Re: [PATCH v3 21/35] mm/slab: add allocation accounting into slab allocation and free paths

On Fri, Feb 16, 2024 at 8:39 AM Kent Overstreet
[off-list ref] wrote:

On Fri, Feb 16, 2024 at 05:31:11PM +0100, Vlastimil Babka wrote:

quoted

On 2/12/24 22:39, Suren Baghdasaryan wrote:

quoted

Account slab allocations using codetag reference embedded into slabobj_ext.

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>
---
 mm/slab.h | 26 ++++++++++++++++++++++++++
 mm/slub.c |  5 +++++
 2 files changed, 31 insertions(+)

diff --git a/mm/slab.h b/mm/slab.h
index 224a4b2305fb..c4bd0d5348cb 100644
--- a/mm/slab.h
+++ b/mm/slab.h

@@ -629,6 +629,32 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)

 #endif /* CONFIG_SLAB_OBJ_EXT */

+#ifdef CONFIG_MEM_ALLOC_PROFILING
+
+static inline void alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab,
+                                   void **p, int objects)
+{
+   struct slabobj_ext *obj_exts;
+   int i;
+
+   obj_exts = slab_obj_exts(slab);
+   if (!obj_exts)
+           return;
+
+   for (i = 0; i < objects; i++) {
+           unsigned int off = obj_to_index(s, slab, p[i]);
+
+           alloc_tag_sub(&obj_exts[off].ref, s->size);
+   }
+}
+
+#else
+
+static inline void alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab,
+                                   void **p, int objects) {}
+
+#endif /* CONFIG_MEM_ALLOC_PROFILING */

You don't actually use the alloc_tagging_slab_free_hook() anywhere? I see
it's in the next patch, but logically should belong to this one.

I don't think it makes any sense to quibble about introducing something
in one patch that's not used until the next patch; often times, it's
just easier to review that way.

Yeah, there were several cases where I was debating with myself which
way to split a patch (same was, as you noticed, with
prepare_slab_obj_exts_hook()). Since we already moved
prepare_slab_obj_exts_hook(), alloc_tagging_slab_free_hook() will
probably move into the same patch. I'll go over the results once more
to see if the new split makes more sense, if not will keep it here.
Thanks!