On 2/3/21 7:50 AM, Minchan Kim wrote:
Since CMA is getting used more widely, it's more important to
keep monitoring CMA statistics for system health since it's
directly related to user experience.
This patch introduces sysfs for the CMA and exposes stats below
to keep monitor for telemetric in the system.
* the number of CMA allocation attempts
* the number of CMA allocation failures
* the number of CMA page allocation attempts
* the number of CMA page allocation failures
The desire to report CMA data is understandable, but there are a few
odd things here:
1) First of all, this has significant overlap with /sys/kernel/debug/cma
items. I suspect that all of these items could instead go into
/sys/kernel/debug/cma, right?
2) The overall CMA allocation attempts/failures (first two items above) seem
an odd pair of things to track. Maybe that is what was easy to track, but I'd
vote for just omitting them.
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-kernel-mm-cma | 39 +++++
include/linux/cma.h | 1 +
mm/Makefile | 1 +
mm/cma.c | 6 +-
mm/cma.h | 20 +++
mm/cma_sysfs.c | 143 ++++++++++++++++++
6 files changed, 209 insertions(+), 1 deletion(-)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-cma
create mode 100644 mm/cma_sysfs.c
diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-cma b/Documentation/ABI/testing/sysfs-kernel-mm-cma
new file mode 100644
index 000000000000..2a43c0aacc39
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-cma
@@ -0,0 +1,39 @@
+What: /sys/kernel/mm/cma/
+Date: Feb 2021
+Contact: Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+ /sys/kernel/mm/cma/ contains a number of subdirectories by
+ cma-heap name. The subdirectory contains a number of files
+ to represent cma allocation statistics.
Somewhere, maybe here, there should be a mention of the closely related
/sys/kernel/debug/cma files.
+
+ There are number of files under
+ /sys/kernel/mm/cma/<cma-heap-name> directory
+
+ - cma_alloc_attempt
+ - cma_alloc_fail
Are these really useful? They a summary of the alloc_pages items, really.
+ - alloc_pages_attempt
+ - alloc_pages_fail
This should also have "cma" in the name, really: cma_alloc_pages_*.
+
+What: /sys/kernel/mm/cma/<cma-heap-name>/cma_alloc_attempt
+Date: Feb 2021
+Contact: Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+ the number of cma_alloc API attempted
+
+What: /sys/kernel/mm/cma/<cma-heap-name>/cma_alloc_fail
+Date: Feb 2021
+Contact: Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+ the number of CMA_alloc API failed
+
+What: /sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_attempt
+Date: Feb 2021
+Contact: Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+ the number of pages CMA API tried to allocate
+
+What: /sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_fail
+Date: Feb 2021
+Contact: Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+ the number of pages CMA API failed to allocate
diff --git a/include/linux/cma.h b/include/linux/cma.h
index 217999c8a762..71a28a5bb54e 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h
@@ -49,4 +49,5 @@ extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count);
extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data);
+
A single additional blank line seems to be the only change to this file. :)
thanks,
--
John Hubbard
NVIDIA
