e12acd3eef
For CMA allocation, it's really critical to migrate a page but sometimes it fails. One of the reasons is some driver holds a page refcount for a long time so VM couldn't migrate the page at that time. The concern here is there is no way to find the who hold the refcount of the page effectively. This patch introduces feature to keep tracking page's pinner. All get_page sites are vulnerable to pin a page for a long time but the cost to keep track it would be significat since get_page is the most frequent kernel operation. Furthermore, the page could be not user page but kernel page which is not related to the page migration failure. Thus, this patch keeps tracks of only migration failed pages to reduce runtime cost. Once page migration fails in CMA allocation path, those pages are marked as "migration failure" and every put_page operation against those pages, callstack of the put are recorded into page_pinner buffer. Later, admin can see what pages were failed and who released the refcount since the failure. It really helps effectively to find out longtime refcount holder to prevent the page migration. note: page_pinner doesn't guarantee attributing/unattributing are atomic if they happen at the same time. It's just best effort so false-positive could happen. Bug: 183414571 BUg: 240196534 Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Minchan Kim <minchan@google.com> Change-Id: I603d0c0122734c377db6b1eb95848a6f734173a0 (cherry picked from commit 898cfbf094a2fc13c67fab5b5d3c916f0139833a)
6.4 KiB
6.4 KiB