From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx120.postini.com [74.125.245.120]) by kanga.kvack.org (Postfix) with SMTP id 27C476B0044 for ; Wed, 26 Sep 2012 19:50:46 -0400 (EDT) Date: Wed, 26 Sep 2012 16:50:44 -0700 From: Andrew Morton Subject: Re: Please be aware that __always_inline doesn't mean "always inline"! Message-Id: <20120926165044.46b8f7d6.akpm@linux-foundation.org> In-Reply-To: <50638DCC.5040506@att.net> References: <50638DCC.5040506@att.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Daniel Santos Cc: Daniel Santos , LKML , linux-mm@kvack.org, torvalds@linux-foundation.org On Wed, 26 Sep 2012 18:20:44 -0500 Daniel Santos wrote: > I've noticed that there's a lot of misperception about the meaning of > the __always_inline, or more specifically, > __attribute__((always_inline)), which does not actually cause the > function to always be inlined. Rather, it *allows* gcc to inline the > function, even when compiling without optimizations. Here is the > description of the attribute from gcc's docs > (http://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Function-Attributes.html) > > always_inline > Generally, functions are not inlined unless optimization is specified. > For functions declared inline, this attribute inlines the function even > if no optimization level was specified. > > This would even appear to imply that such functions aren't even marked > as "inline" (something I wasn't aware of until today). The only > mechanism I'm currently aware of to force gcc to inline a function is > the flatten attribute (see https://lkml.org/lkml/2012/9/25/643) which > works backwards, you declare it on the calling function, and it forces > gcc to inline all functions (marked as inline) that it calls. As I mentioned in the other thread, the __always_inline's in fs/namei.c (at least) are doing exactly what we want them to do, so some more investigation is needed here? -- 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