From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EBC21C43441 for ; Mon, 12 Nov 2018 15:12:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B1BA4223D0 for ; Mon, 12 Nov 2018 15:12:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B1BA4223D0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729756AbeKMBGH (ORCPT ); Mon, 12 Nov 2018 20:06:07 -0500 Received: from mga12.intel.com ([192.55.52.136]:21937 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726443AbeKMBGH (ORCPT ); Mon, 12 Nov 2018 20:06:07 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Nov 2018 07:12:15 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,495,1534834800"; d="scan'208";a="88679704" Received: from ahduyck-mobl.amr.corp.intel.com (HELO [10.251.10.23]) ([10.251.10.23]) by orsmga007.jf.intel.com with ESMTP; 12 Nov 2018 07:12:14 -0800 Subject: Re: [mm PATCH v5 7/7] mm: Use common iterator for deferred_init_pages and deferred_free_pages To: Pavel Tatashin Cc: akpm@linux-foundation.org, linux-mm@kvack.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, davem@davemloft.net, pavel.tatashin@microsoft.com, mhocko@suse.com, mingo@kernel.org, kirill.shutemov@linux.intel.com, dan.j.williams@intel.com, dave.jiang@intel.com, rppt@linux.vnet.ibm.com, willy@infradead.org, vbabka@suse.cz, khalid.aziz@oracle.com, ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net, yi.z.zhang@linux.intel.com References: <154145268025.30046.11742652345962594283.stgit@ahduyck-desk1.jf.intel.com> <154145280115.30046.13334106887516645119.stgit@ahduyck-desk1.jf.intel.com> <20181110041338.7ttram7po7a2ssz7@xakep.localdomain> From: Alexander Duyck Message-ID: Date: Mon, 12 Nov 2018 07:12:13 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181110041338.7ttram7po7a2ssz7@xakep.localdomain> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/9/2018 8:13 PM, Pavel Tatashin wrote: > On 18-11-05 13:20:01, Alexander Duyck wrote: >> +static unsigned long __next_pfn_valid_range(unsigned long *i, >> + unsigned long end_pfn) >> { >> - if (!pfn_valid_within(pfn)) >> - return false; >> - if (!(pfn & (pageblock_nr_pages - 1)) && !pfn_valid(pfn)) >> - return false; >> - return true; >> + unsigned long pfn = *i; >> + unsigned long count; >> + >> + while (pfn < end_pfn) { >> + unsigned long t = ALIGN(pfn + 1, pageblock_nr_pages); >> + unsigned long pageblock_pfn = min(t, end_pfn); >> + >> +#ifndef CONFIG_HOLES_IN_ZONE >> + count = pageblock_pfn - pfn; >> + pfn = pageblock_pfn; >> + if (!pfn_valid(pfn)) >> + continue; >> +#else >> + for (count = 0; pfn < pageblock_pfn; pfn++) { >> + if (pfn_valid_within(pfn)) { >> + count++; >> + continue; >> + } >> + >> + if (count) >> + break; >> + } >> + >> + if (!count) >> + continue; >> +#endif >> + *i = pfn; >> + return count; >> + } >> + >> + return 0; >> } >> >> +#define for_each_deferred_pfn_valid_range(i, start_pfn, end_pfn, pfn, count) \ >> + for (i = (start_pfn), \ >> + count = __next_pfn_valid_range(&i, (end_pfn)); \ >> + count && ({ pfn = i - count; 1; }); \ >> + count = __next_pfn_valid_range(&i, (end_pfn))) > > Can this be improved somehow? It took me a while to understand this > piece of code. i is actually end of block, and not an index by PFN, ({pfn = i - count; 1;}) is > simply hard to parse. Why can't we make __next_pfn_valid_range() to > return both end and a start of a block? One thing I could do is flip the direction and work from the end to the start. If I did that then 'i' and 'pfn' would be the same value and I wouldn't have to do the subtraction. If that works for you I could probably do that and it may actually be more efficient. Otherwise I could probably pass pfn as a reference, and compute it in the case where count is non-zero. > The rest is good: > > Reviewed-by: Pavel Tatashin > > Thank you, > Pasha >