(2013/12/11 10:25), Tom Lane wrote: > Jeff Janes <jeff.ja...@gmail.com> writes: >> On Tue, Dec 3, 2013 at 11:39 PM, Claudio Freire >> <klaussfre...@gmail.com>wrote: >>> Problem is, Postgres relies on a working kernel cache for checkpoints. >>> Checkpoint logic would have to be heavily reworked to account for an >>> impaired kernel cache. > >> I don't think it would need anything more than a sorted checkpoint. > > Nonsense. We don't have access to the physical-disk-layout information > needed to do reasonable sorting; OS knows physical-disk-layout which is under following. > [mitsu-ko@ssd ~]$ filefrag -v .bashrc > Filesystem type is: ef53 > File size of .bashrc is 124 (1 block, blocksize 4096) > ext logical physical expected length flags > 0 0 15761410 1 eof > .bashrc: 1 extent found If we have to know this information, we can get physical-disk-layout whenever.
> to say nothing of doing something > intelligent in a multi-spindle environment, or whenever any other I/O > is going on concurrently. IO scheduler in OS knows it best. So I think BufferedIO is faster than DirectIO in general situations. Regards, -- Mitsumasa KONDO NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
