On Mon, 29 Jan 2007 17:49:14 -0800 "Martin J. Bligh" <[EMAIL PROTECTED]> wrote:
> Andrew Morton wrote: > > On Mon, 29 Jan 2007 17:31:20 -0800 > > "Martin J. Bligh" <[EMAIL PROTECTED]> wrote: > > > >> Peter Zijlstra wrote: > >>> On Sun, 2007-01-28 at 14:29 -0800, Andrew Morton wrote: > >>> > >>>> As Christoph says, it's very much preferred that code be migrated over to > >>>> kmap_atomic(). Partly because kmap() is deadlockable in situations > >>>> where a > >>>> large number of threads are trying to take two kmaps at the same time and > >>>> we run out. This happened in the past, but incidences have gone away, > >>>> probably because of kmap->kmap_atomic conversions. > >>>> From which callsite have you measured problems? > >>> CONFIG_HIGHPTE code in -rt was horrid. I'll do some measurements on > >>> mainline. > >>> > >> CONFIG_HIGHPTE is always horrid -we've known that for years. > > > > We have? What's wrong with it? <looks around for bug reports> > > http://www.ussg.iu.edu/hypermail/linux/kernel/0307.0/0463.html 2% overhead for a pte-intensive workload for unknown reasons four years ago. Sort of a mini-horrid, no? 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. - 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/
