Arjan van de Ven wrote:
>
> On Tue, Mar 05, 2002 at 07:26:04PM +0100, Andrea Arcangeli wrote:
>
> > Another approch would be to add the pages backing the bh into the lru
> > too, but then we'd need to mess with the slab and new bitflags, new
> > methods and so I don't think it's the best solution. The only good
> > reason for putting new kind of entries in the lru would be to age them
> > too the same way as the other pages, but we don't need that with the bh
> > (they're just in, and we mostly care only about the page age, not the bh
> > age).
>
> For 2.5 I kind of like this idea. There is one issue though: to make
> this work really well we'd probably need a ->prepareforfreepage()
> or similar page op (which for page cache pages can be equal to writepage()
> ) which the vm can use to prepare this page for freeing.
If we stop using buffer_heads for pagecache I/O, we don't have this problem.
I'm showing a 20% reduction in CPU load for large reads. Which is a *lot*,
given that read load is dominated by copy_to_user.
2.5 is significantly less efficient than 2.4 at this time. Some of that
seems to be due to worsened I-cache footprint, and a lot of it is due
to the way buffer_heads now have a BIO wrapper layer.
Take a look at submit_bh(). The writing is on the wall, guys.
-
-
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 Mar 07 2002 - 21:00:45 EST