2011/1/11 Garick Hamlin <gham...@isc.upenn.edu>: > On Mon, Jan 10, 2011 at 09:09:28AM -0500, Magnus Hagander wrote: >> On Sun, Jan 9, 2011 at 23:33, Cédric Villemain >> <cedric.villemain.deb...@gmail.com> wrote: >> > 2011/1/7 Magnus Hagander <mag...@hagander.net>: >> >> On Fri, Jan 7, 2011 at 01:47, Cédric Villemain >> >> <cedric.villemain.deb...@gmail.com> wrote: >> >>> 2011/1/5 Magnus Hagander <mag...@hagander.net>: >> >>>> On Wed, Jan 5, 2011 at 22:58, Dimitri Fontaine <dimi...@2ndquadrant.fr> >> >>>> wrote: >> >>>>> Magnus Hagander <mag...@hagander.net> writes: >> >>>>>> * Stefan mentiond it might be useful to put some >> >>>>>> posix_fadvise(POSIX_FADV_DONTNEED) >> >>>>>> in the process that streams all the files out. Seems useful, as >> >>>>>> long as that >> >>>>>> doesn't kick them out of the cache *completely*, for other backends >> >>>>>> as well. >> >>>>>> Do we know if that is the case? >> >>>>> >> >>>>> Maybe have a look at pgfincore to only tag DONTNEED for blocks that are >> >>>>> not already in SHM? >> >>>> >> >>>> I think that's way more complex than we want to go here. >> >>>> >> >>> >> >>> DONTNEED will remove the block from OS buffer everytime. >> >> >> >> Then we definitely don't want to use it - because some other backend >> >> might well want the file. Better leave it up to the standard logic in >> >> the kernel. >> > >> > Looking at the patch, it is (very) easy to add the support for that in >> > basebackup.c >> > That supposed allowing mincore(), so mmap(), and so probably switch >> > the fopen() to an open() (or add an open() just for mmap >> > requirement...) >> > >> > Let's go ? >> >> Per above, I still don't think we *should* do this. We don't want to >> kick things out of the cache underneath other backends, and since we >> can't control that. Either way, it shouldn't happen in the beginning, >> and if it does, should be backed with proper benchmarks. > > Another option that occurs to me is an option to use direct IO (or another > means as needed) to bypass the cache. So rather than kicking it out of > the cache, we attempt just not to pollute the cache by bypassing it for cold > pages and use either normal io for 'hot pages', or use a 'read()' to "heat" > the cache afterward.
AFAIR, even Linus is rejecting the idea to use it seriously, except if I shuffle in my memory. > > Garick > >> >> I've committed the backend side of this, without that. Still working >> on the client, and on cleaning up Heikki's patch for grammar/parser >> support. >> >> -- >> Magnus Hagander >> Me: http://www.hagander.net/ >> Work: http://www.redpill-linpro.com/ >> >> -- >> Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) >> To make changes to your subscription: >> http://www.postgresql.org/mailpref/pgsql-hackers > -- Cédric Villemain 2ndQuadrant http://2ndQuadrant.fr/ PostgreSQL : Expertise, Formation et Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
