buffer_create(heap, dev, len, flags, align);
>>   if (!IS_ERR(buffer))
>>   break;
>>   }
>> diff --git a/drivers/staging/android/ion/ion.h
>> b/drivers/staging/android/ion/ion.h
>> index f5f9cd6..0c161d2 100644
>> --- a/drivers/staging/android/ion/ion.h
>> +++ b/drivers/staging/android/ion/ion.h
>> @@ -123,8 +123,10 @@ struct ion_device {
>>    */
>>   struct ion_heap_ops {
>>   int (*allocate)(struct 

Re: [PATCH] staging: android: ion: Add requested allocation alignment

[Laura Abbott]

On 02/10/2018 02:17 AM, Alexey Skidanov wrote:

Current ion defined allocation ioctl doesn't allow to specify the requested
allocation alignment. CMA heap allocates buffers aligned on buffer size
page order.

Sometimes, the alignment requirement is less restrictive. In such cases,
providing specific alignment may reduce the external memory fragmentation
and in some cases it may avoid the allocation request failure.



I really do not want to bring this back as part of the regular
ABI. Having an alignment parameter that gets used for exactly
one heap only leads to confusion (which is why it was removed
from the ABI in the first place).

The alignment came from the behavior of the DMA APIs. Do you
actually need to specify any alignment from userspace or do
you only need page size?

Thanks,
Laura


To fix this, we add an alignment parameter to the allocation ioctl.

Signed-off-by: Alexey Skidanov 
---
  drivers/staging/android/ion/ion-ioctl.c |  3 ++-
  drivers/staging/android/ion/ion.c   | 14 +-
  drivers/staging/android/ion/ion.h   |  9 ++---
  drivers/staging/android/ion/ion_carveout_heap.c |  3 ++-
  drivers/staging/android/ion/ion_chunk_heap.c|  3 ++-
  drivers/staging/android/ion/ion_cma_heap.c  | 18 --
  drivers/staging/android/ion/ion_system_heap.c   |  6 --
  drivers/staging/android/uapi/ion.h  |  7 +++
  8 files changed, 40 insertions(+), 23 deletions(-)

diff --git a/drivers/staging/android/ion/ion-ioctl.c 
b/drivers/staging/android/ion/ion-ioctl.c
index c789893..9fe022b 100644
--- a/drivers/staging/android/ion/ion-ioctl.c
+++ b/drivers/staging/android/ion/ion-ioctl.c
@@ -83,7 +83,8 @@ long ion_ioctl(struct file *filp, unsigned int cmd, unsigned 
long arg)
  
  		fd = ion_alloc(data.allocation.len,

   data.allocation.heap_id_mask,
-  data.allocation.flags);
+  data.allocation.flags,
+  data.allocation.align);
if (fd < 0)
return fd;
  
diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c

index f480885..35ddc7a 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -78,7 +78,8 @@ static void ion_buffer_add(struct ion_device *dev,
  static struct ion_buffer *ion_buffer_create(struct ion_heap *heap,
struct ion_device *dev,
unsigned long len,
-   unsigned long flags)
+   unsigned long flags,
+   unsigned int align)
  {
struct ion_buffer *buffer;
int ret;
@@ -90,14 +91,14 @@ static struct ion_buffer *ion_buffer_create(struct ion_heap 
*heap,
buffer->heap = heap;
buffer->flags = flags;
  
-	ret = heap->ops->allocate(heap, buffer, len, flags);

+   ret = heap->ops->allocate(heap, buffer, len, flags, align);
  
  	if (ret) {

if (!(heap->flags & ION_HEAP_FLAG_DEFER_FREE))
goto err2;
  
  		ion_heap_freelist_drain(heap, 0);

-   ret = heap->ops->allocate(heap, buffer, len, flags);
+   ret = heap->ops->allocate(heap, buffer, len, flags, align);
if (ret)
goto err2;
}
@@ -390,7 +391,10 @@ static const struct dma_buf_ops dma_buf_ops = {
.unmap = ion_dma_buf_kunmap,
  };
  
-int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags)

+int ion_alloc(size_t len,
+ unsigned int heap_id_mask,
+ unsigned int flags,
+ unsigned int align)
  {
struct ion_device *dev = internal_dev;
struct ion_buffer *buffer = NULL;
@@ -417,7 +421,7 @@ int ion_alloc(size_t len, unsigned int heap_id_mask, 
unsigned int flags)
/* if the caller didn't specify this heap id */
if (!((1 << heap->id) & heap_id_mask))
continue;
-   buffer = ion_buffer_create(heap, dev, len, flags);
+   buffer = ion_buffer_create(heap, dev, len, flags, align);
if (!IS_ERR(buffer))
break;
}
diff --git a/drivers/staging/android/ion/ion.h 
b/drivers/staging/android/ion/ion.h
index f5f9cd6..0c161d2 100644
--- a/drivers/staging/android/ion/ion.h
+++ b/drivers/staging/android/ion/ion.h
@@ -123,8 +123,10 @@ struct ion_device {
   */
  struct ion_heap_ops {
int (*allocate)(struct ion_heap *heap,
-   struct ion_buffer *buffer, unsigned long len,
-   unsigned long flags);
+   struct ion_buffer *buffer,
+   unsigned long len,
+   unsigned long flags,
+   unsigned int