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

[Tao Liu]

Hi Lijiang,

On Sat, Oct 23, 2021 at 9:27 AM lijiang <lijiang at redhat.com> wrote:
>
> 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.

Thanks for reviewing the patch set and ack!

Thanks,
Tao Liu

> > --
> > 2.29.2
> >
>