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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46E55C001DE for ; Fri, 21 Jul 2023 21:01:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230478AbjGUVBl (ORCPT ); Fri, 21 Jul 2023 17:01:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229675AbjGUVBi (ORCPT ); Fri, 21 Jul 2023 17:01:38 -0400 Received: from mail-io1-f46.google.com (mail-io1-f46.google.com [209.85.166.46]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 151F51FD2 for ; Fri, 21 Jul 2023 14:01:37 -0700 (PDT) Received: by mail-io1-f46.google.com with SMTP id ca18e2360f4ac-78360b822abso108624239f.2 for ; Fri, 21 Jul 2023 14:01:37 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689973296; x=1690578096; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=yM+Mlo3/qdURDyU/jOXBjf2mTfeeu/j5kwoCIZNPzV4=; b=dCqFe+KZ43t5O8R5VvbWSkGkxR3UQCSAa30uucUJ/GvfoMOanFdIUiKO74oZCPv3+k w1k/spW4U8V2OoUFguPXBOEp2JYySsJYJAcUjO0huXdoTUgya3jGS6yD7U7UaZzVMaPS JH3KsJdBrVwnDeYhD7ezECgPR+h2HEdtfbwSl8RF4Gc+IEvjqvrWjnbC5B+pSqqVDcL1 +3vJluBfmtSO/5vtllpoq3aBgmILuujzYmE7uoaiuynL3aR7IqELWWhV8D/Cx8ofjWi9 yWh0CbxhtFfrh3QGyOCd+9lYb+FUwUL0DFG3PqT5te4l7AkES2IL1msmH8WM+6xY31fE kleQ== X-Gm-Message-State: ABy/qLZci39Z+svv7NU1q/9w0uggEnpJbPRi+U2LMqGFKAiQXHyUbOt3 YVuxQJ8Kn8QdF65PhgfrCiw= X-Google-Smtp-Source: APBJJlEkNbiIvlo9GdVjs7O3HS7p2Fincaq3SVX/f/JJcykDQH0nGgIFUG1fZgJmhjt9Ga2CfRUS3g== X-Received: by 2002:a05:6602:151:b0:787:5ca:d4f with SMTP id v17-20020a056602015100b0078705ca0d4fmr913746iot.8.1689973296198; Fri, 21 Jul 2023 14:01:36 -0700 (PDT) Received: from snowbird ([2601:282:1800:1f50::d356]) by smtp.gmail.com with ESMTPSA id c11-20020a6bfd0b000000b0076ffebfc9fasm1297464ioi.47.2023.07.21.14.01.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Jul 2023 14:01:35 -0700 (PDT) Date: Fri, 21 Jul 2023 14:01:34 -0700 From: Dennis Zhou To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, tj@kernel.org, cl@linux.com, mawupeng1@huawei.com Subject: Re: [PATCH 2/3] mm/percpu.c: optimize the code in pcpu_setup_first_chunk() a little bit Message-ID: References: <20230721131800.20003-1-bhe@redhat.com> <20230721131800.20003-3-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230721131800.20003-3-bhe@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Fri, Jul 21, 2023 at 09:17:59PM +0800, Baoquan He wrote: > This removes the need of local varibale 'chunk', and optimize the code > calling pcpu_alloc_first_chunk() to initialize reserved chunk and > dynamic chunk to make it simpler. > > Signed-off-by: Baoquan He > --- > mm/percpu.c | 32 +++++++++++++------------------- > 1 file changed, 13 insertions(+), 19 deletions(-) > > diff --git a/mm/percpu.c b/mm/percpu.c > index 1480bf283d11..c25b058a46ad 100644 > --- a/mm/percpu.c > +++ b/mm/percpu.c > @@ -2581,7 +2581,6 @@ void __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, > { > size_t size_sum = ai->static_size + ai->reserved_size + ai->dyn_size; > size_t static_size, dyn_size; > - struct pcpu_chunk *chunk; > unsigned long *group_offsets; > size_t *group_sizes; > unsigned long *unit_off; > @@ -2697,7 +2696,7 @@ void __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, > pcpu_unit_pages = ai->unit_size >> PAGE_SHIFT; > pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT; > pcpu_atom_size = ai->atom_size; > - pcpu_chunk_struct_size = struct_size(chunk, populated, > + pcpu_chunk_struct_size = struct_size((struct pcpu_chunk *)0, populated, > BITS_TO_LONGS(pcpu_unit_pages)); > > pcpu_stats_save_ai(ai); > @@ -2735,28 +2734,23 @@ void __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, > > /* > * Initialize first chunk. > - * If the reserved_size is non-zero, this initializes the reserved > - * chunk. If the reserved_size is zero, the reserved chunk is NULL > - * and the dynamic region is initialized here. The first chunk, > - * pcpu_first_chunk, will always point to the chunk that serves > - * the dynamic region. > + * If the reserved_size is non-zero, initializes the reserved chunk ^initialize > + * firstly. If the reserved_size is zero, the reserved chunk is NULL ^ can remove firstly. > + * and the dynamic region is initialized directly. The first chunk, > + * pcpu_first_chunk, will always point to the chunk that serves the > + * dynamic region. Reading this, I'll probably reword this comment to explain the reserved chunk better. > */ > tmp_addr = (unsigned long)base_addr + static_size; > - map_size = ai->reserved_size ?: dyn_size; > - chunk = pcpu_alloc_first_chunk(tmp_addr, map_size); > - > - /* init dynamic chunk if necessary */ > if (ai->reserved_size) { > - pcpu_reserved_chunk = chunk; > - > - tmp_addr = (unsigned long)base_addr + static_size + > - ai->reserved_size; > - map_size = dyn_size; > - chunk = pcpu_alloc_first_chunk(tmp_addr, map_size); > + map_size = ai->reserved_size; > + pcpu_reserved_chunk = pcpu_alloc_first_chunk(tmp_addr, map_size); > } > > - /* link the first chunk in */ > - pcpu_first_chunk = chunk; > + /* init dynamic chunk if necessary */ > + tmp_addr += (unsigned long)ai->reserved_size; I'm not a big fan of += the tmp_addr as I personally find it easier to read if it's just laid out explicitly. > + map_size = dyn_size; > + pcpu_first_chunk = pcpu_alloc_first_chunk(tmp_addr, map_size); > + > pcpu_nr_empty_pop_pages = pcpu_first_chunk->nr_empty_pop_pages; > pcpu_chunk_relocate(pcpu_first_chunk, -1); > > -- > 2.34.1 > Overall, I think this is good, but I'd go 1 step further and get rid of map_size. Regarding tmp_addr, I'd prefer if we kept all the math together. Thanks, Dennis