Re: Faster inserts with mostly-monotonically increasing values

On Mon, Mar 19, 2018 at 11:57 AM, Pavan Deolasee
<pavan(dot)deolasee(at)gmail(dot)com> wrote:
>
>
> On Thu, Mar 15, 2018 at 7:51 AM, Claudio Freire <klaussfreire(at)gmail(dot)com>
> wrote:
>>
>>
>>
>> I applied the attached patches on top of your patch, so it would be
>> nice to see if you can give it a try in your test hardware to see
>> whether it helps.
>
>
> I can confirm that I no longer see any regression at 8 or even 16 clients.
> In fact, the patched version consistent do better than master even at higher
> number of clients.
>
> The only thing I am a bit puzzled is that I am no longer able to reproduce
> the 40-50% gains that I'd earlier observed with a single client. I now get
> 20-25% with smaller number of client and 10-15% with larger number of
> clients. I haven't been able to establish why it's happening, but since it's
> a different AWS instance (though of the same type), I am inclined to blame
> it on that for now.

Your original patch also skipped the check for serializable conflicts.

*IF* that was correct, it probably further reduced contention. I'm not
entirely sure if skipping that check is correct, but if it is, you can
still accomplish this checking whether the new key is beyond the
current rightmost key, and setting a flag so that check is later
skipped.

But there are lots of complex interactions in that code and I'm no
expert there, I'd prefer if someone more knowledgeable could confirm
whether it's safe to skip that check or not. Or leave it just in case.