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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 555ABCA0FF9 for ; Sat, 30 Aug 2025 04:23:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 800906B002C; Sat, 30 Aug 2025 00:23:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7B1206B002F; Sat, 30 Aug 2025 00:23:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6EE046B0031; Sat, 30 Aug 2025 00:23:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 5D51F6B002C for ; Sat, 30 Aug 2025 00:23:38 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 03964140A2E for ; Sat, 30 Aug 2025 04:23:37 +0000 (UTC) X-FDA: 83832130116.26.3BEE89F Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf30.hostedemail.com (Postfix) with ESMTP id 2B08E8000B for ; Sat, 30 Aug 2025 04:23:35 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=PAuPgW6D; spf=pass (imf30.hostedemail.com: domain of chrisl@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=chrisl@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1756527816; h=from:from:sender: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:dkim-signature; bh=bfIAEbnEfPA8NLHbFihkx4jLwJRo+ySAEqJMEysZ3nE=; b=ORKUJxp6F79a7TrfLbw47Ut9buAaFJ950mXsruIeSxsWk9/sTolpCO4eZJWSSxb7GtT6pC Q+mLHVKtxRJuponEMjWVZLsfEhQ/ayDx26B1C+nxmDZ0XYhUKNJDTL6LJs7lwW/ZppbF+/ Q2brsX06pD0pVUn5Byd8VtXMhCWH6/E= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=PAuPgW6D; spf=pass (imf30.hostedemail.com: domain of chrisl@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=chrisl@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1756527816; a=rsa-sha256; cv=none; b=NIbGdY2RTIklqDUWV6QCD5qZlZ/Nk0ZwL9ZEFrtr/5PrwdvR5nIZN+dLId+hAtQ2Qb9cRW emn3oazhtLAJ+Ue16eDnZwh08bMy3bL/Gw8Yhi2Z9ZYfMhwC7GJNFYByEf9YkNebF182dX hxzZjcZdaKeLzo16G5yF/mpRJFVu1IA= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 1852B44517 for ; Sat, 30 Aug 2025 04:23:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3FC5C4CEF8 for ; Sat, 30 Aug 2025 04:23:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756527814; bh=D9KYpDUP5BVnW8FywXZwKnRRF1ITjfxzDIQ9H8sxo4Q=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=PAuPgW6DTcFnirnw9UcqldJvkgib7KlFB/JhUA3yke1jVHWwKEou+iqZedEtWCd9f tkGu1jrZxyuHCq56vlsy2IwPWxY8PL5832VV3EaVn8azpr2q5SI1jbKS1yWC+zZWQQ allQPhuRUoHiDg1wV5RcCmDknW8AJHFEkq7ZQqOTMVVSDXfIXsMoaNLHLMeioUlxbI HJ7lyW8uQ79M0MEosGWBzqqsE7wLSE++eqa4tcYess/I/lvAtHhWcLfD30c/MeMuCW ZpQeUmMGZXz24pA4Gc3rxzpSiCYP4s6xaZSJuNW0NhHU3PkxOyPRcyHx1JV1tct38z 78x0KotLZGQsA== Received: by mail-yb1-f179.google.com with SMTP id 3f1490d57ef6-e970a7f0e54so2343301276.2 for ; Fri, 29 Aug 2025 21:23:34 -0700 (PDT) X-Gm-Message-State: AOJu0Yz94V2u2qYIzb5y9W51MMoS8vi2+OCo5RsrL4K9IN90HJNqWyzc zL8AxHb9PRj3XhdyB2/bCO3g++Q8JlHfEiccv26cpYTLbkgmsNNGRwmNkZ3Iucu7UZpbFyvaaif dXo6G5V9w+9JAgJa61/jxe+20mlacvGOmRb+OD1RHWg== X-Google-Smtp-Source: AGHT+IHUYw5iTZZitWn5/kKGBPhEdinJ2+s/C+umqFngBTgvc3KVlGfasTHujxDCl4c1wk8GQEV+wkrPMOG9LwOTEh4= X-Received: by 2002:a05:690c:a053:b0:722:7941:4f63 with SMTP id 00721157ae682-722794152b5mr2931557b3.38.1756527814094; Fri, 29 Aug 2025 21:23:34 -0700 (PDT) MIME-Version: 1.0 References: <20250822192023.13477-1-ryncsn@gmail.com> <20250822192023.13477-10-ryncsn@gmail.com> In-Reply-To: <20250822192023.13477-10-ryncsn@gmail.com> From: Chris Li Date: Fri, 29 Aug 2025 21:23:23 -0700 X-Gmail-Original-Message-ID: X-Gm-Features: Ac12FXz6jrOEFnuqwA82LzX_2OD8nZLAfwzRWUeO3BPVny99yHfT1S7Pw2lZEkg Message-ID: Subject: Re: [PATCH 9/9] mm, swap: use a single page for swap table when the size fits To: Kairui Song Cc: linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Hugh Dickins , Barry Song , Baoquan He , Nhat Pham , Kemeng Shi , Baolin Wang , Ying Huang , Johannes Weiner , David Hildenbrand , Yosry Ahmed , Lorenzo Stoakes , Zi Yan , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 2B08E8000B X-Stat-Signature: kjr5bsxhzyhexzfhy4t8cit7e47eeggh X-Rspam-User: X-HE-Tag: 1756527815-306485 X-HE-Meta: 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 25w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Acked-by: Chris Li Chris On Fri, Aug 22, 2025 at 12:21=E2=80=AFPM Kairui Song wro= te: > > From: Kairui Song > > We have a cluster size of 512 slots. Each slot consumes 8 bytes in swap > table so the swap table size of each cluster is exactly one page (4K). > > If that condition is true, allocate one page direct and disable the slab > cache to reduce the memory usage of swap table and avoid fragmentation. > > Co-developed-by: Chris Li > Signed-off-by: Chris Li > Signed-off-by: Kairui Song > --- > mm/swap_table.h | 2 ++ > mm/swapfile.c | 50 ++++++++++++++++++++++++++++++++++++++++--------- > 2 files changed, 43 insertions(+), 9 deletions(-) > > diff --git a/mm/swap_table.h b/mm/swap_table.h > index 4e97513b11ef..984474e37dd7 100644 > --- a/mm/swap_table.h > +++ b/mm/swap_table.h > @@ -11,6 +11,8 @@ struct swap_table { > atomic_long_t entries[SWAPFILE_CLUSTER]; > }; > > +#define SWP_TABLE_USE_PAGE (sizeof(struct swap_table) =3D=3D PAGE_SIZE) > + > /* > * A swap table entry represents the status of a swap slot on a swap > * (physical or virtual) device. The swap table in each cluster is a > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 00651e947eb2..7539ee26d59a 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -432,6 +432,38 @@ static inline unsigned int cluster_offset(struct swa= p_info_struct *si, > return cluster_index(si, ci) * SWAPFILE_CLUSTER; > } > > +static struct swap_table *swap_table_alloc(gfp_t gfp) > +{ > + struct folio *folio; > + > + if (!SWP_TABLE_USE_PAGE) > + return kmem_cache_zalloc(swap_table_cachep, gfp); > + > + folio =3D folio_alloc(gfp | __GFP_ZERO, 0); > + if (folio) > + return folio_address(folio); > + return NULL; > +} > + > +static void swap_table_free_folio_rcu_cb(struct rcu_head *head) > +{ > + struct folio *folio; > + > + folio =3D page_folio(container_of(head, struct page, rcu_head)); > + folio_put(folio); > +} > + > +static void swap_table_free(struct swap_table *table) > +{ > + if (!SWP_TABLE_USE_PAGE) { > + kmem_cache_free(swap_table_cachep, table); > + return; > + } > + > + call_rcu(&(folio_page(virt_to_folio(table), 0)->rcu_head), > + swap_table_free_folio_rcu_cb); > +} > + > static void swap_cluster_free_table(struct swap_cluster_info *ci) > { > unsigned int ci_off; > @@ -445,7 +477,7 @@ static void swap_cluster_free_table(struct swap_clust= er_info *ci) > table =3D (void *)rcu_dereference_protected(ci->table, true); > rcu_assign_pointer(ci->table, NULL); > > - kmem_cache_free(swap_table_cachep, table); > + swap_table_free(table); > } > > /* > @@ -469,8 +501,7 @@ swap_cluster_alloc_table(struct swap_info_struct *si, > lockdep_assert_held(&ci->lock); > lockdep_assert_held(&this_cpu_ptr(&percpu_swap_cluster)->lock); > > - table =3D kmem_cache_zalloc(swap_table_cachep, > - __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_N= OWARN); > + table =3D swap_table_alloc(__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_= NOWARN); > if (table) { > rcu_assign_pointer(ci->table, table); > return ci; > @@ -485,7 +516,7 @@ swap_cluster_alloc_table(struct swap_info_struct *si, > if (!(si->flags & SWP_SOLIDSTATE)) > spin_unlock(&si->global_cluster_lock); > local_unlock(&percpu_swap_cluster.lock); > - table =3D kmem_cache_zalloc(swap_table_cachep, __GFP_HIGH | GFP_K= ERNEL); > + table =3D swap_table_alloc(__GFP_HIGH | GFP_KERNEL); > > local_lock(&percpu_swap_cluster.lock); > if (!(si->flags & SWP_SOLIDSTATE)) > @@ -522,7 +553,7 @@ swap_cluster_alloc_table(struct swap_info_struct *si, > > free_table: > if (table) > - kmem_cache_free(swap_table_cachep, table); > + swap_table_free(table); > return ci; > } > > @@ -740,7 +771,7 @@ static int inc_cluster_info_page(struct swap_info_str= uct *si, > > ci =3D cluster_info + idx; > if (!ci->table) { > - table =3D kmem_cache_zalloc(swap_table_cachep, GFP_KERNEL= ); > + table =3D swap_table_alloc(GFP_KERNEL); > if (!table) > return -ENOMEM; > rcu_assign_pointer(ci->table, table); > @@ -4076,9 +4107,10 @@ static int __init swapfile_init(void) > * only, and all swap cache readers (swap_cache_*) verifies > * the content before use. So it's safe to use RCU slab here. > */ > - swap_table_cachep =3D kmem_cache_create("swap_table", > - sizeof(struct swap_table), > - 0, SLAB_PANIC | SLAB_TYPESAFE_BY_RCU, NULL); > + if (!SWP_TABLE_USE_PAGE) > + swap_table_cachep =3D kmem_cache_create("swap_table", > + sizeof(struct swap_table), > + 0, SLAB_PANIC | SLAB_TYPESAFE_BY_RCU,= NULL); > > #ifdef CONFIG_MIGRATION > if (swapfile_maximum_size >=3D (1UL << SWP_MIG_TOTAL_BITS)) > -- > 2.51.0 >