Re: Should we cacheline align PGXACT?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Should we cacheline align PGXACT?
Date: 2016-08-20 18:38:52
Message-ID: 29160.1471718332@sss.pgh.pa.us
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> Wow, nice results. My intuition on why PGXACT helped in the first place was that it minimized the number of cache lines that had to be touched to take a snapshot. Padding obviously would somewhat increase that again, so I can't quite understand why it seems to be helping... any idea?

That's an interesting point. I wonder whether this whole thing will be
useless or even counterproductive after (if) Heikki's CSN-snapshot patch
gets in. I would certainly not mind reverting the PGXACT/PGPROC
separation if it proves no longer helpful after that.

regards, tom lane

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