On Mon, 14 Jun 2010, James Bottomley wrote:
> On Mon, 2010-06-14 at 18:21 -0400, Tim Abbott wrote:
> > On Mon, 14 Jun 2010, Matt Fleming wrote:
> >
> > > Do these special kernel sections include things like the parisc
> > > .text.do_softirq, .text.sys_exit, etc? James raised a good objection to
> > > the parisc patch of this series. I'm guessing most people saw it already
> > > but I'll paste it here for reference,
> > >
> > > This would destroy all of the named parisc text ordering we do above the
> > > removed line because now you'd have swept up all the function sections
> > > before we get to them, won't it?
> > >
> > > The ordering is an execution speed up on 32 bit systems because our
> > > relative jump is so short.
> > >
> > > Will you changes handle this OK?
> >
> > I think I addressed this in my reply to James just now, but to be super
> > clear, this -ffunction-sections plan involves renaming .text.do_softirq to
> > .text..do_softirq (etc.) first.
>
> OK, so that doesn't make a lot of sense to me; I suspect because you
> don't understand what parisc is doing. These aren't names of linux
> special sections ... they're names of function sections. For
> efficiency, we take specific hot functions and place them together in
> the linker script so the jumps between them are small enough to be coded
> as relative on the 32 bit architecture. It's really just a more
> efficient way of laying out the binary.
Yeah, I'd forgotten parisc was doing -ffunction-sections, now I understand
what you're talking about. What I'd recommend is just moving the
.text.do_softirq and friends like in the hunk below -- I believe that
should achieve the same performance goals, and should have no conflict
with adding a wildcard for -ffunction-sections generated sections to
TEXT_TEXT.
-Tim Abbott
diff --git a/arch/parisc/kernel/vmlinux.lds.S
b/arch/parisc/kernel/vmlinux.lds.S
index d64a6bb..ad0d3d3 100644
--- a/arch/parisc/kernel/vmlinux.lds.S
+++ b/arch/parisc/kernel/vmlinux.lds.S
@@ -52,15 +52,15 @@ SECTIONS
_text = .; /* Text and read-only data */
.text ALIGN(16) : {
HEAD_TEXT
+ *(.text.do_softirq)
+ *(.text.sys_exit)
+ *(.text.do_sigaltstack)
+ *(.text.do_fork)
TEXT_TEXT
SCHED_TEXT
LOCK_TEXT
KPROBES_TEXT
IRQENTRY_TEXT
- *(.text.do_softirq)
- *(.text.sys_exit)
- *(.text.do_sigaltstack)
- *(.text.do_fork)
*(.text.*)
*(.fixup)
*(.lock.text) /* out-of-line lock text */
--
To unsubscribe from this list: send the line "unsubscribe linux-arch" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
