From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030301Ab3BGV6v (ORCPT ); Thu, 7 Feb 2013 16:58:51 -0500 Received: from mga01.intel.com ([192.55.52.88]:52856 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030217Ab3BGV6u (ORCPT ); Thu, 7 Feb 2013 16:58:50 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,623,1355126400"; d="scan'208";a="284197096" From: Andi Kleen To: mmarek@suse.cz Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Andi Kleen Subject: [PATCH] Kbuild: Disable var tracking with CONFIG_DEBUG_INFO_REDUCED Date: Thu, 7 Feb 2013 13:58:40 -0800 Message-Id: <1360274320-26833-1-git-send-email-andi@firstfloor.org> X-Mailer: git-send-email 1.7.7.6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andi Kleen Newer gcc enables the var-tracking pass with -g to keep track which registers contain which variables. This is one of the slower passes in gcc. With reduced debug info (aimed at objdump -S, but not using a full debugger) we don't need this fine grained tracking. But it was still enabled because -g was enabled. Disable it explicitely for DEBUG_INFO_REDUCED. On my 8T workstation this gives me about a 12 second gain in building a reasonable kernel config (2min16 vs 2min28) with DEBUG_INFO_REDUCED. With full DEBUG_INFO it takes 2min46 The actual improvement in user time taken by the compiler is much higher (all CPU combined user time 15min5s vs 16m30 before) but the usual amdahl bottleneck on the linker prevents more speedup. It still saves some more energy and keeps cycles for other things. Signed-off-by: Andi Kleen --- Makefile | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/Makefile b/Makefile index 54dfde5..7e423df 100644 --- a/Makefile +++ b/Makefile @@ -619,7 +619,8 @@ KBUILD_AFLAGS += -gdwarf-2 endif ifdef CONFIG_DEBUG_INFO_REDUCED -KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) +KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \ + $(call cc-option,-fno-var-tracking) endif ifdef CONFIG_FUNCTION_TRACER -- 1.7.7.6