| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, Noah Misch <noah(at)leadboat(dot)com>, Jason Petersen <jason(at)citusdata(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-bugs(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Concurrent ALTER SEQUENCE RESTART Regression |
| Date: | 2017-05-11 20:40:12 |
| Message-ID: | 20170511204012.pf2k4jmauyebfxkw@alap3.anarazel.de |
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| Lists: | pgsql-bugs pgsql-hackers |
Hi,
On 2017-05-11 16:27:48 -0400, Peter Eisentraut wrote:
> On 5/10/17 12:24, Andres Freund wrote:
> > Upthread I theorized whether
> > that's actually still meaningful given fastpath locking and such, but I
> > guess we'll have to evaluate that.
>
> I did some testing.
That's with the open_share_lock stuff ripped out entirely, replaced by a
plain lock acquisition within the current subxact?
> (These were within each other's variance over several runs.)
>
> 9.2 unpatched
> Time: 64868.305 ms
>
> 9.2 patched
> Time: 60585.317 ms
>
> (So without contention fast-path locking beats the extra dance that
> open_share_lock() does.)
That's kind of surprising, I really wouldn't have thought it'd be faster
without. I guess it's the overhead of sigsetjmp(). Cool.
- Andres
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