On Tue, Jan 30, 2007 at 05:11:32PM -0800, Andrew Morton wrote:
> On Wed, 31 Jan 2007 11:44:36 +1100
> David Chinner <[email protected]> wrote:
>
> > On Mon, Jan 29, 2007 at 06:15:57PM -0800, Andrew Morton wrote:
> > > We still don't know what is the source of kmap() activity which
> > > necessitated this patch btw. AFAIK the busiest source is ext2 directories,
> > > but perhaps NFS under certain conditions?
> > >
> > > <looks at xfs_iozero>
> > >
> > > ->prepare_write no longer requires that the caller kmap the page.
> >
> > Agreed, but don't we (xfs_iozero) have to map it first to zero it?
> >
> > I think what you are saying here, Andrew, is that we can
> > do something like:
> >
> > page = grab_cache_page
> > ->prepare_write(page)
> > kaddr = kmap_atomic(page, KM_USER0)
> > memset(kaddr+offset, 0, bytes)
> > flush_dcache_page(page)
> > kunmap_atomic(kaddr, KM_USER0)
> > ->commit_write(page)
> >
> > to avoid using kmap() altogether?
>
> Yup. Even better, use clear_highpage().
For even more goodness, clearmem_highpage_flush() does exactly
the right thing for partial page zeroing ;)
Thanks, Andrew, I've added a patch to my QA tree with this mod.
Cheers,
Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
