| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Ants Aasma <ants(at)cybertec(dot)at> |
| Subject: | Re: better atomics - v0.6 |
| Date: | 2014-09-24 16:44:09 |
| Message-ID: | 18919.1411577049@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On 2014-09-24 18:55:51 +0300, Heikki Linnakangas wrote:
>> There doesn't seem to be any hardware implementations of that in the patch.
>> Is there any architecture that has an instruction or compiler intrinsic for
>> that?
> You can implement it rather efficiently on ll/sc architectures. But I
> don't really think it matters. I prefer add_until (I've seen it named
> saturated add before as well) to live in the atomics code, rather than
> reimplement it in atomics employing code. I guess you see that
> differently?
I think the question is more like "what in the world happened to confining
ourselves to a small set of atomics". I doubt either that this exists
natively anywhere, or that it's so useful that we should expect platforms
to have efficient implementations.
regards, tom lane
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