diff mbox series

[v3,20/35] lib: add codetag reference into slabobj_ext

Message ID 20240212213922.783301-21-surenb@google.com
State New
Headers
Series Memory allocation profiling |

Commit Message

Suren Baghdasaryan Feb. 12, 2024, 9:39 p.m. UTC 
  To store code tag for every slab object, a codetag reference is embedded
into slabobj_ext when CONFIG_MEM_ALLOC_PROFILING=y.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Co-developed-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 include/linux/memcontrol.h | 5 +++++
 lib/Kconfig.debug          | 1 +
 mm/slab.h                  | 4 ++++
 3 files changed, 10 insertions(+)

Comments

Vlastimil Babka Feb. 16, 2024, 3:36 p.m. UTC | #1 
On 2/12/24 22:39, Suren Baghdasaryan wrote:
> To store code tag for every slab object, a codetag reference is embedded
> into slabobj_ext when CONFIG_MEM_ALLOC_PROFILING=y.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> Co-developed-by: Kent Overstreet <kent.overstreet@linux.dev>
> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
> ---
>  include/linux/memcontrol.h | 5 +++++
>  lib/Kconfig.debug          | 1 +
>  mm/slab.h                  | 4 ++++
>  3 files changed, 10 insertions(+)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index f3584e98b640..2b010316016c 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1653,7 +1653,12 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
>   * if MEMCG_DATA_OBJEXTS is set.
>   */
>  struct slabobj_ext {
> +#ifdef CONFIG_MEMCG_KMEM
>  	struct obj_cgroup *objcg;
> +#endif
> +#ifdef CONFIG_MEM_ALLOC_PROFILING
> +	union codetag_ref ref;
> +#endif
>  } __aligned(8);

So this means that compiling with CONFIG_MEM_ALLOC_PROFILING will increase
the memory overhead of arrays allocated for CONFIG_MEMCG_KMEM, even if
allocation profiling itself is not enabled in runtime? Similar concern to
the unconditional page_ext usage, that this would hinder enabling in a
general distro kernel.

The unused field overhead would be smaller than currently page_ext, but
getting rid of it when alloc profiling is not enabled would be more work
than introducing an early boot param for the page_ext case. Could be however
solved similarly to how page_ext is populated dynamically at runtime.
Hopefully it wouldn't add noticeable cpu overhead.

>  static inline void __inc_lruvec_kmem_state(void *p, enum node_stat_item idx)
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 7bbdb0ddb011..9ecfcdb54417 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -979,6 +979,7 @@ config MEM_ALLOC_PROFILING
>  	depends on !DEBUG_FORCE_WEAK_PER_CPU
>  	select CODE_TAGGING
>  	select PAGE_EXTENSION
> +	select SLAB_OBJ_EXT
>  	help
>  	  Track allocation source code and record total allocation size
>  	  initiated at that code location. The mechanism can be used to track
> diff --git a/mm/slab.h b/mm/slab.h
> index 77cf7474fe46..224a4b2305fb 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -569,6 +569,10 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
>  
>  static inline bool need_slab_obj_ext(void)
>  {
> +#ifdef CONFIG_MEM_ALLOC_PROFILING
> +	if (mem_alloc_profiling_enabled())
> +		return true;
> +#endif
>  	/*
>  	 * CONFIG_MEMCG_KMEM creates vector of obj_cgroup objects conditionally
>  	 * inside memcg_slab_post_alloc_hook. No other users for now.
Suren Baghdasaryan Feb. 16, 2024, 5:04 p.m. UTC | #2 
On Fri, Feb 16, 2024 at 7:36 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 2/12/24 22:39, Suren Baghdasaryan wrote:
> > To store code tag for every slab object, a codetag reference is embedded
> > into slabobj_ext when CONFIG_MEM_ALLOC_PROFILING=y.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > Co-developed-by: Kent Overstreet <kent.overstreet@linux.dev>
> > Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
> > ---
> >  include/linux/memcontrol.h | 5 +++++
> >  lib/Kconfig.debug          | 1 +
> >  mm/slab.h                  | 4 ++++
> >  3 files changed, 10 insertions(+)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index f3584e98b640..2b010316016c 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -1653,7 +1653,12 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
> >   * if MEMCG_DATA_OBJEXTS is set.
> >   */
> >  struct slabobj_ext {
> > +#ifdef CONFIG_MEMCG_KMEM
> >       struct obj_cgroup *objcg;
> > +#endif
> > +#ifdef CONFIG_MEM_ALLOC_PROFILING
> > +     union codetag_ref ref;
> > +#endif
> >  } __aligned(8);
>
> So this means that compiling with CONFIG_MEM_ALLOC_PROFILING will increase
> the memory overhead of arrays allocated for CONFIG_MEMCG_KMEM, even if
> allocation profiling itself is not enabled in runtime? Similar concern to
> the unconditional page_ext usage, that this would hinder enabling in a
> general distro kernel.
>
> The unused field overhead would be smaller than currently page_ext, but
> getting rid of it when alloc profiling is not enabled would be more work
> than introducing an early boot param for the page_ext case. Could be however
> solved similarly to how page_ext is populated dynamically at runtime.
> Hopefully it wouldn't add noticeable cpu overhead.

Yes, slabobj_ext overhead is much smaller than page_ext one but still
considerable and it would be harder to eliminate. Boot-time resizing
of the extension object might be doable but that again would be quite
complex and better be done as a separate patchset. This is lower on my
TODO list than page_ext ones since the overhead is order of magnitude
smaller.

>
> >  static inline void __inc_lruvec_kmem_state(void *p, enum node_stat_item idx)
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 7bbdb0ddb011..9ecfcdb54417 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -979,6 +979,7 @@ config MEM_ALLOC_PROFILING
> >       depends on !DEBUG_FORCE_WEAK_PER_CPU
> >       select CODE_TAGGING
> >       select PAGE_EXTENSION
> > +     select SLAB_OBJ_EXT
> >       help
> >         Track allocation source code and record total allocation size
> >         initiated at that code location. The mechanism can be used to track
> > diff --git a/mm/slab.h b/mm/slab.h
> > index 77cf7474fe46..224a4b2305fb 100644
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -569,6 +569,10 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
> >
> >  static inline bool need_slab_obj_ext(void)
> >  {
> > +#ifdef CONFIG_MEM_ALLOC_PROFILING
> > +     if (mem_alloc_profiling_enabled())
> > +             return true;
> > +#endif
> >       /*
> >        * CONFIG_MEMCG_KMEM creates vector of obj_cgroup objects conditionally
> >        * inside memcg_slab_post_alloc_hook. No other users for now.
>
diff mbox series

Patch

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index f3584e98b640..2b010316016c 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1653,7 +1653,12 @@  unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
  * if MEMCG_DATA_OBJEXTS is set.
  */
 struct slabobj_ext {
+#ifdef CONFIG_MEMCG_KMEM
 	struct obj_cgroup *objcg;
+#endif
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+	union codetag_ref ref;
+#endif
 } __aligned(8);
 
 static inline void __inc_lruvec_kmem_state(void *p, enum node_stat_item idx)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 7bbdb0ddb011..9ecfcdb54417 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -979,6 +979,7 @@  config MEM_ALLOC_PROFILING
 	depends on !DEBUG_FORCE_WEAK_PER_CPU
 	select CODE_TAGGING
 	select PAGE_EXTENSION
+	select SLAB_OBJ_EXT
 	help
 	  Track allocation source code and record total allocation size
 	  initiated at that code location. The mechanism can be used to track
diff --git a/mm/slab.h b/mm/slab.h
index 77cf7474fe46..224a4b2305fb 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -569,6 +569,10 @@  int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 
 static inline bool need_slab_obj_ext(void)
 {
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+	if (mem_alloc_profiling_enabled())
+		return true;
+#endif
 	/*
 	 * CONFIG_MEMCG_KMEM creates vector of obj_cgroup objects conditionally
 	 * inside memcg_slab_post_alloc_hook. No other users for now.