| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, YUriy Zhuravlev <u(dot)zhuravlev(at)postgrespro(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Move PinBuffer and UnpinBuffer to atomics |
| Date: | 2016-03-28 15:38:43 |
| Message-ID: | 20160328153843.GA750908@alvherre.pgsql |
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| Lists: | pgsql-hackers |
Andres Freund wrote:
> On 2016-03-28 15:46:43 +0300, Alexander Korotkov wrote:
> > @@ -932,8 +936,13 @@ ReadBuffer_common(SMgrRelation smgr, cha
> >
> > if (isLocalBuf)
> > {
> > - /* Only need to adjust flags */
> > - bufHdr->flags |= BM_VALID;
> > + /*
> > + * Only need to adjust flags. Since it's local buffer, there is no
> > + * concurrency. We assume read/write pair to be cheaper than atomic OR.
> > + */
> > + uint32 state = pg_atomic_read_u32(&bufHdr->state);
> > + state |= BM_VALID;
> > + pg_atomic_write_u32(&bufHdr->state, state);
>
> I'm not a fan of repeating that comment in multiple places. Hm.
Perhaps a set of macros should be offered that do "read, set some flag,
write". Then the comments can be attached to the macro instead of to
each callsite.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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