Re: [PATCH v3 13/35] lib: add allocation tagging support for memory allocation profiling

[Vlastimil Babka]

On 2/12/24 22:38, Suren Baghdasaryan wrote:
> Introduce CONFIG_MEM_ALLOC_PROFILING which provides definitions to easily
> instrument memory allocators. It registers an "alloc_tags" codetag type
> with /proc/allocinfo interface to output allocation tag information when
> the feature is enabled.
> CONFIG_MEM_ALLOC_PROFILING_DEBUG is provided for debugging the memory
> allocation profiling instrumentation.
> Memory allocation profiling can be enabled or disabled at runtime using
> /proc/sys/vm/mem_profiling sysctl when CONFIG_MEM_ALLOC_PROFILING_DEBUG=n.
> CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT enables memory allocation
> profiling by default.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Co-developed-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> ---
>  Documentation/admin-guide/sysctl/vm.rst |  16 +++
>  Documentation/filesystems/proc.rst      |  28 +++++
>  include/asm-generic/codetag.lds.h       |  14 +++
>  include/asm-generic/vmlinux.lds.h       |   3 +
>  include/linux/alloc_tag.h               | 133 ++++++++++++++++++++
>  include/linux/sched.h                   |  24 ++++
>  lib/Kconfig.debug                       |  25 ++++
>  lib/Makefile                            |   2 +
>  lib/alloc_tag.c                         | 158 ++++++++++++++++++++++++
>  scripts/module.lds.S                    |   7 ++
>  10 files changed, 410 insertions(+)
>  create mode 100644 include/asm-generic/codetag.lds.h
>  create mode 100644 include/linux/alloc_tag.h
>  create mode 100644 lib/alloc_tag.c
> 
> diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
> index c59889de122b..a214719492ea 100644
> --- a/Documentation/admin-guide/sysctl/vm.rst
> +++ b/Documentation/admin-guide/sysctl/vm.rst
> @@ -43,6 +43,7 @@ Currently, these files are in /proc/sys/vm:
>  - legacy_va_layout
>  - lowmem_reserve_ratio
>  - max_map_count
> +- mem_profiling         (only if CONFIG_MEM_ALLOC_PROFILING=y)
>  - memory_failure_early_kill
>  - memory_failure_recovery
>  - min_free_kbytes
> @@ -425,6 +426,21 @@ e.g., up to one or two maps per allocation.
>  The default value is 65530.
>  
>  
> +mem_profiling
> +==============
> +
> +Enable memory profiling (when CONFIG_MEM_ALLOC_PROFILING=y)
> +
> +1: Enable memory profiling.
> +
> +0: Disabld memory profiling.

      Disable

..

> +allocinfo
> +~~~~~~~
> +
> +Provides information about memory allocations at all locations in the code
> +base. Each allocation in the code is identified by its source file, line
> +number, module and the function calling the allocation. The number of bytes
> +allocated at each location is reported.

See, it even says "number of bytes" :)

> +
> +Example output.
> +
> +::
> +
> +    > cat /proc/allocinfo
> +
> +      153MiB     mm/slub.c:1826 module:slub func:alloc_slab_page

Is "module" meant in the usual kernel module sense? In that case IIRC is
more common to annotate things e.g. [xfs] in case it's really a module, and
nothing if it's built it, such as slub. Is that "slub" simply derived from
"mm/slub.c"? Then it's just redundant?

> +     6.08MiB     mm/slab_common.c:950 module:slab_common func:_kmalloc_order
> +     5.09MiB     mm/memcontrol.c:2814 module:memcontrol func:alloc_slab_obj_exts
> +     4.54MiB     mm/page_alloc.c:5777 module:page_alloc func:alloc_pages_exact
> +     1.32MiB     include/asm-generic/pgalloc.h:63 module:pgtable func:__pte_alloc_one
> +     1.16MiB     fs/xfs/xfs_log_priv.h:700 module:xfs func:xlog_kvmalloc
> +     1.00MiB     mm/swap_cgroup.c:48 module:swap_cgroup func:swap_cgroup_prepare
> +      734KiB     fs/xfs/kmem.c:20 module:xfs func:kmem_alloc
> +      640KiB     kernel/rcu/tree.c:3184 module:tree func:fill_page_cache_func
> +      640KiB     drivers/char/virtio_console.c:452 module:virtio_console func:alloc_buf
> +      ...
> +
> +
>  meminfo

..

> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 0be2d00c3696..78d258ca508f 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -972,6 +972,31 @@ config CODE_TAGGING
>  	bool
>  	select KALLSYMS
>  
> +config MEM_ALLOC_PROFILING
> +	bool "Enable memory allocation profiling"
> +	default n
> +	depends on PROC_FS
> +	depends on !DEBUG_FORCE_WEAK_PER_CPU
> +	select CODE_TAGGING
> +	help
> +	  Track allocation source code and record total allocation size
> +	  initiated at that code location. The mechanism can be used to track
> +	  memory leaks with a low performance and memory impact.
> +
> +config MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT
> +	bool "Enable memory allocation profiling by default"
> +	default y

I'd go with default n as that I'd select for a general distro.

> +	depends on MEM_ALLOC_PROFILING
> +
> +config MEM_ALLOC_PROFILING_DEBUG
> +	bool "Memory allocation profiler debugging"
> +	default n
> +	depends on MEM_ALLOC_PROFILING
> +	select MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT
> +	help
> +	  Adds warnings with helpful error messages for memory allocation
> +	  profiling.
> +