Re: [PATCH] drm/radeon: adjust default radeon_vm_block_size

[Grigori Goronzy <greg@chown.ath.cx>]

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On 18.07.2014 11:38, Christian König wrote:
> From: Christian König <christian.koenig@amd.com>
> 
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
>  drivers/gpu/drm/radeon/radeon_device.c | 6 +++++-
>  drivers/gpu/drm/radeon/radeon_drv.c    | 4 ++--
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
> index 03686fa..a2960db 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1077,7 +1077,11 @@ static void radeon_check_arguments(struct radeon_device *rdev)
>  	/* defines number of bits in page table versus page directory,
>  	 * a page is 4KB so we have 12 bits offset, minimum 9 bits in the
>  	 * page table and the remaining bits are in the page directory */
> -	if (radeon_vm_block_size < 9) {
> +	if (radeon_vm_block_size == -1) {
> +		radeon_vm_block_size = (ilog2(radeon_vm_size) + 10) / 2;
> +		radeon_vm_block_size = max(radeon_vm_block_size, 9);
> +
> +	} else if (radeon_vm_block_size < 9) {

Hm, that automatic calculation seems strange. Is there any particular
reason why you haven chosen this? This will use vm_block_size=11 for
4096 MB VM space. I have used vm_block_size=12 with good results. This
manages 16 MB of VM space per page table, which seems reasonable. I also
see a noticeable CPU overhead reduction between 11 and 12.

Grigori

>  		dev_warn(rdev->dev, "VM page table size (%d) to small\n",
>  			 radeon_vm_block_size);
>  		radeon_vm_block_size = 9;
> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
> index cb14213..fef5320 100644
> --- a/drivers/gpu/drm/radeon/radeon_drv.c
> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
> @@ -174,7 +174,7 @@ int radeon_aspm = -1;
>  int radeon_runtime_pm = -1;
>  int radeon_hard_reset = 0;
>  int radeon_vm_size = 4096;
> -int radeon_vm_block_size = 9;
> +int radeon_vm_block_size = -1;
>  int radeon_deep_color = 0;
>  
>  MODULE_PARM_DESC(no_wb, "Disable AGP writeback for scratch registers");
> @@ -246,7 +246,7 @@ module_param_named(hard_reset, radeon_hard_reset, int, 0444);
>  MODULE_PARM_DESC(vm_size, "VM address space size in megabytes (default 4GB)");
>  module_param_named(vm_size, radeon_vm_size, int, 0444);
>  
> -MODULE_PARM_DESC(vm_block_size, "VM page table size in bits (default 9)");
> +MODULE_PARM_DESC(vm_block_size, "VM page table size in bits (default depending on vm_size)");
>  module_param_named(vm_block_size, radeon_vm_block_size, int, 0444);
>  
>  MODULE_PARM_DESC(deep_color, "Deep Color support (1 = enable, 0 = disable (default))");
> 



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