On 1 November 2017 at 11:49, Andres Freund <andres@anarazel.de> wrote:
> Right. It'd probably be good to be a bit more adaptive here. But it's
> hard to do with posix_fadvise - we'd need an operation that actually
> notifies us of IO completion. If we were using, say, asynchronous
> direct IO, we could initiate the request and regularly check how many
> blocks ahead of the current window are already completed and adjust the
> queue based on that, rather than jus tfiring off fadvises and hoping for
> the best.
In case it's of interest, I did some looking into using Linux's AIO
support in Pg a while ago, when chasing some issues around fsync
retries and handling of I/O errors.
It was a pretty serious dead end; it was clear that fsync support in
AIO is not only incomplete but inconsistent across kernel versions,
let alone other platforms.
But I see your name in the relevant threads, so you know that. To save
others the time, see:
* https://lwn.net/Articles/724198/
* https://lwn.net/Articles/671649/
-- Craig Ringer http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
