lkml.org 
[lkml]   [2002]   [Feb]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] Radix-tree pagecache for 2.5
Date
On February 5, 2002 07:45 pm, Rik van Riel wrote:
> On Tue, 5 Feb 2002, Pavel Machek wrote:
> > > > > the biggest reason for this is that we *suck* at readahead for
> > > > > mmap....
> > > >
> > > > Is there not also fault overhead and similar issues related to mmap(2)
> > > > in general, that are not present with read(2)/write(2)?
> > >
> > > If a fault is more expensive than a system call, we're doing
> > > something wrong in the page fault path ;)
> >
> > You can read 128K at a time, but you can't fault 128K...
>
> Why not ?
>
> If the pages are present (read-ahead) and the page table
> is present, I see no reason why we couldn't fill in 32
> page table entries at once.

Yes, essentially what you want is to schedule a generic_file_readahead, which
we'd need to cook up a mechanism for doing. The other part - much harder -
is deciding when to readahead, and how much.

I'd amend your original statement to just 'we *suck* at readahead'.

--
Daniel
-
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 13:24    [W:0.087 / U:0.244 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site