Re: [PATCH v3 20/35] lib: add codetag reference into slabobj_ext
From: Vlastimil Babka <hidden>
Date: 2024-02-16 15:36:20
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cgroups, linux-arch, linux-doc, linux-fsdevel, linux-iommu, linux-mm, lkml
On 2/12/24 22:39, Suren Baghdasaryan wrote:
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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.
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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 trackdiff --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.