Re: PATCH: pgbench - merging transaction logs

>> I also implemented a quick and dirty version for a merge log based on
>> sharing a file handle (append mode + sprintf + fputs).

I tried the "append + per-thread 2KB buffered sprintf + fputs when full",
with the same number of runs. The logs are out of order by chunks, the 
overhead seems higher with 1 thread, but there is no extra overhead
with 12 threads.

>> The results are as follow:
>>
>>  * 1 thread 33 runs median tps (average is consistent):
>>  - no logging:        22062
>>  - separate logging:  19360  (-12.2%)
>>  - merged logging:    19326  (-12.4%, not significant from previous)
 - buf merged logging:   18751 (-15%, seems significant)

>> The worst overhead I could trigger is with 12 threads:
>>
>>  * 12 threads 35 runs median tps (average is consistent)
>>  - no logging:       155917
>>  - separate logging: 124695 (-20.0%)
>>  - merged logging:   119349 (-23.5%)
 - buf merged logging: 124914 (-19.9%, not significant from separate)

-- 
Fabien.