[lld] r319518 - Add an additional test for r319503.

[Rafael Avila de Espindola via llvm-commits]

Rui Ueyama <ruiu at google.com> writes:

> On Mon, Dec 4, 2017 at 5:30 PM, Rafael Avila de Espindola <
> rafael.espindola at gmail.com> wrote:
>
>> Rui Ueyama <ruiu at google.com> writes:
>>
>> > On Sat, Dec 2, 2017 at 9:09 AM, Rafael Espíndola <
>> rafael.espindola at gmail.com
>> >> wrote:
>> >
>> >> > This time I just timed the llvm tests when built with shared libraries
>> >> >
>> >> > gold:                                  138.207661064 seconds time
>> elapsed
>> >> > lld master:                         143.343427881 seconds time elapsed
>> >> > cutting bloom filter in half: 148.267076771 seconds time elapsed
>> >> > bloom filter of size 1:         180.053104591 seconds time elapsed
>> >
>> >
>> > Did you know why gold is faster than us?
>>
>> Some of it is the number of buckets. Going from /4 to /2 in lld takes
>> the test time to 142.5 seconds.
>>
>
> Thanks. But that doesn't explain the difference that much though.
>
> I can't think of any other parameters we can tweak to optimize the
> .gnu.hash table, so the difference might come from differences in other
> parts of the DSOs.

The gold .gnu.hash is over 2x larger than ours. It also uses a prime
number. For libLLVMSupport for example the patched lld uses 960 buckets,
gold uses 1031.

The 2x experiment in lld just shows that their is potential for improving
our .gnu.hash.

Cheers,
Rafael