On 2022/9/16 9:27, Leizhen (ThunderTown) wrote:

Hi, everybody:
  Can anyone review it? Maybe I should split this patch series
into two parts: kallsyms and livepatch.
  In fact, the performance can be improved even if the compression policy
of the symbol type is not changed, that is, the scripts/callsyms.c file is
not modified, but we perform the len-based filtering first. That way, it'll
be easier for everyone to review. OK, I'm ready for v3.

Sorry, I didn't sleep well yesterday. The length is the length of the
compressed string. Therefore, the solution is not feasible.

On 2022/9/9 21:00, Zhen Lei wrote:

quoted

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: don't compress symbol type when
    CONFIG_KALLSYMS_ALL=y
  scripts/kallsyms: rename build_initial_tok_table()
  kallsyms: Adjust the types of some local variables
  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   |   8 ++
 init/Kconfig               |  13 ++
 kernel/Makefile            |   1 +
 kernel/kallsyms.c          | 135 ++++++++++++++++++++-
 kernel/kallsyms_selftest.c | 243 +++++++++++++++++++++++++++++++++++++
 kernel/livepatch/core.c    |  25 +++-
 kernel/module/kallsyms.c   |  13 +-
 scripts/kallsyms.c         |  19 ++-
 8 files changed, 441 insertions(+), 16 deletions(-)
 create mode 100644 kernel/kallsyms_selftest.c

-- 
Regards,
  Zhen Lei