From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932636AbbJ0SN5 (ORCPT ); Tue, 27 Oct 2015 14:13:57 -0400 Received: from mail-wi0-f180.google.com ([209.85.212.180]:36260 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752300AbbJ0SN4 (ORCPT ); Tue, 27 Oct 2015 14:13:56 -0400 Date: Tue, 27 Oct 2015 19:13:51 +0100 From: Ingo Molnar To: Russell King - ARM Linux Cc: Peter Zijlstra , Arnd Bergmann , Liam Girdwood , linux-kernel@vger.kernel.org, Mark Brown , akpm@linux-foundation.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] mutex: make mutex_lock_nested an inline function Message-ID: <20151027181351.GA15015@gmail.com> References: <11282238.AHmyWliPRj@wuerfel> <20151013203812.GM17308@twins.programming.kicks-ass.net> <11817958.z9KtmeKzV7@wuerfel> <57854232.vMTrn4EgZx@wuerfel> <20151022150959.GU17308@twins.programming.kicks-ass.net> <20151022174400.GW32532@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151022174400.GW32532@n2100.arm.linux.org.uk> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Russell King - ARM Linux wrote: > On Thu, Oct 22, 2015 at 05:09:59PM +0200, Peter Zijlstra wrote: > > Hmm, I was sure I send a reply, but I cannot even find it in my own sent > > folder so who knows. > > > > My current preference is to keep the thing a macro and work around it in > > the usage site because while these warns are annoying, they're at least > > visible. Whereas, with an inline, code bloat is entirely silent. Even if > > the sites you found are harmless, there's no saying what the future will > > bring etc.. > > I agree - we've got way too many inline functions already. My biggest annoyance > in that respect is the asm-generic dma_map_single() implementation that we're > now forced to use on ARM, which results in quite a large chunk of code at every > callsite. > > The problem there is that when you have drivers which do something like: > > dma = dma_map_single(dev, page_address(page), size, dir); > > you end up with code which converts the struct page to a virtual address, and > then you end up with code in the dma_map_single() inline function which then > converts it back to a struct page + offset - none of which, with modern ARM > kernels, the compiler has a hope in hell of optimising. > > So we end up with all that junk at every single dma_map_single() callsite. If > dma_map_single() were a library function, it would be a lot smaller since we'd > only have one copy of the complex virt->struct page conversion. Should be pretty easy to fix, once you know which inline functions hurt. Thanks, Ingo