From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f43.google.com (mail-oa1-f43.google.com [209.85.160.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5AF043EE1F3 for ; Fri, 20 Mar 2026 19:27:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.43 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774034876; cv=none; b=rOg61AZvcjL3xYtULkyDcs86J3fluoFRWNIBrFyYJ5DO9zIxA62fnfcoGf8M7gufvHTcv/MO6Bg817O9SEatNzvQrVgqV1bmh4k2x4s1YjQWqpQkGU4FvrSH/u/PCexylEKGiHREuvQIMGp4MOySkdcyijLX9EtHsp8G1yRqZy0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774034876; c=relaxed/simple; bh=1dUCBz1ekRwGyhp7aar8Ynyko8f4W8fyU8IBjgTWVT0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dxtLNvHcutKyeTPxImfQOBrayb4jgztS05YN/ywEb4vxZCxM/5s3Q4vsRxc/2GwWCOsLRBFL1Q165jC7kUXB/cROe/ZjA0HuUL6BokGCGF1/h9UuTBFGTanEcjGcDnlurSYgDL0sCXtX8Feu+63tRxCtfDEhr5b2nX+gol8JbeU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=QrLXInbl; arc=none smtp.client-ip=209.85.160.43 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="QrLXInbl" Received: by mail-oa1-f43.google.com with SMTP id 586e51a60fabf-4043b27ddeaso1557799fac.1 for ; Fri, 20 Mar 2026 12:27:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1774034873; x=1774639673; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=KPp25151sWevMzEffEXxfQEZtCUw8Iu/6c7CfKgDuL4=; b=QrLXInblHomAh6OHIjBFUyK8E28FJX5P1/b3FnAs6J102tRryk9SuMvI8F4JBa9t1T 1GvBGBe79kkmx9aruajSh5c8OMADIlD19sf+UDc67eTIcgwl+LyjJiK3QUs8z48oTLwm T0G0kgFKVDgeaIxt2QBBRhPDOsxnxdXRspMJf3zYWJX+8UXjgXxWnjxr8c5KKqx9gS6N 8aisPKhV8GyNd9qRvp2BwiOeDd8PEvxNmluNFJn+whebSFBZt/vOr+s41pxe7xzPJglY EhtPFPJwIYHjEQ+XCzImYs8xiBRd4ubLWwBmNUynKo16gudcOCtT15vG65ZLpkVwSMjk tj9Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774034873; x=1774639673; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=KPp25151sWevMzEffEXxfQEZtCUw8Iu/6c7CfKgDuL4=; b=SLeJLUgHXrhlj68PbTFEps3+41nccKyoq2UwAemRlGLEqjTdIiFRIP08pAkud3Lkl2 VxRqr54HFyU/R3mWwiPw6G6/Aki8hZJSyAnNCIZWJ1ThbLtion+WYumndb8ZWe0eYLqW mAvbA7Mm31RbGQ/HywX93A/sG9Pit0wivCsQd8Z7nAXFL1JItKcJ7rovFYEynJcAtej/ xMUEbCTDMJd6EMG+IQTE6KW7sm2MJCK2njj2wy7Xy/HIjx1nA1RHn0aB4ez06/hpsqLK hirESe7kyH/SmrqU3f2TL6LS/PiEHJALop9GXKN6ZG7+ngMQQjiuGxGQoYRuELlMlout BFCg== X-Forwarded-Encrypted: i=1; AJvYcCX5Qrq+SMaehuhcRe768euJHEdXOWq4ZrTOUUbCcMjGHWSssFPpZoHRp+ZQZm8LIQEIS2vyJsOs@vger.kernel.org X-Gm-Message-State: AOJu0YzVgzbYlSZObKzRbtNjFL4e4SwQLcpBZrQNaCOgMH2mdvkv0R+i fbUOIVme76zdlec0pjgsRadft8Gk4IQA7io6PMUygBMS//fRipH4q4sa X-Gm-Gg: ATEYQzy6aKC1IYLmnSYHwxQvk2f/+onatsSKMIOA/f9XFPUh8BZMEy3X2e3VRq9qxmk 9eDa0v4usHxLy1UpDAjKRJum5NLgVoKwKYqe/g3cWyHije7IgmIeU1pa+U9ufZV1RwAoNLF6JvG XMl5bEQjhub/OdoGdxmsz5v2EbjC6lxlLUWdgtXZqTlUXDc9AwugMR8HoZhdqs22QkBzIsSYuSr Kr7FtjJmnleSCEqGFzrbaosAmBwNd9dv46YiYXE5lxWiROnY/x7HLDDNx/1e0yRajJDSH7iz/GR 34GiQ8fZNKe4F2wawmECeVfbtdP9BdsggmFl4TkTQIj4tuxCt/maiKsSH4LsWes8XWhBl7gLety kXfPXWmucpmjNRh/QXMfCdzh3sZYdnlf2yKS15/fw0jflTdqwK5QvA8EPlvAzazQFJWM761QPGa CAguoQYKKQYWcNR3eSEvxDdAqkANh851gwWlRGdD7GoNeUYw== X-Received: by 2002:a05:6870:f150:b0:409:7a01:6e2f with SMTP id 586e51a60fabf-41c10ffd393mr2670572fac.11.1774034872998; Fri, 20 Mar 2026 12:27:52 -0700 (PDT) Received: from localhost ([2a03:2880:10ff:56::]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-41c14d73a19sm2659524fac.11.2026.03.20.12.27.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Mar 2026 12:27:52 -0700 (PDT) From: Nhat Pham To: kasong@tencent.com Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org, apopple@nvidia.com, axelrasmussen@google.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, bhe@redhat.com, byungchul@sk.com, cgroups@vger.kernel.org, chengming.zhou@linux.dev, chrisl@kernel.org, corbet@lwn.net, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jannh@google.com, joshua.hahnjy@gmail.com, lance.yang@linux.dev, lenb@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, lorenzo.stoakes@oracle.com, matthew.brost@intel.com, mhocko@suse.com, muchun.song@linux.dev, npache@redhat.com, nphamcs@gmail.com, pavel@kernel.org, peterx@redhat.com, peterz@infradead.org, pfalcato@suse.de, rafael@kernel.org, rakie.kim@sk.com, roman.gushchin@linux.dev, rppt@kernel.org, ryan.roberts@arm.com, shakeel.butt@linux.dev, shikemeng@huaweicloud.com, surenb@google.com, tglx@kernel.org, vbabka@suse.cz, weixugc@google.com, ying.huang@linux.alibaba.com, yosry.ahmed@linux.dev, yuanchu@google.com, zhengqi.arch@bytedance.com, ziy@nvidia.com, kernel-team@meta.com, riel@surriel.com Subject: [PATCH v5 11/21] zswap: move zswap entry management to the virtual swap descriptor Date: Fri, 20 Mar 2026 12:27:25 -0700 Message-ID: <20260320192735.748051-12-nphamcs@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260320192735.748051-1-nphamcs@gmail.com> References: <20260320192735.748051-1-nphamcs@gmail.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Remove the zswap tree and manage zswap entries directly through the virtual swap descriptor. This re-partitions the zswap pool (by virtual swap cluster), which eliminates zswap tree lock contention. Signed-off-by: Nhat Pham --- include/linux/zswap.h | 6 +++ mm/vswap.c | 100 ++++++++++++++++++++++++++++++++++++++++++ mm/zswap.c | 40 ----------------- 3 files changed, 106 insertions(+), 40 deletions(-) diff --git a/include/linux/zswap.h b/include/linux/zswap.h index 1a04caf283dc8..7eb3ce7e124fc 100644 --- a/include/linux/zswap.h +++ b/include/linux/zswap.h @@ -6,6 +6,7 @@ #include struct lruvec; +struct zswap_entry; extern atomic_long_t zswap_stored_pages; @@ -33,6 +34,11 @@ void zswap_lruvec_state_init(struct lruvec *lruvec); void zswap_folio_swapin(struct folio *folio); bool zswap_is_enabled(void); bool zswap_never_enabled(void); +void *zswap_entry_store(swp_entry_t swpentry, struct zswap_entry *entry); +void *zswap_entry_load(swp_entry_t swpentry); +void *zswap_entry_erase(swp_entry_t swpentry); +bool zswap_empty(swp_entry_t swpentry); + #else struct zswap_lruvec_state {}; diff --git a/mm/vswap.c b/mm/vswap.c index 3027294cd872b..9b2122647b850 100644 --- a/mm/vswap.c +++ b/mm/vswap.c @@ -10,6 +10,7 @@ #include #include #include +#include #include "swap.h" #include "swap_table.h" @@ -37,11 +38,13 @@ * Swap descriptor - metadata of a swapped out page. * * @slot: The handle to the physical swap slot backing this page. + * @zswap_entry: The zswap entry associated with this swap slot. * @swap_cache: The folio in swap cache. * @shadow: The shadow entry. */ struct swp_desc { swp_slot_t slot; + struct zswap_entry *zswap_entry; union { struct folio *swap_cache; void *shadow; @@ -238,6 +241,7 @@ static void __vswap_alloc_from_cluster(struct vswap_cluster *cluster, int start) for (i = 0; i < nr; i++) { desc = &cluster->descriptors[start + i]; desc->slot.val = 0; + desc->zswap_entry = NULL; } cluster->count += nr; } @@ -1008,6 +1012,102 @@ void __swap_cache_replace_folio(struct folio *old, struct folio *new) rcu_read_unlock(); } +#ifdef CONFIG_ZSWAP +/** + * zswap_entry_store - store a zswap entry for a swap entry + * @swpentry: the swap entry + * @entry: the zswap entry to store + * + * Stores a zswap entry in the swap descriptor for the given swap entry. + * The cluster is locked during the store operation. + * + * Return: the old zswap entry if one existed, NULL otherwise + */ +void *zswap_entry_store(swp_entry_t swpentry, struct zswap_entry *entry) +{ + struct vswap_cluster *cluster = NULL; + struct swp_desc *desc; + void *old; + + rcu_read_lock(); + desc = vswap_iter(&cluster, swpentry.val); + if (!desc) { + rcu_read_unlock(); + return NULL; + } + + old = desc->zswap_entry; + desc->zswap_entry = entry; + spin_unlock(&cluster->lock); + rcu_read_unlock(); + + return old; +} + +/** + * zswap_entry_load - load a zswap entry for a swap entry + * @swpentry: the swap entry + * + * Loads the zswap entry from the swap descriptor for the given swap entry. + * + * Return: the zswap entry if one exists, NULL otherwise + */ +void *zswap_entry_load(swp_entry_t swpentry) +{ + struct vswap_cluster *cluster = NULL; + struct swp_desc *desc; + void *zswap_entry; + + rcu_read_lock(); + desc = vswap_iter(&cluster, swpentry.val); + if (!desc) { + rcu_read_unlock(); + return NULL; + } + + zswap_entry = desc->zswap_entry; + spin_unlock(&cluster->lock); + rcu_read_unlock(); + + return zswap_entry; +} + +/** + * zswap_entry_erase - erase a zswap entry for a swap entry + * @swpentry: the swap entry + * + * Erases the zswap entry from the swap descriptor for the given swap entry. + * The cluster is locked during the erase operation. + * + * Return: the zswap entry that was erased, NULL if none existed + */ +void *zswap_entry_erase(swp_entry_t swpentry) +{ + struct vswap_cluster *cluster = NULL; + struct swp_desc *desc; + void *old; + + rcu_read_lock(); + desc = vswap_iter(&cluster, swpentry.val); + if (!desc) { + rcu_read_unlock(); + return NULL; + } + + old = desc->zswap_entry; + desc->zswap_entry = NULL; + spin_unlock(&cluster->lock); + rcu_read_unlock(); + + return old; +} + +bool zswap_empty(swp_entry_t swpentry) +{ + return xa_empty(&vswap_cluster_map); +} +#endif /* CONFIG_ZSWAP */ + int vswap_init(void) { int i; diff --git a/mm/zswap.c b/mm/zswap.c index f7313261673ff..72441131f094e 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -223,37 +223,6 @@ static bool zswap_has_pool; * helpers and fwd declarations **********************************/ -static DEFINE_XARRAY(zswap_tree); - -#define zswap_tree_index(entry) (entry.val) - -static inline void *zswap_entry_store(swp_entry_t swpentry, - struct zswap_entry *entry) -{ - pgoff_t offset = zswap_tree_index(swpentry); - - return xa_store(&zswap_tree, offset, entry, GFP_KERNEL); -} - -static inline void *zswap_entry_load(swp_entry_t swpentry) -{ - pgoff_t offset = zswap_tree_index(swpentry); - - return xa_load(&zswap_tree, offset); -} - -static inline void *zswap_entry_erase(swp_entry_t swpentry) -{ - pgoff_t offset = zswap_tree_index(swpentry); - - return xa_erase(&zswap_tree, offset); -} - -static inline bool zswap_empty(swp_entry_t swpentry) -{ - return xa_empty(&zswap_tree); -} - #define zswap_pool_debug(msg, p) \ pr_debug("%s pool %s\n", msg, (p)->tfm_name) @@ -1445,13 +1414,6 @@ static bool zswap_store_page(struct page *page, goto compress_failed; old = zswap_entry_store(page_swpentry, entry); - if (xa_is_err(old)) { - int err = xa_err(old); - - WARN_ONCE(err != -ENOMEM, "unexpected xarray error: %d\n", err); - zswap_reject_alloc_fail++; - goto store_failed; - } /* * We may have had an existing entry that became stale when @@ -1498,8 +1460,6 @@ static bool zswap_store_page(struct page *page, return true; -store_failed: - zs_free(pool->zs_pool, entry->handle); compress_failed: zswap_entry_cache_free(entry); return false; -- 2.52.0