Re: [PATCH] backend: compare word-at-a-time in bcTruelen

Heikki Linnakangas wrote:
> Jeremy Kerr wrote:
>>> Speaking of which, what about some performance numbers?
>>
>> OK, benchmarks done:
>>
>>  http://ozlabs.org/~jk/projects/db/data/postgres.bcTruelen/
>>
>> Summary: small increase in performance (~1-2% on my machine), at about 
>> 1.5 standard deviations from the mean. Profiles show a decent drop in 
>> hits within .
>>
>> However: Sysbench seems to be quite heavy with the fixed-width char 
>> types, so may end up calling bcTruelen more than most workloads. Would 
>> be nice to get some x86 numbers too, but I don't have a suitable 
>> machine here.
>>
>> So: The increase in performance is positive on this workload, albeit 
>> fairly minor. Downside is increased code complexity.
> 
> Based on this benchmark, I don't think this patch is worth it..

what exactly is getting graphed here - is the what sysbench reports as 
transactions/s or the operations/queries per second? if yes it is 
important to notice that sysnbench by default executes multiple queries 
per transaction and and several different kind of queries. Only some of 
those queries have bcTruelen() showing up on top of the profile.



Stefan