[PATCH v4 0/8] kallsyms: Optimizes the performance of lookup symbols

Zhen Lei
2022-09-20T07:14:22Z

v3 --> v4:
1. Move the declaration of function kallsyms_sym_address() to linux/kallsyms.h,
fix a build warning.

v2 --> v3:
1. Improve test cases, perform complete functional tests on functions
kallsyms_lookup_name(), kallsyms_on_each_symbol() and
kallsyms_on_each_match_symbol().
2. Add patch [PATCH v3 2/8] scripts/kallsyms: ensure that all possible
combinations are compressed.
3. The symbol type is not compressed regardless of whether
CONFIG_KALLSYMS_ALL is set or not. The memory overhead is increased
by less than 20KiB if CONFIG_KALLSYMS_ALL=n.
4. Discard [PATCH v2 3/8] kallsyms: Adjust the types of some local variables

v1 --> v2:
Add self-test facility

v1:
Currently, to search for a symbol, we need to expand the symbols in
'kallsyms_names' one by one, and then use the expanded string for
comparison. This is very slow.

In fact, we can first compress the name being looked up and then use
it for comparison when traversing 'kallsyms_names'.

This patch series optimizes the performance of function kallsyms_lookup_name(),
and function klp_find_object_symbol() in the livepatch module. Based on the
test results, the performance overhead is reduced to 5%. That is, the
performance of these functions is improved by 20 times.

To avoid increasing the kernel size in non-debug mode, the optimization is only
for the case CONFIG_KALLSYMS_ALL=y.

Zhen Lei (8):
scripts/kallsyms: rename build_initial_tok_table()
scripts/kallsyms: ensure that all possible combinations are compressed
scripts/kallsyms: don't compress symbol types
kallsyms: Improve the performance of kallsyms_lookup_name()
kallsyms: Add helper kallsyms_on_each_match_symbol()
livepatch: Use kallsyms_on_each_match_symbol() to improve performance
livepatch: Improve the search performance of
module_kallsyms_on_each_symbol()
kallsyms: Add self-test facility

include/linux/kallsyms.h | 9 +
init/Kconfig | 13 ++
kernel/Makefile | 1 +
kernel/kallsyms.c | 106 +++++++++-
kernel/kallsyms_selftest.c | 423 +++++++++++++++++++++++++++++++++++++
kernel/livepatch/core.c | 25 ++-
kernel/module/kallsyms.c | 13 +-
scripts/kallsyms.c | 24 ++-
8 files changed, 598 insertions(+), 16 deletions(-)
create mode 100644 kernel/kallsyms_selftest.c

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2.25.1