Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754684AbZG0Uo2 (ORCPT ); Mon, 27 Jul 2009 16:44:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754595AbZG0Uo1 (ORCPT ); Mon, 27 Jul 2009 16:44:27 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:58727 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754583AbZG0Uo1 (ORCPT ); Mon, 27 Jul 2009 16:44:27 -0400 Date: Mon, 27 Jul 2009 16:44:24 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: John Reiser cc: Steven Rostedt , Ingo Molnar , Sam Ravnborg , Tejun Heo , Frederic Weisbecker , Li Zefan , Linux Kernel Mailing List Subject: Re: ftrace: __start_mcount_loc should be .init.rodata In-Reply-To: <4A6DF0B6.7080402@bitwagon.com> Message-ID: References: <4A6DF0B6.7080402@bitwagon.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2491 Lines: 75 On Mon, 27 Jul 2009, John Reiser wrote: > __start_mcount_loc[] is unused after init, yet occupies RAM forever > as part of .rodata. 152kiB is typical on a 64-bit architecture. Instead, > __start_mcount_loc should be in the interval [__init_begin, __init_end) > so that the space is reclaimed after init. Are you sure about that? > > __start_mcount_loc[] is generated during the load portion > of kernel build, and is used only by ftrace_init(). ftrace_init is declared > '__init' and is in .init.text, which is freed after init. > __start_mcount_loc is placed into .rodata by a call to MCOUNT_REC inside > the RO_DATA macro of include/asm-generic/vmlinux.lds.h. The array *is* > read-only, but more importantly it is not used after init. So the call to > MCOUNT_REC should be moved from RO_DATA to INIT_DATA. > > This patch has been tested on x86_64 with CONFIG_DEBUG_PAGEALLOC=y > which verifies that the address range never is accessed after init. > > [Please cc: me if replying only to the linux-kernel list.] > > Signed off by: John Reiser > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index 6ad76bf..98b37cf 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -91,7 +91,8 @@ > #endif > > #ifdef CONFIG_FTRACE_MCOUNT_RECORD > -#define MCOUNT_REC() VMLINUX_SYMBOL(__start_mcount_loc) = .; \ > +#define MCOUNT_REC() . = ALIGN(8); \ > + VMLINUX_SYMBOL(__start_mcount_loc) = .; \ > *(__mcount_loc) \ > VMLINUX_SYMBOL(__stop_mcount_loc) = .; > #else > @@ -331,7 +332,6 @@ > /* __*init sections */ \ > __init_rodata : AT(ADDR(__init_rodata) - LOAD_OFFSET) { \ Isn't this in __init_rodata? Doesn't this get removed too? I may be confused by all the uses of "init" in this file. -- Steve > *(.ref.rodata) \ > - MCOUNT_REC() \ > DEV_KEEP(init.rodata) \ > DEV_KEEP(exit.rodata) \ > CPU_KEEP(init.rodata) \ > @@ -455,6 +455,7 @@ > MEM_DISCARD(init.data) \ > KERNEL_CTORS() \ > *(.init.rodata) \ > + MCOUNT_REC() \ > DEV_DISCARD(init.rodata) \ > CPU_DISCARD(init.rodata) \ > MEM_DISCARD(init.rodata) > > -- > > -- 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/