[Tarantool-patches] [PATCH v3 2/2] base64: improve decoder performance

[Sergey Nikiforov]

Hi!

On 24.12.2020 17:08, Leonid Vasiliev wrote:
> Hi! Thank you for the patch.
> AFAIU the status of the patch is follows:
> 
>  > But I see we are not going anywhere here. You don't really need LGTM
>  > from me on this patch, if you don't want to finish it. I am not
>  > strictly against these changes, because *probably* they don't add new
>  > bugs, and seem to be a tiny bit better for perf. I only don't like it
>  > being not finished.
> 
> I think the changes are ok, because they are good for perf (and we have
> confirmation) and don't add degradation (our tests should guarantee
> this).
> 
> See some comments below:
> 
> What about a benchmark. AFAIK A. Lyapunov propose saving all benchmarks
> that we used. Did you have a conversation with him?

Yes, I had. "perf" in tarantool. Benchmark framework is not yet merged 
(https://github.com/tarantool/tarantool/tree/i.kosarev/gh-5385-tiny-tuples-with-perf-test/perf) 
so I plan to commit my microbenchmark a little later to avoid duplication.

> On 22.12.2020 13:41, Sergey Nikiforov wrote:
>> Unnecessary checks were removed from internal loops.
>> Benchmark shows that performance is now ~1.19 times higher
>> (release build, Intel Core I7-9700K, only one thread).
>> ---
>>
>> Branch: 
>> https://github.com/tarantool/tarantool/tree/void234/gh-3069-fix-base64-memory-overrun-v3 
>>
>>
>>   test/unit/base64.c      |  7 +++-
>>   test/unit/base64.result | 84 +++++++++++++++++++++++++++--------------
>>   third_party/base64.c    | 36 +++++++++++++-----
>>   3 files changed, 89 insertions(+), 38 deletions(-)
>>
> 
> I left my questions about the test in the review of the previous patch.

Fixed.

>> diff --git a/third_party/base64.c b/third_party/base64.c
>> index 3350a98ff..93442c04b 100644
>> --- a/third_party/base64.c
>> +++ b/third_party/base64.c
>> @@ -257,10 +257,11 @@ base64_decode_block(const char *in_base64, int 
>> in_len,
>>           {
>>       case step_a:
>>               do {
>> -                if (in_pos == in_end || out_pos >= out_end)
>> +                if (in_pos >= in_end)
>>                   {
>>                       state->step = step_a;
>> -                    state->result = curr_byte;
>> +                    /* curr_byte is useless now */
>> +                    /* state->result = curr_byte; */
> 
> For multi-line comment, we use the following format:
> /*
>   * First line
>   * Second line
>   */
> 
> And leaving a commented code is not best practice.

Fixed.