This patchset implements several improvements: 1. Gracefully handles module unloading while there are used allocations allocated from that module; 2. Provides an option to reduce memory overhead from storing page allocation references by indexing allocation tags; 3. Provides an option to store page allocation tag references in the page flags, removing dependency on page extensions and eliminating the memory overhead from storing page allocation references (~0.2% of total system memory). 4. Improves page allocation performance when CONFIG_MEM_ALLOC_PROFILING is enabled by eliminating page extension lookup. Page allocation performance overhead is reduced from 14% to 5.5%. Patch #1 introduces mas_for_each_rev() helper function. Patch #2 copies module tags into virtually contiguous memory which serves two purposes: - Lets us deal with the situation when module is unloaded while there are still live allocations from that module. Since we are using a copy version of the tags we can safely unload the module. Space and gaps in this contiguous memory are managed using a maple tree. - Enables simple indexing of the tags in the later patches. Preallocated virtually contiguous memory size can be configured using max_module_alloc_tags kernel parameter. Patch #3 is a code cleanup to simplify later changes. Patch #4 abstracts page allocation tag reference to simplify later changes. Patch #5 lets us control page allocation tag reference sizes and introduces tag indexing. Patch #6 adds a config to store page allocation tag references inside page flags if they fit. Patchset applies to mm-unstable. Changes since v1 [1]: - introduced mas_for_each_rev() and use it, per Liam Howlett - use advanced maple_tree API to minimize lookups, per Liam Howlett - fixed CONFIG_MODULES=n configuration build, per kernel test robot [1] https://lore.kernel.org/all/20240819151512.2363698-1-surenb@xxxxxxxxxx/ Suren Baghdasaryan (6): maple_tree: add mas_for_each_rev() helper alloc_tag: load module tags into separate continuous memory alloc_tag: eliminate alloc_tag_ref_set alloc_tag: introduce pgalloc_tag_ref to abstract page tag references alloc_tag: make page allocation tag reference size configurable alloc_tag: config to store page allocation tag refs in page flags .../admin-guide/kernel-parameters.txt | 4 + include/asm-generic/codetag.lds.h | 19 ++ include/linux/alloc_tag.h | 46 ++- include/linux/codetag.h | 40 ++- include/linux/maple_tree.h | 14 + include/linux/mmzone.h | 3 + include/linux/page-flags-layout.h | 10 +- include/linux/pgalloc_tag.h | 287 +++++++++++++--- kernel/module/main.c | 67 ++-- lib/Kconfig.debug | 36 +- lib/alloc_tag.c | 321 ++++++++++++++++-- lib/codetag.c | 104 +++++- mm/mm_init.c | 1 + mm/page_ext.c | 2 +- scripts/module.lds.S | 5 +- 15 files changed, 826 insertions(+), 133 deletions(-) base-commit: 18d35b7e30d5a217ff1cc976bb819e1aa2873301 -- 2.46.0.469.g59c65b2a67-goog
