path: root/Documentation/DMA-API.txt
diff options
authorRobin Murphy <robin.murphy@arm.com>2018-12-10 14:00:30 (GMT)
committerChristoph Hellwig <hch@lst.de>2018-12-11 13:31:18 (GMT)
commitceb51173b2b5bd7af0d99079f6bbacdcfc58fe08 (patch)
treebc9245f7e98c8e07a1d203d143da808330c244fd /Documentation/DMA-API.txt
parent2b9d9ac02b9d8d32c515c82bb17401c429f160ab (diff)
dma-debug: Make leak-like behaviour apparent
Now that we can dynamically allocate DMA debug entries to cope with drivers maintaining excessively large numbers of live mappings, a driver which *does* actually have a bug leaking mappings (and is not unloaded) will no longer trigger the "DMA-API: debugging out of memory - disabling" message until it gets to actual kernel OOM conditions, which means it could go unnoticed for a while. To that end, let's inform the user each time the pool has grown to a multiple of its initial size, which should make it apparent that they either have a leak or might want to increase the preallocation size. Signed-off-by: Robin Murphy <robin.murphy@arm.com> Tested-by: Qian Cai <cai@lca.pw> Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'Documentation/DMA-API.txt')
1 files changed, 5 insertions, 1 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 0fcb756..7a7d8a4 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -747,7 +747,11 @@ driver afterwards. This filter can be disabled or changed later using debugfs.
When the code disables itself at runtime this is most likely because it ran
out of dma_debug_entries and was unable to allocate more on-demand. 65536
entries are preallocated at boot - if this is too low for you boot with
-'dma_debug_entries=<your_desired_number>' to overwrite the default.
+'dma_debug_entries=<your_desired_number>' to overwrite the default. The
+code will print to the kernel log each time it has dynamically allocated
+as many entries as were initially preallocated. This is to indicate that a
+larger preallocation size may be appropriate, or if it happens continually
+that a driver may be leaking mappings.