Re: better atomics - Mailing list pgsql-hackers

From Tom Lane
Subject Re: better atomics
Date
Msg-id 10161.1382990807@sss.pgh.pa.us
Whole thread Raw
In response to Re: better atomics  (Heikki Linnakangas <hlinnakangas@vmware.com>)
Responses Re: better atomics  (Andres Freund <andres@2ndquadrant.com>)
List pgsql-hackers
Heikki Linnakangas <hlinnakangas@vmware.com> writes:
> On 28.10.2013 21:32, Andres Freund wrote:
>> I think there are quite some algorithms relying on 16byte CAS, that's
>> why I was thinking about it at all. I think it's easier to add support
>> for it in the easier trawl through the compilers, but I won't argue much
>> for it otherwise for now.

> Many algorithms require a 2*(pointer width) CAS instruction. On 64-bit 
> platforms that's 16 bytes, but on 32-bit platforms an 8 byte version 
> will suffice.

You're both just handwaving.  How many is "many", and which ones might
we actually have enough use for to justify dealing with such a dependency?
I don't think we should buy into this without some pretty concrete
justification.
        regards, tom lane



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