Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752289AbbHCCYG (ORCPT ); Sun, 2 Aug 2015 22:24:06 -0400 Received: from mail-pa0-f42.google.com ([209.85.220.42]:36521 "EHLO mail-pa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750924AbbHCCYE convert rfc822-to-8bit (ORCPT ); Sun, 2 Aug 2015 22:24:04 -0400 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2098\)) Subject: Re: [PATCH v2] kthread: Export kthread functions From: yalin wang In-Reply-To: <20150801133221.GA6603@neilslaptop.think-freely.org> Date: Mon, 3 Aug 2015 10:23:56 +0800 Cc: Thomas Gleixner , Andrew Morton , David Kershner , tj@kernel.org, laijs@cn.fujitsu.com, nacc@linux.vnet.ibm.com, mingo@redhat.com, open list , jes.sorensen@redhat.com, sparmaintainer@unisys.com Content-Transfer-Encoding: 8BIT Message-Id: References: <1437777920-31156-1-git-send-email-david.kershner@unisys.com> <1438099141-8614-1-git-send-email-david.kershner@unisys.com> <20150728142748.a756d7540ad5cdaf4c9efc9e@linux-foundation.org> <20150730120223.GA27430@hmsreliant.think-freely.org> <6440C9D8-37D8-4E30-89D7-04CB96BC8114@gmail.com> <20150801133221.GA6603@neilslaptop.think-freely.org> To: Neil Horman X-Mailer: Apple Mail (2.2098) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2383 Lines: 83 > On Aug 1, 2015, at 21:32, Neil Horman wrote: > > On Sat, Aug 01, 2015 at 03:12:42PM +0800, yalin wang wrote: >> >>> 在 2015年7月31日，22:14，Thomas Gleixner 写道： >>> >>> >>> On Fri, 31 Jul 2015, Thomas Gleixner wrote: >>> >>>> On Fri, 31 Jul 2015, yalin wang wrote: >>>>> it is optimised to 2 instructions , >>>>> >>>>> this is my patch, hope can be merged : >>>> >>>> We are not exposing the internals of kthread management. Period. >>> >>> And your 'optimization' is completely bogus: >>> >>> Before your modification: >>> >>> size kernel/built-in.o >>> >>> text data bss dec hex filename >>> 1091514 141498 341928 1574940 18081c ../build/kernel/built-in.o >>> >>> After: >>> >>> text data bss dec hex filename >>> 1091664 141498 341928 1575090 1808b2 ../build/kernel/built-in.o >>> >>> That's an increase of text size by 150 byte. Interesting optimization. >>> >>> Thanks, >>> >>> tglx >>> >>> >> strange, this is my test result: >> >> size built-in.o* >> text data bss dec hex filename >> 743937 50786 56008 850731 cfb2b built-in.o // with the patch >> 744069 50786 56008 850863 cfbaf built-in.o_old // with out the patch >> > So you're willing to expose the internals of kthread_park in exchange for the > hope of saving 132 bytes of text. > > Thats just dumb. I agree with tglx, this shouldn't change. > > Neil not just size, mainly for performance, without inline: ffffffc0000d26b0: 97fff4aa bl ffffffc0000cf958 ffffffc0000d26b4: 53001c00 uxtb w0, w0 if kthread_should_park() inline: ffffffc0000d1a44: f85c8020 ldr x0, [x1,#-56] // kthread_should_park line ffffffc0000d1a48: 36100300 tbz w0, #2, ffffffc0000d1aa8 // kthread_should_park line still use 2 instructions, but don’t need a function call, maybe can do more optimisation by gcc sometimes . Anyway, this is just a suggest, it is up to you apply it or not. :) Thanks -- 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/