From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755075Ab1ATD0L (ORCPT ); Wed, 19 Jan 2011 22:26:11 -0500 Received: from smtp.polymtl.ca ([132.207.4.11]:57258 "EHLO smtp.polymtl.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754959Ab1ATD0I (ORCPT ); Wed, 19 Jan 2011 22:26:08 -0500 Message-Id: <20110120032557.188899549@efficios.com> User-Agent: quilt/0.48-1 Date: Wed, 19 Jan 2011 22:17:32 -0500 From: Mathieu Desnoyers To: LKML , David Miller , Steven Rostedt , Frederic Weisbecker , Ingo Molnar Cc: Mathieu Desnoyers Subject: [patch 3/3] tracepoints: use __u64_packed_aligned() as type and variable attribute References: <20110120031729.055590217@efficios.com> Content-Disposition: inline; filename=tracepoints-use-u64-packed-aligned-as-type-and-variable-attribute.patch X-Poly-FromMTA: (test.dorsal.polymtl.ca [132.207.72.60]) at Thu, 20 Jan 2011 03:25:57 +0000 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org commit 7e066fb870fcd1025ec3ba7bbde5d541094f4ce1 added the aligned(32) type and variable attribute to the tracepoint structures to deal with gcc happily aligning statically defined structures on 32-byte multiples. Working on issues within Ftrace, we came up with __64_packed_aligned, which deals with this issue more elegantly by forcing an 8-byte alignment to both the type declaration and variable definition. This therefore saves space, bringing down the size of struct tracepoint from 64 bytes to 38 on 64-bit architectures. Updating: - The type attribute (for iteration over the struct tracepoint array) - Added the variable attribute to the extern definition (needed to force gcc to consider this alignment for the following definition) - The definition variable attribute (to force gcc to this specific alignment for the static definitions) - The linker script (8-byte alignment can now replace the previous 32-byte alignment for the custom tracepoint section) Signed-off-by: Mathieu Desnoyers CC: David Miller CC: Steven Rostedt CC: Frederic Weisbecker CC: Ingo Molnar --- include/asm-generic/vmlinux.lds.h | 2 +- include/linux/tracepoint.h | 12 ++++-------- 2 files changed, 5 insertions(+), 9 deletions(-) Index: linux-2.6-lttng/include/asm-generic/vmlinux.lds.h =================================================================== --- linux-2.6-lttng.orig/include/asm-generic/vmlinux.lds.h +++ linux-2.6-lttng/include/asm-generic/vmlinux.lds.h @@ -168,7 +168,7 @@ CPU_KEEP(exit.data) \ MEM_KEEP(init.data) \ MEM_KEEP(exit.data) \ - . = ALIGN(32); \ + U64_ALIGN(); \ VMLINUX_SYMBOL(__start___tracepoints) = .; \ *(__tracepoints) \ VMLINUX_SYMBOL(__stop___tracepoints) = .; \ Index: linux-2.6-lttng/include/linux/tracepoint.h =================================================================== --- linux-2.6-lttng.orig/include/linux/tracepoint.h +++ linux-2.6-lttng/include/linux/tracepoint.h @@ -33,12 +33,7 @@ struct tracepoint { void (*regfunc)(void); void (*unregfunc)(void); struct tracepoint_func *funcs; -} __attribute__((aligned(32))); /* - * Aligned on 32 bytes because it is - * globally visible and gcc happily - * align these on the structure size. - * Keep in sync with vmlinux.lds.h. - */ +} __u64_packed_aligned; /* * Connect a probe to a tracepoint. @@ -143,7 +138,7 @@ static inline void tracepoint_update_pro * structure. Force alignment to the same alignment as the section start. */ #define __DECLARE_TRACE(name, proto, args, data_proto, data_args) \ - extern struct tracepoint __tracepoint_##name; \ + extern struct tracepoint __u64_aligned __tracepoint_##name; \ static inline void trace_##name(proto) \ { \ JUMP_LABEL(&__tracepoint_##name.state, do_trace); \ @@ -174,7 +169,8 @@ do_trace: \ static const char __tpstrtab_##name[] \ __attribute__((section("__tracepoints_strings"))) = #name; \ struct tracepoint __tracepoint_##name \ - __attribute__((section("__tracepoints"), aligned(32))) = \ + __u64_aligned \ + __attribute__((section("__tracepoints"))) = \ { __tpstrtab_##name, 0, reg, unreg, NULL }; #define DEFINE_TRACE(name) \