Re: [PATCH v4 1/2] mm: introduce page reference manipulation functions
From: Vlastimil Babka
Date: Wed Mar 02 2016 - 11:44:25 EST
On 02/26/2016 01:58 AM, js1304@xxxxxxxxx wrote:
From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Success of CMA allocation largely depends on success of migration
and key factor of it is page reference count. Until now, page reference
is manipulated by direct calling atomic functions so we cannot follow up
who and where manipulate it. Then, it is hard to find actual reason
of CMA allocation failure. CMA allocation should be guaranteed to succeed
so finding offending place is really important.
In this patch, call sites where page reference is manipulated are converted
to introduced wrapper function. This is preparation step to add tracepoint
to each page reference manipulation function. With this facility, we can
easily find reason of CMA allocation failure. There is no functional change
in this patch.
In addition, this patch also converts reference read sites. It will help
a second step that renames page._count to something else and prevents later
attempt to direct access to it (Suggested by Andrew).
Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Even without Patch 2/2 this is a nice improvement.
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Although somebody might be confused by page_ref_count() vs page_count().
Oh well.