| From: | Cédric Villemain <cedric(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: checkpointer continuous flushing |
| Date: | 2015-06-08 07:45:06 |
| Message-ID: | 55754802.1050401@2ndQuadrant.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Le 07/06/2015 16:53, Fabien COELHO a écrit :
> +» » /*·Others:·say·that·data·should·not·be·kept·in·memory...
> +» » ·*·This·is·not·exactly·what·we·want·to·say,·because·we·want·to·write
> +» » ·*·the·data·for·durability·but·we·may·need·it·later·nevertheless.
> +» » ·*·It·seems·that·Linux·would·free·the·memory·*if*·the·data·has
> +» » ·*·already·been·written·do·disk,·else·it·is·ignored.
> +» » ·*·For·FreeBSD·this·may·have·the·desired·effect·of·moving·the
> +» » ·*·data·to·the·io·layer.
> +» » ·*/
> +» » rc·=·posix_fadvise(context->fd,·context->offset,·context->nbytes,
> +» » » » » » ···POSIX_FADV_DONTNEED);
> +
It looks a bit hazardous, do you have a benchmark for freeBSD ?
Sources says:
case POSIX_FADV_DONTNEED:
/*
* Flush any open FS buffers and then remove pages
* from the backing VM object. Using vinvalbuf() here
* is a bit heavy-handed as it flushes all buffers for
* the given vnode, not just the buffers covering the
* requested range.
--
Cédric Villemain +33 (0)6 20 30 22 52
http://2ndQuadrant.fr/
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