linux-kernel - [PATCH 0/7] kallsyms: Optimizes the performance of lookup symbols

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Date:   Thu, 8 Sep 2022 21:09:29 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        <live-patching@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Luis Chamberlain" <mcgrof@...nel.org>,
        <linux-modules@...r.kernel.org>
CC:     Zhen Lei <thunder.leizhen@...wei.com>
Subject: [PATCH 0/7] kallsyms: Optimizes the performance of lookup symbols

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 (7):
  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()

 include/linux/kallsyms.h |   8 +++
 kernel/kallsyms.c        | 135 +++++++++++++++++++++++++++++++++++++--
 kernel/livepatch/core.c  |  25 ++++++--
 kernel/module/kallsyms.c |  13 +++-
 scripts/kallsyms.c       |  19 ++++--
 5 files changed, 184 insertions(+), 16 deletions(-)

-- 
2.25.1