Re: [PATCH v2 1/6] gdb/record: Refactor record history

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

Hello Guinevere,

Thanks! It all looks good to me now.

Guinevere Larsen <guinevere@redhat.com> writes:

> This is the first step in a large refactor in how GDB keeps execution
> history.  Rather than using a linked list where multiple entries can
> describe a single instruction, the history will now be stored in an
> std::deque, each instruction being one entry in the deque.
>
> The choice was initially to use an std::vector, but it would become
> unwieldy because it needs all the memory to be consecutive, which is
> hard for 200 thousand entries. Deque was picked because it was a nice
> midpoint between vector (maximum cache cohesion) and linked list
> (maximum ease of finding space to store more).
>
> Each instruction in memory will be now one record_full_instruction
> entry, which for this commit just contains a vector of
> record_full_entry for the effects of the instruction, and the data that
> was stored in the record_full_end entry (that is, the instruction number
> and the signal, if any).
>
> This change introduced a minimal performance improvement (what's
> important is that it isn't a degradation) and a  reduction in the total
> memory footprint of roughly 20% if the entire history is used.
> ---
>  gdb/aarch64-tdep.c     |    2 -
>  gdb/amd64-linux-tdep.c |    3 -
>  gdb/arm-tdep.c         |    2 -
>  gdb/i386-linux-tdep.c  |    3 -
>  gdb/i386-tdep.c        |    4 -
>  gdb/loongarch-tdep.c   |    2 -
>  gdb/moxie-tdep.c       |    2 -
>  gdb/ppc-linux-tdep.c   |    3 -
>  gdb/record-full.c      | 1180 ++++++++++++++++------------------------
>  gdb/record-full.h      |    1 -
>  gdb/riscv-tdep.c       |    3 -
>  gdb/rs6000-tdep.c      |    4 -
>  gdb/s390-linux-tdep.c  |    3 -
>  gdb/s390-tdep.c        |    2 -
>  14 files changed, 476 insertions(+), 738 deletions(-)

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>

-- 
Thiago