[igt-dev] [PATCH i-g-t v5 11/15] lib/intel_allocator: treat default_alignment as the minimum

[Zbigniew Kempczyński]

On Fri, Oct 20, 2023 at 10:37:57AM +0100, Matthew Auld wrote:
> If something overrides the default alignment, we should only apply the
> alignment if it is larger than the default_alignment.
> 
> v2 (Niranjana):
>   - Simplify slightly
> 
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
> Cc: José Roberto de Souza <jose.souza at intel.com>
> Cc: Pallavi Mishra <pallavi.mishra at intel.com>
> Reviewed-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
> ---
>  lib/intel_allocator.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/intel_allocator.c b/lib/intel_allocator.c
> index e5b9457b8..96ffe40d5 100644
> --- a/lib/intel_allocator.c
> +++ b/lib/intel_allocator.c
> @@ -584,8 +584,8 @@ static int handle_request(struct alloc_req *req, struct alloc_resp *resp)
>  			break;
>  
>  		case REQ_ALLOC:
> -			if (!req->alloc.alignment)
> -				req->alloc.alignment = ial->default_alignment;
> +			req->alloc.alignment = max(ial->default_alignment,
> +						   req->alloc.alignment);

It will work but change current allocator behavior regarding
requested smaller alignment than default. I mean if allocator was
created with (let's say) 64K alignment and we want to suballocate
with 4K we can't do that with above code. All object regardless
our alignment requirement will be aligned to 64K.

Of course my need to have objects aligned to 4K is still reachable
if I create allocator with 4K as enforced alignment and pass 64K
as alignment argument on alloc().

What case are you solving with above code?

--
Zbigniew

>  
>  			resp->response_type = RESP_ALLOC;
>  			resp->alloc.offset = ial->alloc(ial,
> -- 
> 2.41.0
>