Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: [PATCH] Radix-tree pagecache for 2.5 | Date | Wed, 6 Feb 2002 10:07:02 +0100 |
| |
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/
| |