| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Subject: | Re: Atomics for heap_parallelscan_nextpage() |
| Date: | 2017-08-16 17:44:28 |
| Message-ID: | 31090.1502905468@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> Don't think we require BUFFERALIGN - MAXALIGN ought to be
> sufficient.
Uh, see my other message just now.
> The use of BUFFERALIGN presumably is to space out things
> into different cachelines, but that doesn't really seem to be important
> with this. Then we can just avoid defining the new macro...
I was feeling a bit uncomfortable with the BUFFERALIGN_DOWN() for a
different reason: if the caller has specified the exact amount of space it
needs, having shm_toc_create discard some could lead to an unexpected
failure. I wonder whether maybe shm_toc_create should just error out if
the number it's handed isn't aligned already.
>> + return BUFFERALIGN(
>> + add_size(offsetof(shm_toc, toc_entry),
>> + add_size(mul_size(e->number_of_keys, sizeof(shm_toc_entry)),
>> + e->space_for_chunks)));
> I think splitting this into separate statements would be better.
+1, it was too complicated already.
regards, tom lane
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