Re: [Lse-tech] Re: 10.31 second kernel compile

Mike Fedyk
2002-03-18T01:40:09Z

On Sun, Mar 17, 2002 at 05:13:16PM -0800, Davide Libenzi wrote:
> On Sun, 17 Mar 2002, Rik van Riel wrote:
>
> > On Sun, 17 Mar 2002, Davide Libenzi wrote:
> > > On Sun, 17 Mar 2002, Linus Torvalds wrote:
> > >
> > > > In article <Pine.LNX.4.44L.0203171021090.2181-100000@imladris.surriel.com>,
> > > > Rik van Riel <riel@conectiva.com.br> wrote:
> > > > >
> > > > >In other words, large pages should be a "special hack" for
> > > > >special applications, like Oracle and maybe some scientific
> > > > >calculations ?
> > > >
> > > > Yes, I think so.
> >
> > > Couldn't we choose the page size depending on the map size ?
> >
> > For on-disk files I guess this is better an mmap flag,
> > but for shared memory segments we could try to do this
> > automagically.
>
> What's the reason that would make more convenient for us, upon receiving a
> request to map a NNN MB file, to map it using 4Kb pages instead of 4MB ones ?

... the VM chooses to unmap a mmaped page, it chooses a 4mb page, later it
needs just a few bytes from that unmaped page and free 4mb instead of 4kb (worst
case) to map that page again...