what if native systemd service is slower than old sysvinit script?

[Michał Piotrowski]

2011/9/14 Jef Spaleta <jspaleta at gmail.com>:
>
>
> 2011/9/14 Michał Piotrowski <mkkp4x4 at gmail.com>
>>
>> Exactly. F15, PostgreSQL 9.0 and just service file from PostgreSQL
>> 9.1. Root filesystem and database are on SSD and Ext4.
>>
>
> Okay... brace yourself.
>
> I just ran this test on my non-SSD ext4 based F15 system and I get the
> opposite result on start...repeatably.  On my system the systemd based start
> up in the admittedly simple service postgresql start  testing is
> consistently faster by about a second.   And just as interesting... my
> sysinit times are slower than yours, that's a real head scratcher for me.
> If my db test was less overall work to init for some reason I'd expect my
> numbers to be faster than yourse in both cases. I have no off the top of my
> head theory that could explain that except that your low level disk i/o is
> significantly different than mine.
>
> Both variants of "service postgresql stop" is within a 1/10 of a second in
> my testing
>
> I can give you the  screen log captures for my tests if you desire to review
> my actions but here here is the summary for my simple timing test:  And
> admittedly I'm using a simply initiated postgres db. It could be that your
> real world database initialization workload is more intensive than my test
> and the disk i/o is now a limiting factor in a different way.
>
> And of course my numbers do not discount what your seeing as my test is as
> anecdotal as your is. Your numbers may still be indicative of a more nuanced
> problem that can be resolved and its good to have your numbers as a starting
> point for a discussion around understanding optimization issues (like disk
> i/o). We just can't jump to conclusions about why you are seeing what your
> are seeing. I hope my numbers serve as a cautionary reminder to those others
> on this list that benchmarking disk io intensive tasks can be very complex
> and very system dependent.  Certain other people in this discussion are
> being overly bombastic and seem to have forgotten this fact.  I hope for all
> our sakes they can find a way to ratchet down the hyperbole and look at
> these sort of issues with a more clinical approach.
>
>
>
> Okay so here's my summary of the quick tests.  Please if you have an updated
> methodology for me to test, let me know. I'm willing to reuse a specially
> crafted pgsql database if you feel that will help you. Though I'd think we
> wan't to do that sort of deep dive comparison off list until we are ready to
> publish some summaries after we both feel comfortable with the test runs.

It seems to me that the database settings or database content has
nothing to do with my test results. Yesterday I removed all databases
(it's only development system) and I did the whole setup again.
Results are the same. So I came to the conclusion that it must be
relevant to some other factor. Thanks for sending your test results.
Later I'll try to work out this problem.

>
> -jef
>
> ==========================================
> SysVinit:
> service postgresql status
> postgresql.service - LSB: start and stop PostgreSQL server
>           Loaded: loaded (/etc/rc.d/init.d/postgresql)
>           Active: inactive (dead)
>           CGroup: name=systemd:/system/postgresql.service
>
>
> time service postgresql start
> real    0m2.329s
> user    0m0.028s
> sys     0m0.046s
>
>
> time service postgresql stop
> real    0m1.281s
> user    0m0.035s
> sys     0m0.096s
>
> time service postgresql start
> real    0m2.242s
> user    0m0.031s
> sys     0m0.038s
>
> time service postgresql stop
> real    0m1.235s
> user    0m0.031s
> sys     0m0.036s
>
>
> =========================================
> Systemd based:
> status postgresql.service
> postgresql.service - PostgreSQL database server
>           Loaded: loaded (/lib/systemd/system/postgresql.service)
>           Active: inactive (dead)
>           CGroup: name=systemd:/system/postgresql.service
>
>
> time service postgresql start
> real    0m1.141s
> user    0m0.019s
> sys     0m0.019s
>
>
> time service postgresql stop
> real    0m1.146s
> user    0m0.017s
> sys     0m0.017s
>
> time service postgresql start
> real    0m1.153s
> user    0m0.016s
> sys     0m0.019s
>
> time service postgresql stop
> real    0m1.144s
> user    0m0.026s
> sys     0m0.014s
>
>
>
>
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-- 
Best regards,
Michal

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