From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FD106F305; Thu, 24 Oct 2024 06:57:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729753042; cv=none; b=HiocZ1XqOxqWt+Ekn8a9uQN64xWu8YEYA9XUNB+5VaCnn+UAPW4J2njTccvxc8BQ7eeEI216LezoSIm/Pd6aGah4exBHj7psRdK5D+Sx/n/hAC35ZmejVaOBxReEx0HxXC+rwV800WvxuEgYWM64cCKV77ssW6qCW7rYt2zgrpk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729753042; c=relaxed/simple; bh=HEG5AppcH8Omlqn6dqBEOOVtSw/qmfp62vOEhiOJa7A=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UTNB+O01MUT8MpNxedPvYkagmX3/4JMMdZnzuv5cO1H9i6vSGfSWLJ5HHFWiuJu7nhBUaQBsBzz1QpsLo6I0BciRlNVBv6VZhBxByfQMO0CXop8G6Q2lqjWQW6Ozh7uYuv/BEnu38hmNPVl2pCD+9TIjckmaTtJ3SXEYfIi8we8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Hbm0gELR; arc=none smtp.client-ip=192.198.163.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Hbm0gELR" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1729753040; x=1761289040; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=HEG5AppcH8Omlqn6dqBEOOVtSw/qmfp62vOEhiOJa7A=; b=Hbm0gELRY9GpkaKmeCP0QyJk7eorP/O3ys77suJrrdhhZ4YtXhN9AWsy LwNT8vfUGUC8GDhlavEMLfRd1iXQrmLeWpE+CE6cxeJWgfxd0bYgCd7nH 4duZ27uDopCXPVhu/3I+3uaZC7/1fsLrsx1YVtYJM6GCv7QRgphykizyU kXFyMyplwGEymG3ay8biAs7ouUN/RrUyqTrs+NtpibWq+krc4//00BW3h Xi8vBvOSegpIP+wOOMrReE3XhHutf2s3TI80DWdhGYKrvl4TbemYhD68k YhMomAp75HbH4HY9SAILMKFsWTxddn9cZL8MZ8/gmkmC/LvOQKIAQc2wK A==; X-CSE-ConnectionGUID: d5y5aeOGROiaYB9Wpg939w== X-CSE-MsgGUID: W8vsASeZRJqWL7X9OUxgmw== X-IronPort-AV: E=McAfee;i="6700,10204,11234"; a="39979952" X-IronPort-AV: E=Sophos;i="6.11,228,1725346800"; d="scan'208";a="39979952" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Oct 2024 23:57:19 -0700 X-CSE-ConnectionGUID: Sd9fHMOjSUOoo2kjypeU7g== X-CSE-MsgGUID: yNoH64OFRuW/PaET0dNstg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,228,1725346800"; d="scan'208";a="80160070" Received: from smile.fi.intel.com ([10.237.72.154]) by fmviesa007.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Oct 2024 23:57:16 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.98) (envelope-from ) id 1t3rmS-00000006Tym-1cq6; Thu, 24 Oct 2024 09:57:12 +0300 Date: Thu, 24 Oct 2024 09:57:12 +0300 From: Andy Shevchenko To: Dan Williams Cc: "Huang, Ying" , David Hildenbrand , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, Davidlohr Bueso , Jonathan Cameron , Alistair Popple , Bjorn Helgaas , Baoquan He , Dave Jiang , Alison Schofield Subject: Re: [RFC] resource: Avoid unnecessary resource tree walking in __region_intersects() Message-ID: References: <20241010065558.1347018-1-ying.huang@intel.com> <87set3a1nm.fsf@yhuang6-desk2.ccr.corp.intel.com> <671965a8b37a2_1bbc629489@dwillia2-xfh.jf.intel.com.notmuch> Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <671965a8b37a2_1bbc629489@dwillia2-xfh.jf.intel.com.notmuch> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo On Wed, Oct 23, 2024 at 02:07:52PM -0700, Dan Williams wrote: > Andy Shevchenko wrote: > > On Fri, Oct 11, 2024 at 09:06:37AM +0800, Huang, Ying wrote: > > > David Hildenbrand writes: > > > > On 10.10.24 08:55, Huang Ying wrote: ... > > > > for ((_p) = (_root)->child; (_p); (_p) = next_resource_XXX(_root, _p)) > > > > > > Yes. This can improve code readability. > > > > > > A possible issue is that "_root" will be evaluated twice in above macro > > > definition. IMO, this should be avoided. > > > > Ideally, yes. But how many for_each type of macros you see that really try hard > > to achieve that? I believe we shouldn't worry right now about this and rely on > > the fact that root is the given variable. Or do you have an example of what you > > suggested in the other reply, i.e. where it's an evaluation of the heavy call? > > > > > Do you have some idea about > > > how to do that? Something like below? > > > > > > #define for_each_resource_XXX(_root, _p) \ > > > for (typeof(_root) __root = (_root), __p = (_p) = (__root)->child; \ > > > __p && (_p); (_p) = next_resource_XXX(__root, _p)) > > > > This is a bit ugly :-( I would avoid ugliness as long as we have no problem to > > solve (see above). > > Using a local defined variable to avoid double evaluation is standard > practice. I do not understand "avoid ugliness as long as we have no problem to > solve", the problem to solve will be if someone accidentally does > something like "for_each_resource_descendant(root++, res)". *That* will > be a problem when someone finally realizes that the macro is hiding a > double evaluation. Can you explain, why do we need __p and how can we get rid of that? I understand the part of the local variable for root. > So no, this proposal is not "ugly", it is a best practice. See the > definition of min_not_zero() for example. I know that there are a lot of macros that look uglier that this one. -- With Best Regards, Andy Shevchenko