lkml.org 
[lkml]   [2021]   [Feb]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] mm: cma: support sysfs
From
Date
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@kernel.org>
> ---
> 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@kernel.org>
> +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@kernel.org>
> +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@kernel.org>
> +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@kernel.org>
> +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@kernel.org>
> +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

\
 
 \ /
  Last update: 2021-02-04 09:53    [W:0.130 / U:0.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site