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Re: [RFC] Deprecate Berkelety DB filesystem backend

From: Mark Phippard <markphip_at_gmail.com>
Date: Mon, 7 Jan 2013 11:10:00 -0500

On Mon, Jan 7, 2013 at 5:40 AM, Philip Martin
<philip.martin_at_wandisco.com> wrote:
> Branko ─îibej <brane_at_wandisco.com> writes:
>
>> 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.
>
> Given the Linux numbers the problem is OSX specific and not inherent to
> BDB. Repository access in the testsuite is all single-thread and
> single-process so any BDB locking should be trivial. If we don't drop
> BDB then we shoud attempt to find out why BDB is slow on OSX.

I also think this is specific to OSX. I reported this problem several
years ago on the list:

http://svn.haxx.se/dev/archive-2008-04/0602.shtml

As you can see from my email, the problem I was seeing seemed to be
just in creating the repository. There was a significant time penalty
and multiplied across the number of times the tests create
repositories it really added up. I never figured out why this takes
so long on OSX. I recall it was pretty easy to look at the tests.log
and see where these unnatural delays existed. I recall it was mostly
in setting up each new test, not the test itself.

-- 
Thanks
Mark Phippard
http://markphip.blogspot.com/
Received on 2013-01-07 17:10:32 CET

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