From nobody Wed Apr 8 08:14:37 2026 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 DDB95C38A2D for ; Mon, 24 Oct 2022 08:16:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229692AbiJXIQv (ORCPT ); Mon, 24 Oct 2022 04:16:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49116 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230286AbiJXIQC (ORCPT ); Mon, 24 Oct 2022 04:16:02 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 48A3C4D800 for ; Mon, 24 Oct 2022 01:15:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666599305; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=L+dfYrksNn4TdevHXr7sUSqhlmuSgsZD4nCKZ/IkdDk=; b=cAUvlvdr7ErAxFrnDg3jWxpv9aR9iP+rNipsO3fUy4JQ2pDQxhIEOeTtuK8mqy7ovZWVio prdJHB2NMjLhc7Y4IlKA/DzvkA1AHxUix9LM8a5y8OXBlSmZlHXuVhcaodYYY7SqcLLMuC zzzZRENNCUDRpZ4UiC23EeKBpafZhDU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-458-6Bt9hgApOOS0VLkaDLvcJA-1; Mon, 24 Oct 2022 04:14:59 -0400 X-MC-Unique: 6Bt9hgApOOS0VLkaDLvcJA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id ED68C185A78F; Mon, 24 Oct 2022 08:14:58 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (ovpn-12-35.pek2.redhat.com [10.72.12.35]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5C16240C6FA0; Mon, 24 Oct 2022 08:14:54 +0000 (UTC) From: Baoquan He To: linux-kernel@vger.kernel.org Cc: Dennis Zhou , Tejun Heo , Christoph Lameter , Andrew Morton , linux-mm@kvack.org, Baoquan He Subject: [PATCH 4/8] mm/percpu: add comment to state the empty populated pages accounting Date: Mon, 24 Oct 2022 16:14:31 +0800 Message-Id: <20221024081435.204970-5-bhe@redhat.com> In-Reply-To: <20221024081435.204970-1-bhe@redhat.com> References: <20221024081435.204970-1-bhe@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When allocating an area from a chunk, pcpu_block_update_hint_alloc() is called to update chunk metadata, including chunk's and global nr_empty_pop_pages. However, if the allocation is not atomic, some blocks may not be populated with pages yet, while we still account it here. The number of pages will be subtracted with pcpu_chunk_populated() when populating pages. Adding code comment to make that more understandable. Signed-off-by: Baoquan He Acked-by: Dennis Zhou --- mm/percpu.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/mm/percpu.c b/mm/percpu.c index a8121302a79c..09e407338573 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -831,13 +831,15 @@ static void pcpu_block_update_hint_alloc(struct pcpu_= chunk *chunk, int bit_off, =20 /* * Update s_block. - * block->first_free must be updated if the allocation takes its place. - * If the allocation breaks the contig_hint, a scan is required to - * restore this hint. */ if (s_block->contig_hint =3D=3D PCPU_BITMAP_BLOCK_BITS) nr_empty_pages++; =20 + /* + * block->first_free must be updated if the allocation takes its place. + * If the allocation breaks the contig_hint, a scan is required to + * restore this hint. + */ if (s_off =3D=3D s_block->first_free) s_block->first_free =3D find_next_zero_bit( pcpu_index_alloc_map(chunk, s_index), @@ -912,6 +914,12 @@ static void pcpu_block_update_hint_alloc(struct pcpu_c= hunk *chunk, int bit_off, } } =20 + /* + * If the allocation is not atomic, some blocks may not + * be populated with pages, while we account it here. + * The number of pages will be subtracted with + * pcpu_chunk_populated() when populating pages. + */ if (nr_empty_pages) pcpu_update_empty_pages(chunk, -nr_empty_pages); =20 --=20 2.34.1