Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752850AbZFHRzo (ORCPT ); Mon, 8 Jun 2009 13:55:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752108AbZFHRzf (ORCPT ); Mon, 8 Jun 2009 13:55:35 -0400 Received: from mk-filter-3-a-1.mail.uk.tiscali.com ([212.74.100.54]:36662 "EHLO mk-filter-3-a-1.mail.uk.tiscali.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750853AbZFHRzf (ORCPT ); Mon, 8 Jun 2009 13:55:35 -0400 X-Trace: 208684911/mk-filter-3.mail.uk.tiscali.com/B2C/$b2c-THROTTLED-DYNAMIC/b2c-CUSTOMER-DYNAMIC-IP/80.41.38.33/None/hugh.dickins@tiscali.co.uk X-SBRS: None X-RemoteIP: 80.41.38.33 X-IP-MAIL-FROM: hugh.dickins@tiscali.co.uk X-SMTP-AUTH: X-MUA: X-IP-BHB: Once X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Aq0GAI/tLEpQKSYh/2dsb2JhbACBT4xtAb9vhAoF X-IronPort-AV: E=Sophos;i="4.41,325,1241391600"; d="scan'208";a="208684911" Date: Mon, 8 Jun 2009 18:44:48 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@sister.anvils To: Arjan van de Ven cc: Ingo Molnar , linux-kernel@vger.kernel.org Subject: [PATCH] latencytop: note task_struct bloat Message-ID: 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: 1398 Lines: 31 Add belated comment to LATENCYTOP help text, making clear that this is a much more expensive option than you might think: along with the options it selects, it may add more than 4000 bytes to each struct task_struct (on 64-bit; more than 2000 on 32-bit), effectively quadrupling the size of an otherwise lean task_struct (in fact, slab on x86_64 fits only 1 in two pages, whereas it fits 5 in two pages without LATENCYTOP=y). Signed-off-by: Hugh Dickins --- lib/Kconfig.debug | 4 ++++ 1 file changed, 4 insertions(+) --- 2.6.30-rc8/lib/Kconfig.debug 2009-05-16 10:26:16.000000000 +0100 +++ linux/lib/Kconfig.debug 2009-06-08 18:30:50.000000000 +0100 @@ -826,6 +826,10 @@ config LATENCYTOP Enable this option if you want to use the LatencyTOP tool to find out which userspace is blocking on what kernel operations. + Note: enabling this option may add more than 4000 bytes to each + task_struct on a 64-bit kernel (more than 2000 bytes to task_struct + on a 32-bit kernel), multiplying its memory usage by 4 or even 5. + config SYSCTL_SYSCALL_CHECK bool "Sysctl checks" depends on SYSCTL_SYSCALL -- 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/