From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx151.postini.com [74.125.245.151]) by kanga.kvack.org (Postfix) with SMTP id ADEED6B0044 for ; Wed, 26 Sep 2012 17:42:20 -0400 (EDT) Date: Wed, 26 Sep 2012 14:42:19 -0700 From: Andrew Morton Subject: Re: [PATCH 05/10] mm, util: Use dup_user to duplicate user memory Message-Id: <20120926144219.bf4bfb9d.akpm@linux-foundation.org> In-Reply-To: References: <1347137279-17568-1-git-send-email-elezegarcia@gmail.com> <1347137279-17568-5-git-send-email-elezegarcia@gmail.com> <20120925142948.6b062cb6.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ezequiel Garcia Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Pekka Enberg On Tue, 25 Sep 2012 22:15:38 -0300 Ezequiel Garcia wrote: > > This patch increases util.o's text size by 238 bytes. A larger kernel > > with a worsened cache footprint. > > > > And we did this to get marginally improved tracing output? This sounds > > like a bad tradeoff to me. > > > > Mmm, that's bad tradeoff indeed. > It's certainly odd since the patch shouldn't increase the text size > *that* much. > Is it too much to ask that you send your kernel config and gcc version. x86_64 allmodconfig with CONFIG_DEBUG_INFO=n, CONFIG_ENABLE_MUST_CHECK=n. gcc-4.4.4. > My compilation (x86 kernel in gcc 4.7.1) shows a kernel less bloated: > > $ readelf -s util-dup-user.o | grep dup_user > 161: 00001c10 108 FUNC GLOBAL DEFAULT 1 memdup_user > 169: 00001df0 159 FUNC GLOBAL DEFAULT 1 strndup_user > $ readelf -s util.o | grep dup_user > 161: 00001c10 108 FUNC GLOBAL DEFAULT 1 memdup_user > 169: 00001df0 98 FUNC GLOBAL DEFAULT 1 strndup_user > > $ size util.o > text data bss dec hex filename > 18319 2077 0 20396 4fac util.o > $ size util-dup-user.o > text data bss dec hex filename > 18367 2077 0 20444 4fdc util-dup-user.o > > Am I doing anything wrong? Dunno - it could be a config thing. > If you still feel this is unnecessary bloatness, perhaps I could think of > something depending on CONFIG_TRACING (though I know > we all hate those nasty ifdefs). hm. Perhaps we could add an __always_inline_for_tracing. But that wouldn't help a lot - a CONFIG_TRACING_SUPPORT=y kernel would still be impacted even if the user is never using tracing. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org