Messages in this thread | | | Date | Wed, 29 May 2013 16:53:12 +0200 | From | Andres Freund <> | Subject | Re: [patch 1/2] mm: fincore() |
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On 2013-02-16 14:53:43 +1030, Rusty Russell wrote: > Andrew Morton <akpm@linux-foundation.org> writes: > > On Fri, 15 Feb 2013 18:13:04 -0500 > > Johannes Weiner <hannes@cmpxchg.org> wrote: > >> I dunno. The byte vector might not be optimal but its worst cases > >> seem more attractive, is just as extensible, and dead simple to use. > > > > But I think "which pages from this 4TB file are in core" will not be an > > uncommon usage, and writing a gig of memory to find three pages is just > > awful. > > Actually, I don't know of any usage for this call.
[months later, catching up]
I do. Postgres' could really use something like that for making saner assumptions about the cost of doing an index/heap scan. postgres doesn't use mmap() and mmaping larger files into memory isn't all that cheap (32bit...) so having fincore would be nice.
Greetings,
Andres Freund
-- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
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