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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5DDB3CDB474 for ; Tue, 17 Oct 2023 00:35:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E6F098D00DD; Mon, 16 Oct 2023 20:35:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E1F298D00B8; Mon, 16 Oct 2023 20:35:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CE7138D00DD; Mon, 16 Oct 2023 20:35:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id BF9A58D00B8 for ; Mon, 16 Oct 2023 20:35:24 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 8D116A0C9D for ; Tue, 17 Oct 2023 00:35:24 +0000 (UTC) X-FDA: 81353084568.04.BE25D2A Received: from mail-pl1-f173.google.com (mail-pl1-f173.google.com [209.85.214.173]) by imf23.hostedemail.com (Postfix) with ESMTP id BCC9D140015 for ; Tue, 17 Oct 2023 00:35:21 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=HzDbGK2b; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf23.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.214.173 as permitted sender) smtp.mailfrom=nphamcs@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1697502921; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=TAwiYt7jZ0jTSch20EJdCPnumHKLIIb6QfY26Jbdiok=; b=L5uJGKnAy8FQw330GM2Z29YVmJpngidDb6nAEsDeJbPUjICpn5CAr+4KlqxuLKbvCc7Y7e vVHS/aT1XWof8jBaKVzs+8nDu5hgCmsbNqtB7pgPt+WkI5o0N1rneM1L7iDBnVOFSKRicz 237acwAyj8aGolbDuSaoFsybO46Q9xA= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=HzDbGK2b; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf23.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.214.173 as permitted sender) smtp.mailfrom=nphamcs@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1697502921; a=rsa-sha256; cv=none; b=0w7P8fdeef/LQ2jDjCoRT2ngiTX4Jf9PalSQFDMfvdQUOOaup8osBtbB0fephjNwj8/u03 HImseOjq5uJNolOeZkOncWpT/Kd6jg+Wn/43USB5KldzLQNlzWXAf3AyOaUiKnsFR/PCzF agUSHS77uHfNFcZfpk8JZMI2VuyN8Vw= Received: by mail-pl1-f173.google.com with SMTP id d9443c01a7336-1c9c5a1b87bso34532835ad.3 for ; Mon, 16 Oct 2023 17:35:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1697502921; x=1698107721; darn=kvack.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=TAwiYt7jZ0jTSch20EJdCPnumHKLIIb6QfY26Jbdiok=; b=HzDbGK2buLf/Vs8nQriwNNifbXGp/J7FITrPGgmqTiq986HDEpTxpT7TuVXzWZnmVF dCOKDzUaKvaQdY3Mpm+NUDyl6TP9I0HJCyax+4pgKbjswvpqTGMfBllJ0XmrnN0uskmj rse8cLtwqht2ZECgIA7OkI+hvU39vCmZWdqEYgaHH58lVPnETctBBezLAg9GuNVzJ9Jc a06oa0YX1wRlZVKIquDAWJzROYx+Sum20i2eFiRJwSGwbunYm5o5WLFQD+rc4RrMzVdJ ZeVEkgQ2xiStXJCUmOKDmVyWFf2X9wYiIt7yMZOlvI6OhfRKeo2f54vY9DhdQ4kUjjbM 4A8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697502921; x=1698107721; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=TAwiYt7jZ0jTSch20EJdCPnumHKLIIb6QfY26Jbdiok=; b=tYgRsq54Enp8l/bkK3zV0tTDRRQBLDDs/unAwzc4KNJm6qLTIXCMLdwzCJ4xWnH+wZ FIfWgSnQBp3tv71dzZFuo9h/u2XW3qMI/UMYjKjAXne9wWgX3xveM+d8Zo6aZPI+igQo +qG7lZFwiyj66VZHsKySVtubxjroB5ne+BdQN/e3RvY2AHmIA7dspq6jVKAAywnjW4ee KRGfwYP8aRvMoTwyRl95o0ANWYhZAZNX8VrZjmfAsL8L+16MF2rxod422/w7aHRYWVfZ vKoI8zUbcnsI73D07WucnMAQHtiW1qPCrINPi+l4HJefKFnCizGn+WhE8Nhuv45uDWL9 +cBA== X-Gm-Message-State: AOJu0YyRUtpEhjs/xwi+Wc/3/ArZdgfpQ1N+UDhE7rSdRvN/LhjI1wwl pF8YQ9ND9HPds2q7LR/7HOs= X-Google-Smtp-Source: AGHT+IHetkovzeS4CXVvYSqkxsOsLDksqAtX486TpH5iBtoG7n3TfpIRVgIp+F/1WP2Fk4nkn72LRQ== X-Received: by 2002:a17:903:23cf:b0:1ca:4ad7:6878 with SMTP id o15-20020a17090323cf00b001ca4ad76878mr763231plh.8.1697502920631; Mon, 16 Oct 2023 17:35:20 -0700 (PDT) Received: from localhost (fwdproxy-prn-119.fbsv.net. [2a03:2880:ff:77::face:b00c]) by smtp.gmail.com with ESMTPSA id u10-20020a17090341ca00b001b7f40a8959sm201875ple.76.2023.10.16.17.35.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Oct 2023 17:35:20 -0700 (PDT) From: Nhat Pham To: akpm@linux-foundation.org Cc: hannes@cmpxchg.org, cerasuolodomenico@gmail.com, yosryahmed@google.com, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com, hughd@google.com, corbet@lwn.net, konrad.wilk@oracle.com, senozhatsky@chromium.org, rppt@kernel.org, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, david@ixit.cz Subject: [PATCH 1/2] swap: allows swap bypassing on zswap store failure Date: Mon, 16 Oct 2023 17:35:18 -0700 Message-Id: <20231017003519.1426574-2-nphamcs@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231017003519.1426574-1-nphamcs@gmail.com> References: <20231017003519.1426574-1-nphamcs@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: BCC9D140015 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 8q974disx1daf1r839wwyzo1puu3pwon X-HE-Tag: 1697502921-724119 X-HE-Meta: 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 A7qwK1qa 5M+XnYo3SZ6yTe+J9Hg4Ebnv2BoW1bOxkUUS6eZljn7KxENIGDKZ6RHiI9lg337iYJprX+dMYuX2+PfKVvJS0c32ABRMzB5+VdK35giy/2l5MHQMm/wz8FlksIupt0VTi6qRvogTeRFXv35zTbqxVhcEqxKnD+0nn2K2VHcLLkPP7PBD3U2Y9b/aGQ0KiBNmkgD16Y5FaxtE7yWDFuPlA0ZHLO8AypqoQCWBR/hsxkJAj2VfuKIZdt8DQAlDo8wqlwd68DVxzju2N8qrW+oaMFZxJgs1+oc5SinptvbLpLV8bvSvkses8txDGru5osB3L6NA5xqiqmoZqY2Gm02NNzwGZBMLXVgtfNMcYV8NOlTI7IzkEE3twNmU4Zbx9RcQDhKJtfuYLXjT6hig11KJG1pQaS79FMFaUUHDUmBdm0nAC7Wu4hC5C+fC8JPhfxbe0kNPSAYOgg+Lqlv6RrTIwMEQCrJzs0R2SKJtTJ2sIIatVdA8= 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: During our experiment with zswap, we sometimes observe swap IOs even though the zswap pool limit is never hit. This is due to occasional zswap store failures, in which case the page will be written straight to the swapping device. This prevents many users who cannot tolerate swapping from adopting zswap to save memory where possible. This patch adds the option to bypass swap when a zswap store fails. The feature is disabled by default (to preserve the existing behavior), and can be enabled via a new zswap module parameter. When enabled, swapping is all but prevented (except for when the zswap pool is full and have to write pages back to swap). Suggested-by: Johannes Weiner Signed-off-by: Nhat Pham --- Documentation/admin-guide/mm/zswap.rst | 9 +++++++++ include/linux/zswap.h | 9 +++++++++ mm/page_io.c | 6 ++++++ mm/shmem.c | 8 ++++++-- mm/zswap.c | 4 ++++ 5 files changed, 34 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/mm/zswap.rst b/Documentation/admin-guide/mm/zswap.rst index ae8597a67804..82fa8148a65a 100644 --- a/Documentation/admin-guide/mm/zswap.rst +++ b/Documentation/admin-guide/mm/zswap.rst @@ -153,6 +153,15 @@ attribute, e. g.:: Setting this parameter to 100 will disable the hysteresis. +Many users cannot tolerate the swapping that comes with zswap store failures, +due to the IO incurred if these pages are needed later on. In this scenario, +users can bypass swapping when zswap store attempts fail (and keep the pages +in memory) as follows: + + echo Y > /sys/module/zswap/parameters/bypass_swap_when_store_fail_enabled + +Note that swapping due to writeback is not disabled with this option. + When there is a sizable amount of cold memory residing in the zswap pool, it can be advantageous to proactively write these cold pages to swap and reclaim the memory for other use cases. By default, the zswap shrinker is disabled. diff --git a/include/linux/zswap.h b/include/linux/zswap.h index 04f80b64a09b..c67da5223894 100644 --- a/include/linux/zswap.h +++ b/include/linux/zswap.h @@ -7,6 +7,7 @@ extern u64 zswap_pool_total_size; extern atomic_t zswap_stored_pages; +extern bool zswap_bypass_swap_when_store_fail_enabled; #ifdef CONFIG_ZSWAP @@ -18,6 +19,10 @@ void zswap_swapoff(int type); bool zswap_remove_swpentry_from_lru(swp_entry_t swpentry); void zswap_insert_swpentry_into_lru(swp_entry_t swpentry); +static inline bool zswap_bypass_swap_when_store_fail(void) +{ + return zswap_bypass_swap_when_store_fail_enabled; +} #else static inline bool zswap_store(struct folio *folio) @@ -41,6 +46,10 @@ static inline bool zswap_remove_swpentry_from_lru(swp_entry_t swpentry) static inline void zswap_insert_swpentry_into_lru(swp_entry_t swpentry) {} +static inline bool zswap_bypass_swap_when_store_fail(void) +{ + return false; +} #endif #endif /* _LINUX_ZSWAP_H */ diff --git a/mm/page_io.c b/mm/page_io.c index cb559ae324c6..482f56d27bcd 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -201,6 +201,12 @@ int swap_writepage(struct page *page, struct writeback_control *wbc) folio_end_writeback(folio); return 0; } + + if (zswap_bypass_swap_when_store_fail()) { + folio_mark_dirty(folio); + return AOP_WRITEPAGE_ACTIVATE; + } + __swap_writepage(&folio->page, wbc); return 0; } diff --git a/mm/shmem.c b/mm/shmem.c index 6503910b0f54..8614d7fbe18c 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1514,8 +1514,12 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) mutex_unlock(&shmem_swaplist_mutex); BUG_ON(folio_mapped(folio)); - swap_writepage(&folio->page, wbc); - return 0; + /* + * Seeing AOP_WRITEPAGE_ACTIVATE here indicates swapping is disabled on + * zswap store failure. Note that in that case the folio is already + * re-marked dirty by swap_writepage() + */ + return swap_writepage(&folio->page, wbc); } mutex_unlock(&shmem_swaplist_mutex); diff --git a/mm/zswap.c b/mm/zswap.c index d545516fb5de..db2674548670 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -138,6 +138,10 @@ static bool zswap_non_same_filled_pages_enabled = true; module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled, bool, 0644); +bool zswap_bypass_swap_when_store_fail_enabled; +module_param_named(bypass_swap_when_store_fail_enabled, + zswap_bypass_swap_when_store_fail_enabled, bool, 0644); + static bool zswap_exclusive_loads_enabled = IS_ENABLED( CONFIG_ZSWAP_EXCLUSIVE_LOADS_DEFAULT_ON); module_param_named(exclusive_loads, zswap_exclusive_loads_enabled, bool, 0644); -- 2.34.1