| From: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Stephen Frost <sfrost(at)snowman(dot)net>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, Andres Freund <andres(at)anarazel(dot)de>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: WIP: WAL prefetch (another approach) |
| Date: | 2020-10-06 05:04:57 |
| Message-ID: | CA+hUKGJyuSTC5sXTv-2FmtjfFPYFU8t8JPnhV4jdMKmuKJ4tHw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Sep 24, 2020 at 11:38 AM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> On Wed, Sep 9, 2020 at 11:16 AM Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> > OK, thanks for looking into this. I guess I'll wait for an updated patch
> > before testing this further. The storage has limited capacity so I'd
> > have to either reduce the amount of data/WAL or juggle with the WAL
> > segments somehow. Doesn't seem worth it.
>
> Here's a new WIP version that works for archive-based recovery in my tests.
Rebased over recent merge conflicts in xlog.c. I also removed a stray
debugging message.
One problem the current patch has is that if you use something like
pg_standby, that is, a restore command that waits for more data, then
it'll block waiting for WAL when it's trying to prefetch, which means
that replay is delayed. I'm not sure what to think about that yet.
| Attachment | Content-Type | Size |
|---|---|---|
| v12-0001-Add-pg_atomic_unlocked_add_fetch_XXX.patch | text/x-patch | 3.4 KB |
| v12-0002-Improve-information-about-received-WAL.patch | text/x-patch | 7.8 KB |
| v12-0003-Provide-XLogReadAhead-to-decode-future-WAL-recor.patch | text/x-patch | 60.0 KB |
| v12-0004-Prefetch-referenced-blocks-during-recovery.patch | text/x-patch | 63.9 KB |
| v12-0005-WIP-Avoid-extra-buffer-lookup-when-prefetching-W.patch | text/x-patch | 10.7 KB |
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