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author | yangge <yangge1116@126.com> | 2024-06-20 08:59:50 +0800 |
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committer | Andrew Morton <akpm@linux-foundation.org> | 2024-06-24 20:52:11 -0700 |
commit | bf14ed81f571f8dba31cd72ab2e50fbcc877cc31 (patch) | |
tree | 19608d8a2a14995b245f0565a1b8030bfde252ab /arch/arm64/boot/dts | |
parent | 54e7d59841dab977f6cb1183d658b1b82c9f4e94 (diff) | |
download | linux-stable-bf14ed81f571f8dba31cd72ab2e50fbcc877cc31.tar.gz linux-stable-bf14ed81f571f8dba31cd72ab2e50fbcc877cc31.tar.bz2 linux-stable-bf14ed81f571f8dba31cd72ab2e50fbcc877cc31.zip |
mm/page_alloc: Separate THP PCP into movable and non-movable categories
Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for
THP-sized allocations") no longer differentiates the migration type of
pages in THP-sized PCP list, it's possible that non-movable allocation
requests may get a CMA page from the list, in some cases, it's not
acceptable.
If a large number of CMA memory are configured in system (for example, the
CMA memory accounts for 50% of the system memory), starting a virtual
machine with device passthrough will get stuck. During starting the
virtual machine, it will call pin_user_pages_remote(..., FOLL_LONGTERM,
...) to pin memory. Normally if a page is present and in CMA area,
pin_user_pages_remote() will migrate the page from CMA area to non-CMA
area because of FOLL_LONGTERM flag. But if non-movable allocation
requests return CMA memory, migrate_longterm_unpinnable_pages() will
migrate a CMA page to another CMA page, which will fail to pass the check
in check_and_migrate_movable_pages() and cause migration endless.
Call trace:
pin_user_pages_remote
--__gup_longterm_locked // endless loops in this function
----_get_user_pages_locked
----check_and_migrate_movable_pages
------migrate_longterm_unpinnable_pages
--------alloc_migration_target
This problem will also have a negative impact on CMA itself. For example,
when CMA is borrowed by THP, and we need to reclaim it through cma_alloc()
or dma_alloc_coherent(), we must move those pages out to ensure CMA's
users can retrieve that contigous memory. Currently, CMA's memory is
occupied by non-movable pages, meaning we can't relocate them. As a
result, cma_alloc() is more likely to fail.
To fix the problem above, we add one PCP list for THP, which will not
introduce a new cacheline for struct per_cpu_pages. THP will have 2 PCP
lists, one PCP list is used by MOVABLE allocation, and the other PCP list
is used by UNMOVABLE allocation. MOVABLE allocation contains GPF_MOVABLE,
and UNMOVABLE allocation contains GFP_UNMOVABLE and GFP_RECLAIMABLE.
Link: https://lkml.kernel.org/r/1718845190-4456-1-git-send-email-yangge1116@126.com
Fixes: 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations")
Signed-off-by: yangge <yangge1116@126.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'arch/arm64/boot/dts')
0 files changed, 0 insertions, 0 deletions