| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Antonin Houska <ah(at)cybertec(dot)at> |
| Cc: | Michael Paquier <michael(at)paquier(dot)xyz>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Attempt to consolidate reading of XLOG page |
| Date: | 2019-11-22 13:35:51 |
| Message-ID: | 20191122133551.GA4216@alvherre.pgsql |
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| Lists: | pgsql-hackers |
On 2019-Nov-22, Antonin Houska wrote:
> I thought that in [1] you try discourage me from using pg_pread(), but now it
> seems to be the opposite. Ideally I'd like to see no overhead added by my
> patch at all, but the code simplicity should matter too.
FWIW I think the new code is buggy because it doesn't seem to be setting
ws_off, so I suppose the optimization in ReadPageInternal to skip
reading the page when it's already the page we have is not hit, except
for the first page in the segment. I didn't verify this, just my
impression while reading the code.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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