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

[Guinevere Larsen <guinevere@redhat.com>]

On 4/28/26 12:28 AM, Thiago Jung Bauermann wrote:
> 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>
>
Thanks for all the reviews! I applied your review tag to all the 
patches, but I will wait until next thursday, so that anyone has time to 
give thoughts before I self-approve the patch series.

-- 
Cheers,
Guinevere Larsen
It/she