From: Scott Wood <scottwood@freescale•com>
To: David Miller <davem@davemloft•net>
Cc: proski@gnu•org, a.p.zijlstra@chello•nl, sandmann@redhat•com,
pq@iki•fi, linux-kernel@vger•kernel.org, rostedt@goodmis•org,
linuxppc-dev@ozlabs•org, srostedt@redhat•com, paulus@samba•org,
mingo@elte•hu
Subject: Re: [PATCH 2/2] ftrace: support for PowerPC
Date: Thu, 15 May 2008 11:48:02 -0500 [thread overview]
Message-ID: <20080515164802.GA2664@loki.buserror.net> (raw)
In-Reply-To: <20080514.222857.246967279.davem@davemloft.net>
On Wed, May 14, 2008 at 10:28:57PM -0700, David Miller wrote:
> From: Steven Rostedt <rostedt@goodmis•org>
> Date: Wed, 14 May 2008 23:49:44 -0400
>
> > +#ifdef CONFIG_FTRACE
> > +#ifdef CONFIG_DYNAMIC_FTRACE
> > +_GLOBAL(mcount)
> > +_GLOBAL(_mcount)
> > + stwu r1,-48(r1)
> > + stw r3, 12(r1)
> > + stw r4, 16(r1)
> > + stw r5, 20(r1)
> > + stw r6, 24(r1)
> > + mflr r3
> > + stw r7, 28(r1)
> > + mfcr r5
> > + stw r8, 32(r1)
> > + stw r9, 36(r1)
> > + stw r10,40(r1)
> > + stw r3, 44(r1)
> > + stw r5, 8(r1)
>
> Yikes, that's really expensive.
>
> Can't you do a tail call and let the function you end
> up calling do all the callee-saved register pops onto
> the stack?
The PPC32 ABI seems to (unfortunately) suggest that, with mcount, all
registers are callee-saved (except for the modifiable-during-function-linkage
registers like r0, r11, and r12) -- so mcount has to save the registers that
the callee won't (because they're normally volatile).
-Scott
next prev parent reply other threads:[~2008-05-15 16:49 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-15 3:49 [PATCH 0/2] ftrace ported to PPC Steven Rostedt
2008-05-15 3:49 ` [PATCH 1/2] ftrace ppc: add irqs_disabled_flags to ppc Steven Rostedt
2008-05-16 12:05 ` Ingo Molnar
2008-05-15 3:49 ` [PATCH 2/2] ftrace: support for PowerPC Steven Rostedt
2008-05-15 5:28 ` David Miller
2008-05-15 13:38 ` Steven Rostedt
2008-05-15 16:48 ` Scott Wood [this message]
2008-05-16 12:06 ` Ingo Molnar
2008-05-20 14:04 ` Michael Ellerman
2008-05-20 14:17 ` Benjamin Herrenschmidt
2008-05-20 14:51 ` Steven Rostedt
2008-05-20 14:32 ` Steven Rostedt
2008-05-22 18:31 ` [PATCH] ftrace: powerpc clean ups Steven Rostedt
2008-05-27 15:36 ` Thomas Gleixner
2008-06-02 2:15 ` Michael Ellerman
2008-05-15 4:40 ` [PATCH 0/2] ftrace ported to PPC Paul Mackerras
2008-05-16 12:05 ` Ingo Molnar
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