[PATCH 1/3] drm/ttm: set sensible pool size limit.

Michel Dänzer michel at daenzer.net
Tue Aug 12 23:24:40 PDT 2014

On 13.08.2014 12:52, Jérôme Glisse wrote:
> From: Jérôme Glisse <jglisse at redhat.com>
> Due to bug in code it appear that some of the pool where never properly
> use and always empty. Before fixing that bug this patch set sensible
> limit on pool size. The magic 64MB number was nominated.
> This is obviously a some what arbitrary number but the intend of ttm pool
> is to minimize page alloc cost especialy when allocating page that will be
> mark to be excluded from cpu cache mecanisms. We assume that mostly small
> buffer that are constantly allocated/deallocated might suffer from core
> memory allocation overhead as well as cache status change. This are the
> assumptions behind the 64MB value.
> This obviously need some serious testing including monitoring pool size.
> Signed-off-by: Jérôme Glisse <jglisse at redhat.com>


> @@ -393,8 +404,9 @@ int ttm_mem_global_init(struct ttm_mem_global *glob)
>  		pr_info("Zone %7s: Available graphics memory: %llu kiB\n",
>  			zone->name, (unsigned long long)zone->max_mem >> 10);
>  	}
> -	ttm_page_alloc_init(glob, glob->zone_kernel->max_mem/(2*PAGE_SIZE));
> -	ttm_dma_page_alloc_init(glob, glob->zone_kernel->max_mem/(2*PAGE_SIZE));
> +	max_pool_size = min(glob->zone_kernel->max_mem >> 3UL, MAX_POOL_SIZE);

This introduces a 'comparison of distinct pointer types lacks a cast'
warning for me.

Earthling Michel Dänzer            |                  http://www.amd.com
Libre software enthusiast          |                Mesa and X developer

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