This patch series introduces the Page Alloc Hogger. The Page Alloc Hogger
allows you to allocate memory pages from specific nodes, zones, migration
types, and orders directly via debugfs. This provides key benefits for
testing and debugging:
- Reproduce low-memory conditions: Easily trigger and inspect kernel
mechanisms like direct reclaim, kswapd, the OOM killer, and allocation
fallbacks.
- Simplify memory pressure debugging: Debug issues that only manifest under
memory stress without needing custom kernel drivers or userspace programs
to allocate memory.
- Simplify unit testing: Verify that memory management subsystems
(direct reclaim, OOM killer, kswapd) trigger as expected in test suites.
- Measure performance under stress: Evaluate how applications behave and
perform during severe memory pressure.
Usage:
1. To trigger the allocation, navigate to the debugfs path corresponding
to your target node, memory zone, allocation order, and migration type,
then write the requested allocation count to nr_pages_allocs.
For example, to make 3 allocs of order 9, Migrate Type Movable,
Zone Normal and Node 0, run:
$ echo 3 > /sys/kernel/debug/mm/node-0/zone-Normal/order-9/migrate-Movable/nr_pages_allocs
2. For each allocation created, a corresponding file named sequentially
(1, 2, n) will appear in that directory.
$ ls /sys/kernel/debug/mm/node-0/zone-Normal/order-9/migrate-Movable/
1 2 3 nr_pages_allocs
3. To free the allocation, write the allocation file name in
/sys/kernel/debug/mm/free. For example, to release the 2nd allocation run:
$ echo 2 > /sys/kernel/debug/mm/free
Example:
$ cat /proc/pagetypeinfo
Page block order: 9
Pages per block: 512
Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
Node 0, zone DMA, type Unmovable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type Movable 1 1 1 0 1 1 2 2 1 3 732
Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type CMA 0 0 0 0 0 0 0 0 0 1 7
Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Unmovable 13 7 0 1 0 0 1 0 1 0 0
Node 0, zone Normal, type Movable 1 1 1 1 1 1 1 0 1 1 1221
Node 0, zone Normal, type Reclaimable 1 0 0 0 0 0 1 0 0 1 0
Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type CMA 0 0 0 0 0 0 0 0 0 1 7
Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Number of blocks type Unmovable Movable Reclaimable HighAtomic CMA Isolate
Node 0, zone DMA 0 1520 0 0 16 0
Node 0, zone Normal 12 2530 2 0 16 0
$ echo 1200 > /sys/kernel/debug/mm/node-0/zone-Normal/order-10/migrate-Movable/nr_pages_allocs
$ cat /proc/pagetypeinfo
Page block order: 9
Pages per block: 512
Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
Node 0, zone DMA, type Unmovable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type Movable 1 1 1 0 1 1 2 2 1 3 732
Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type CMA 0 0 0 0 0 0 0 0 0 1 7
Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Unmovable 13 7 1 1 0 0 0 0 1 0 0
Node 0, zone Normal, type Movable 1 1 1 1 1 1 1 0 1 1 21
Node 0, zone Normal, type Reclaimable 0 1 0 0 1 0 0 0 1 0 0
Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type CMA 0 0 0 0 0 0 0 0 0 1 7
Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Number of blocks type Unmovable Movable Reclaimable HighAtomic CMA Isolate
Node 0, zone DMA 0 1520 0 0 16 0
Node 0, zone Normal 12 2530 2 0 16 0
$ for i in `seq 1 1200`; do echo $i > /sys/kernel/debug/mm/free; done
$ cat /proc/pagetypeinfo
Page block order: 9
Pages per block: 512
Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
Node 0, zone DMA, type Unmovable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type Movable 1 1 1 0 1 1 2 2 1 3 732
Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type CMA 0 0 0 0 0 0 0 0 0 1 7
Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Unmovable 13 7 1 1 0 0 0 0 1 0 0
Node 0, zone Normal, type Movable 1 1 1 1 1 1 1 0 1 1 1221
Node 0, zone Normal, type Reclaimable 0 1 0 0 1 0 0 0 1 0 0
Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type CMA 0 0 0 0 0 0 0 0 0 1 7
Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Number of blocks type Unmovable Movable Reclaimable HighAtomic CMA Isolate
Node 0, zone DMA 0 1520 0 0 16 0
Node 0, zone Normal 12 2530 2 0 16 0
Notes:
- The only zone that is not supported is ZONE_DEVICE.
- MIGRATE_CMA will be supported soon
Juan Yescas (16):
mm: Page Alloc Hogger module
mm: Define structs for allocation requests and store allocations
mm: Define the caches for the structs req_alloc and page_alloc
mm: Define function to create a dir for each online node
mm: Define function to create a dir for populated zone
mm: Define function to create a dir for each page order
mm: Define function to create a dir for each migrate type
mm: Define function that creates the "nr_pages_allocs" file
mm: Read the nr_pages_allocs value given by user
mm: Set the selected zone in gfp_t flags
mm: Sets the migrate type in gfp_t flags
mm: Define the make_alloc() function
mm: Create the file asociated with an allocation
mm: Free pages, remove files and clean cache when one alloc fails
mm: Create the "free" file to release the previously allocated pages
mm: Release resources when the page alloc hogger module exits
mm/Kconfig.debug | 12 +
mm/Makefile | 1 +
mm/page_alloc_hogger.c | 611 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 624 insertions(+)
create mode 100644 mm/page_alloc_hogger.c
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2.55.0.229.g6434b31f56-goog