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Re: GiST index performance

From: Matthew Wakeling <matthew(at)flymine(dot)org>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: GiST index performance
Date: 2009-06-11 16:42:11
Message-ID: alpine.DEB.2.00.0906111737490.4337@aragorn.flymine.org (view raw or flat)
Thread:
Lists: pgsql-performance
On Thu, 11 Jun 2009, Tom Lane wrote:
> So it'd be worth converting your functions to V1 style.

Does that produce a significant reduction in overhead? (You'll probably 
say "yes, that's the whole point").

> hmm ... memcpy or qsort maybe?

Surprise:

CPU: Core 2, speed 1998 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        image name               app name                 symbol name
3005354  40.2868  libc-2.9.so              libc-2.9.so              __mcount_internal
1195592  16.0269  libc-2.9.so              libc-2.9.so              mcount
549998    7.3727  postgres                 postgres                 gistnext
420465    5.6363  postgres                 postgres                 fmgr_oldstyle
376333    5.0447  no-vmlinux               no-vmlinux               (no symbols)
210984    2.8282  postgres                 postgres                 FunctionCall5
182509    2.4465  postgres                 postgres                 gistdentryinit
174356    2.3372  btree_gist.so            btree_gist.so            gbt_int4_consistent
142829    1.9146  postgres                 postgres                 FunctionCall1
129800    1.7400  postgres                 postgres                 .plt
119180    1.5976  nvidia_drv.so            nvidia_drv.so            (no symbols)
96351     1.2916  libxul.so                libxul.so                (no symbols)
91726     1.2296  btree_gist.so            btree_gist.so            gbt_num_consistent

A quick grep in the postgres source for mcount reveals no hits. No idea 
what it does - there is no man page for it.

Matthew

-- 
 I pause for breath to allow you to get over your shock that I really did cover
 all that in only five minutes...        -- Computer Science Lecturer

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Subject: Re: GiST index performance
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Subject: Re: Postgres replication: dump/restore, PITR, Slony,...?

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