On 10/26/2016 06:31 AM, Joonsoo Kim wrote:
Hello, Here comes fixed one. ----------->8------------ From 93fb05a83d74f9e2c8caebc2fa6d1a8807c9ffb6 Mon Sep 17 00:00:00 2001 From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Date: Thu, 24 Mar 2016 22:29:10 +0900 Subject: [PATCH] mm/cma: populate ZONE_CMA Until now, reserved pages for CMA are managed in the ordinary zones where page's pfn are belong to. This approach has numorous problems and fixing them isn't easy. (It is mentioned on previous patch.) To fix this situation, ZONE_CMA is introduced in previous patch, but, not yet populated. This patch implement population of ZONE_CMA by stealing reserved pages from the ordinary zones. Unlike previous implementation that kernel allocation request with __GFP_MOVABLE could be serviced from CMA region, allocation request only with GFP_HIGHUSER_MOVABLE can be serviced from CMA region in the new approach. This is an inevitable design decision to use the zone implementation because ZONE_CMA could contain highmem. Due to this decision, ZONE_CMA will work like as ZONE_HIGHMEM or ZONE_MOVABLE. I don't think it would be a problem because most of file cache pages and anonymous pages are requested with GFP_HIGHUSER_MOVABLE. It could be proved by the fact that there are many systems with ZONE_HIGHMEM and they work fine. Notable disadvantage is that we cannot use these pages for blockdev file cache page, because it usually has __GFP_MOVABLE but not __GFP_HIGHMEM and __GFP_USER. But, in this case, there is pros and cons. In my experience, blockdev file cache pages are one of the top reason that causes cma_alloc() to fail temporarily. So, we can get more guarantee of cma_alloc() success by discarding that case. Implementation itself is very easy to understand. Steal when cma area is initialized and recalculate various per zone stat/threshold. Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
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