| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Stephen Frost <sfrost(at)snowman(dot)net>,Sait Talha Nisanci <Sait(dot)Nisanci(at)microsoft(dot)com> |
| Cc: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com>,Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>,Dmitry Dolgov <9erthalion6(at)gmail(dot)com>,David Steele <david(at)pgmasters(dot)net>,Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>,pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [EXTERNAL] Re: WIP: WAL prefetch (another approach) |
| Date: | 2020-08-27 18:40:28 |
| Message-ID: | 6B918AFB-88D6-4687-8B4A-34C472E48BF4@anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On August 27, 2020 11:26:42 AM PDT, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
>Is WAL FPW compression enabled..? I'm trying to figure out how, given
>what's been shared here, that replaying 25GB of WAL is being helped out
>by 2.5x thanks to prefetch in the SSD case. That prefetch is hurting
>in
>the HDD case entirely makes sense to me- we're spending time reading
>pages from the HDD, which is entirely pointless work given that we're
>just going to write over those pages entirely with FPWs.
Hm? At least earlier versions didn't do prefetching for records with an fpw, and only for subsequent records affecting the same or if not in s_b anymore.
Andres
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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