Re: [RFC] Deprecate Berkelety DB filesystem backend

On 05.01.2013 11:35, Philip Martin wrote:
> Branko Čibej <brane_at_wandisco.com> writes:
>
>> * The BDB backend is an order of magnitude slower on trunk than FSFS
>> o timing parallel "make check" on my 4x4-core i7+ssd mac:
>> + FSFS: real 7m33.213s, user 19m8.075s, sys 10m54.739s
>> + BDB: real 35m17.766s, user 15m28.395s, sys 11m58.824s
> I don't see that behaviour. On my machine with 1x2 Core2 Duo, Linux and
> SSD:
>
> FSFS: real 12m42.383s, user 7m37.557s, sys 5m58.534s
> BDB: real 11m30.895s, user 8m14.603s, sys 5m45.358s

Interesting that i's that much slower on the Mac. But considering my
numbers:

  * FSFS: real 7m33.213s, user 19m8.075s, sys 10m54.739s
  * BDB: real 35m17.766s, user 15m28.395s, sys 11m58.824s

Notice that the sys and user times are comparable, yet real-time is an
order of magnitude higher with BDB. Also, in the FSFS case, real time is
actually lower than user or sys time, which makes sense for parallel
tests. I interpret that as meaning that FSFS parallelizes (across
different processes) better than BDB, and that BDB spends most of its
time twiddling its thumbs waiting for I/O.

> I don't think either your results or mine indicate anything about the
> relative performance of the backends as all the repositories in the
> testsuite are far too small.

That's true. Of course, the numbers are only one data point, personally
I think the long-term maintenance costs are much more important.

One thing I /don't/ know is what percentage of the Subversion installed
base (in both number of repositories and repository size) falls to BDB.
Does anyone have any idea about that?

-- Brane

-- 
Branko Čibej
Director of Subversion | WANdisco | www.wandisco.com