[PATCH v2 0/4] alloc_tag: Introduce selective tracing for MAP

[Abhishek Bapat <abhishekbapat@google.com>]

The existing memory allocation profiling (MAP) tool accurately maintains
aggregate counters for overall memory accounting. However, relying
purely on aggregated counters restrics the visibility needed for
targeted debugging.

This patch series integrates three new tracepoints (alloc_tag_hit,
alloc_tag_mem_alloced and alloc_tag_mem_freed) directly into the
alloc_hooks_tag fast path.

Enabling trace events globally for all allocations introduces a severe
baseline overhead. To limit the performance overhead, we let the admin
select specific allocations to be traced.

A new IOCTL is introduced to allow privileged users to determine which
allocation tags need tracing enabled. The IOCTL utilizes the
pre-existing filtering mechanism to specify the allocation tags to
enable tracing on.

v2 changes:
- Patch 1/4: Changed the trace events for the page allocator to track
  pointer to the head page instead of codetag_ref.
  alloc_tag_trace_enabled() no longer takes a tag arg, that arg gets
  added in patch 2 instead where the function makes use of it.
  Introduced new sections in the Documentation expanding on the newly
  introduced trace events. Minor typo fixes.
- Patch 2/4: Toggle traces IOCTL now uses the same filter as other
  related ioctls. IOCTL returns -ENOENT if no tags match and an empty
  filter matches all tags. Added a subsection in the Documentation
  expanding on the new IOCTL.
- Patch 4/4: Updated the test to work with the new UAPI from patch 2.
  Updated commit message to accurately mention that the test flips the
  state of trace_on, verifies it and restores to the original state.

Abhishek Bapat (4):
  alloc_tag: Add trace events for tracing allocations
  alloc_tag: Introduce IOCTLs to toggle allocation tracepoints
  alloc_tag: Extend allocinfo_filter to support tracing queries
  alloc_tag: Add a test for trace state toggle and filtering

 Documentation/mm/allocation-profiling.rst     |  73 ++++++++
 MAINTAINERS                                   |   1 +
 include/linux/alloc_tag.h                     | 104 +++++++++---
 include/linux/codetag.h                       |   5 +-
 include/trace/events/alloc_tag.h              | 122 +++++++++++++
 include/uapi/linux/alloc_tag.h                |  21 ++-
 mm/alloc_tag.c                                | 160 +++++++++++++++++-
 mm/page_alloc.c                               |   4 +-
 mm/percpu.c                                   |  12 +-
 mm/slub.c                                     |   6 +-
 .../alloc_tag/allocinfo_ioctl_test.c          | 113 ++++++++++++-
 11 files changed, 573 insertions(+), 48 deletions(-)
 create mode 100644 include/trace/events/alloc_tag.h


base-commit: a663a4c75b63341fa6cc16e15feb29f36321f5f2
-- 
2.56.0.385.gd3acb90ef8-goog