| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> |
| Cc: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org>, Beena Emerson <memissemerson(at)gmail(dot)com> |
| Subject: | Re: increasing the default WAL segment size |
| Date: | 2017-01-09 18:40:30 |
| Message-ID: | CA+TgmobnhPN6Mprt8X-W61BKOM-_EVcHhQ+Ca0THdBxUGMyzTw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Jan 7, 2017 at 7:45 PM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:
> Well, now that there's 3 places that need to do almost the same thing, I
> think it'd be best to just centralize this somewhere. I realize that's not
> going to save any significant amount of code, but it would make it crystal
> clear what's going on (assuming the excellent comment above RIGHTMOST_ONE
> was kept).
Hmm. This sounds a lot like what fls() and my_log2() also do. I've
been quietly advocating for fls() because we only provide an
implementation in src/port if the operating system doesn't have it,
and the operating system may have an implementation that optimizes to
a single machine-language instruction (bsrl on x86, I think, see
4f658dc851a73fc309a61be2503c29ed78a1592e). But the fact that our
src/port implementation uses a loop instead of the RIGHTMOST_ONE()
trick seems non-optimal.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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