[Crash-utility] [PATCH v6 0/7] Improve kernel modules symbol searching performance

[lijiang]

On Sat, Oct 16, 2021 at 1:21 PM Tao Liu <ltao at redhat.com> wrote:
>
> Currently the sequence for symbol_search to search a symbol is: 1) kernel
> symname hash table, 2) iterate all kernel symbols, 3) iterate all kernel
> modules and their symbols. In the worst case, if a non-exist symbol been
> searched, all 3 stages will be went through. The time consuming status for
> each stage is like:
>
>     stage 1         stage 2         stage 3
>     0.007000(ms)    0.593000(ms)    2.421000(ms)
>
> stage 3 takes too much time when comparing to stage 1. This patch introduces
> a symname hash table for kernel modules, to improve the performance of symbol
> searching.
>
> Functions symbol_search and symbol_exists are fundamental and widely used by
> other crash functions, thus the benefit of performance improvement can
> get accumulated. For example, "ps -m" and "irq" commands, which call
> the functions many times, will become faster with the patch.
>
> v5 -> v6:
>
> 1) Add mod_symname_hash table dump to help -s
> 2) Modified mod_symname_hash install/remove based on Kazu's suggestion.
>
> Tao Liu (7):
>   Implement install and remove operations for mod_symname_hash
>   Integrate symbol_search with mod_symname_hash search
>   Extend symname_hash_search with hash table select
>   Intergrate symbol_exists with mod_symname_hash search
>   Sync module symbols into mod_symtable whenever module symbols change
>   Refactor SYMNAME_HASH_INDEX macro to be a function
>   Add mod_symname_hash table dump to help -s
>
>  defs.h    |   3 +-
>  kernel.c  |   1 +
>  symbols.c | 261 +++++++++++++++++++++++++++++++++---------------------
>  3 files changed, 164 insertions(+), 101 deletions(-)
>

For the V6:  Acked-by: Lianbo Jiang <lijiang at redhat.com>
Thanks.
> --
> 2.29.2
>