lkml.org 
[lkml]   [2001]   [Oct]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: broken VM in 2.4.10-pre9


On Thu, 27 Sep 2001, Pavel Machek wrote:

> Hi!
>
> > > > > So my suggestion was to look at getting anonymous pages backed by what
> > > > > amounts to a shared memory segment. In that vein. By using an extent
> > > > > based data structure we can get the cost down under the current 8 bits
> > > > > per page that we have for the swap counts, and make allocating swap
> > > > > pages faster. And we want to cluster related swap pages anyway so
> > > > > an extent based system is a natural fit.
> > > >
> > > > Much of this goes away if you get rid of both the swap and anonymous page
> > > > special cases. Back anonymous pages with the "whoops everything I write here
> > > > vanishes mysteriously" file system and swap with a swapfs
> > >
> > > What exactly is anonymous memory? I thought it is what you do when you
> > > want to malloc(), but you want to back that up by swap, not /dev/null.
> >
> > Anonymous memory is memory which is not backed by a filesystem or a
> > device. eg: malloc()ed memory, shmem, mmap(MAP_PRIVATE) on a file (which
> > will create anonymous memory as soon as the program which did the mmap
> > writes to the mapped memory (COW)), etc.
>
> So... how can alan propose to back anonymous memory with /dev/null?

I guess he means anonymous memory backed up by /dev/null means anonymous
memory backep up by nothing.

> [see above] It should be backed by swap, no?

Not necessarily. As soon as we need to swapout anon memory, we have to
back it up by swap. (mm/vmscan.c:try_to_swap_out() job)

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:17    [W:0.083 / U:1.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site