Re: shared memory release following failed lock acquirement. - Mailing list pgsql-hackers

From Merlin Moncure
Subject Re: shared memory release following failed lock acquirement.
Date
Msg-id 6EE64EF3AB31D5448D0007DD34EEB3412A74D8@Herge.rcsinc.local
Whole thread Raw
In response to shared memory release following failed lock acquirement.  ("Merlin Moncure" <merlin.moncure@rcsonline.com>)
Responses Re: shared memory release following failed lock acquirement.  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
Tgl wrote:
> > As I see it, this means the user-locks (and perhaps all
> > locks...?) eat around ~ 6k bytes memory each.
>
> They're allocated in groups of 32, which would work out to close to
6k;
> maybe you were measuring the incremental cost of allocating the first
one?

I got my 6k figure by dividing 10000 into 64M, 10000 being the value
that crashed the server.  That's reasonable because doubling shared
buffers slightly more than doubled the crash value.

I was wondering how ~ 10k locks ran me out of shared memory when each
lock takes ~ 260b (half that, as you say) and I am running 8k buffers =
64M.

260 * 100 backends * 64 maxlocks = 1.7 M.  Sure, the hash table and
other stuff adds some...but this is no where near what it should take to
run me out.

Am I just totally misunderstanding how to estimate locks memory
consumption?

Merlin


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