> 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.
>
> Rik
Well, filling 32 page tables entries at once is certainly a big readahead...
for the common cases.
Maybe this high number could be a result of a madavise(..., MADV_SEQUENTIAL
or MAP_WILLNEED)
Solaris does exactly this kind of trick.
Eric
-
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/
This archive was generated by hypermail 2b29 : Thu Feb 07 2002 - 21:00:44 EST