| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Sean Chittenden <seanc(at)joyent(dot)com> |
| Subject: | Re: WAL prefetch |
| Date: | 2018-06-18 20:44:09 |
| Message-ID: | CA+TgmoYk=jPktH6x2P=_fagHGNrcooU3sku=sW+_7iNHTYWvBA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Jun 16, 2018 at 3:41 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> The posix_fadvise approach is not perfect, no doubt about that. But it
>> works pretty well for bitmap heap scans, and it's about 13249x better
>> (rough estimate) than the current solution (no prefetching).
>
> Sure, but investing in an architecture we know might not live long also
> has it's cost. Especially if it's not that complicated to do better.
My guesses are:
- Using OS prefetching is a very small patch.
- Prefetching into shared buffers is a much bigger patch.
- It'll be five years before we have direct I/O.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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