Yet more "preloading"

[Alexander Kellett]

On Fri, 19 Mar 2004 16:12:39 +0100 (CET), Michael Matz <matz at kde.org> 
wrote:
> Andrew had explained it in the message.  A kernel module will dump
> information about which blocks of which files are currently loaded in the
> page cache.

to be most optimal this must be run fairly frequently maybe
even based on system configuration changes, e.g, upgrading a
package could trigger a invalidation of the block lists. actually
this is silly, the solution that andrew proposes is so optimal
and efficient (well, at least, i assume so :)) that it can
easily be done on every bootup.

> You can then interpret this information, order the blocks sequentially 
> and them mmap the files in order, and touch pages in order to reproduce
> exactly the same (well, similar) pagecache, but faster due to no
> unnecessary seeks.  When thinking about this in the past this solution
> never occured to me (but then, I'm not kernel hacker ;) ).  I usually
> thought about some mean to dump the pages as they are read in from the
> disk (somehow with file information).  Simply dumping the filled 
> pagecache looks more elegant ;-)

nod. but, its still non optimal.

a truely optimised system like that of xp should also be
reordering the blocks on disk optimally as in the case of
config files and libs on devel systems i imagine there is a
lot of fragmention and seek times are really the killer here.

the link that akpm gave had an interesting reply saying that
it could be possible to use the swap space  for this, sounds
silly but if the swap ain't being used anyway (which is almost
always the case on a desktop system), i don't see why not
in fact i think this suggestion is pretty darn nifty :)
of course, this requires major help from the kernel. but then
the early solution does also and its not nearly so optimal.

chatting to hans reiser at linuxtag last year he seemed
to think that having reiser4 doing optimisation based on
system feedback wouldn't be too far out of the realms
of the possible.

i'd imagine full from cold machine to desktop bootup
within 30 seconds ain't really completely unrealistic
for a modern machine.

mvg,
Alex

-- 
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/