From patchwork Mon May 9 06:27:03 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Muchun Song X-Patchwork-Id: 12843064 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 CB59EC433F5 for ; Mon, 9 May 2022 06:29:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 63F376B0078; Mon, 9 May 2022 02:29:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6151E6B007B; Mon, 9 May 2022 02:29:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4B6606B007D; Mon, 9 May 2022 02:29:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 3AF5A6B0078 for ; Mon, 9 May 2022 02:29:41 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 0DB7430098 for ; Mon, 9 May 2022 06:29:41 +0000 (UTC) X-FDA: 79445228562.08.7E207F3 Received: from mail-pj1-f49.google.com (mail-pj1-f49.google.com [209.85.216.49]) by imf05.hostedemail.com (Postfix) with ESMTP id 534FD100092 for ; Mon, 9 May 2022 06:29:24 +0000 (UTC) Received: by mail-pj1-f49.google.com with SMTP id iq10so12282221pjb.0 for ; Sun, 08 May 2022 23:29:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=3vUx5XYnNUQ4SpbVJ4KR5YqsE/7i6GdjQvDrH5RKigc=; b=TC82INHLWZrU49CJ9vAbOyzbFZYnVPtZhj4HVMh0/PQ11kYlduRnmVkgVpkkAmIUnW pp840rF3esS1AZXEMuittuqcKYnRssv1NCAHX+11MQu2rVZIYkFqwWTuqOqgiwjCNnBB gdieRlCPhZ+IRj3xCyGAW1f3VK5ARJswXCwe76rmm0+I4sLIkCfkOQfdIDsxEfT4U7Dk hACf8ULMirNyXDDJb1zw8YIoWhcmMXEMNjJxn3cd3XDd3M7dlOUFpz3jpcz1xnuXtzcA kiAErI82e+jpbRnHXUxTgoNhziz8XhCLewLt0JtkWY8bFQn2IRNUTQr9/ZbaaK4lnTKd +a2w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=3vUx5XYnNUQ4SpbVJ4KR5YqsE/7i6GdjQvDrH5RKigc=; b=VH8O3k4V23m3vFB9UFiWwX6sE3DFfo/PBiJONpsAK0ak6vV4/aIrOp60vSAssMqOms bAt41sex+0wqjWQD5m1tUkppmdKPF5HxZv7Y+C7ZoKafU5B8LPhkWzbPoIliJ3BW2JXY fYbJeJu5A6nxvaBlMcdjKduyBAHtM3K6MG7L+rtJPp6g3gmR4C8u4ddaXGhlwWpUvIYo hpXqI7Lr21zwN9Xml9+02AiUY1xa+4wJg+TzRudYYj6bBPWBvLhhNb5K/1l7o0OiIWx3 +rwu4BYoNOF9b2V9w71DNvXRK8Fae6cLpemXdf1bOCMofb1JLqJAZmWgAKN50dSXDbg5 9New== X-Gm-Message-State: AOAM533YUSoxCvsJ47bk2f/t/QdJUMXbrQBT/kGKbfBRMeVfguay3szg NQxQd/O1aFONlfmoPbcJUZbnkg== X-Google-Smtp-Source: ABdhPJysbt69R8xvl2WHk4ESD/nLQCAsz2esg98Qalvazq3o1Jn35yLaPmDEGrRWUUQboLjeHbYzwg== X-Received: by 2002:a17:903:1210:b0:15e:8373:d4b8 with SMTP id l16-20020a170903121000b0015e8373d4b8mr14867375plh.11.1652077779569; Sun, 08 May 2022 23:29:39 -0700 (PDT) Received: from FVFYT0MHHV2J.bytedance.net ([139.177.225.250]) by smtp.gmail.com with ESMTPSA id k17-20020a170902ba9100b0015e8d4eb2c2sm6162001pls.268.2022.05.08.23.29.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 May 2022 23:29:39 -0700 (PDT) From: Muchun Song To: corbet@lwn.net, mike.kravetz@oracle.com, akpm@linux-foundation.org, mcgrof@kernel.org, keescook@chromium.org, yzaikin@google.com, osalvador@suse.de, david@redhat.com, masahiroy@kernel.org Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com, Muchun Song Subject: [PATCH v10 4/4] mm: hugetlb_vmemmap: add hugetlb_optimize_vmemmap sysctl Date: Mon, 9 May 2022 14:27:03 +0800 Message-Id: <20220509062703.64249-5-songmuchun@bytedance.com> X-Mailer: git-send-email 2.32.0 (Apple Git-132) In-Reply-To: <20220509062703.64249-1-songmuchun@bytedance.com> References: <20220509062703.64249-1-songmuchun@bytedance.com> MIME-Version: 1.0 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 534FD100092 X-Stat-Signature: hkymot3hjjx9nu7fbyxooeznkfh8dm1a Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=TC82INHL; dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf05.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.216.49 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-Rspam-User: X-HE-Tag: 1652077764-69176 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: We must add hugetlb_free_vmemmap=on (or "off") to the boot cmdline and reboot the server to enable or disable the feature of optimizing vmemmap pages associated with HugeTLB pages. However, rebooting usually takes a long time. So add a sysctl to enable or disable the feature at runtime without rebooting. Why we need this? There are 3 use cases. 1) The feature of minimizing overhead of struct page associated with each HugeTLB is disabled by default without passing "hugetlb_free_vmemmap=on" to the boot cmdline. When we (ByteDance) deliver the servers to the users who want to enable this feature, they have to configure the grub (change boot cmdline) and reboot the servers, whereas rebooting usually takes a long time (we have thousands of servers). It's a very bad experience for the users. So we need a approach to enable this feature after rebooting. This is a use case in our practical environment. 2) Some use cases are that HugeTLB pages are allocated 'on the fly' instead of being pulled from the HugeTLB pool, those workloads would be affected with this feature enabled. Those workloads could be identified by the characteristics of they never explicitly allocating huge pages with 'nr_hugepages' but only set 'nr_overcommit_hugepages' and then let the pages be allocated from the buddy allocator at fault time. We can confirm it is a real use case from the commit 099730d67417. For those workloads, the page fault time could be ~2x slower than before. We suspect those users want to disable this feature if the system has enabled this before and they don't think the memory savings benefit is enough to make up for the performance drop. 3) If the workload which wants vmemmap pages to be optimized and the workload which wants to set 'nr_overcommit_hugepages' and does not want the extera overhead at fault time when the overcommitted pages be allocated from the buddy allocator are deployed in the same server. The user could enable this feature and set 'nr_hugepages' and 'nr_overcommit_hugepages', then disable the feature. In this case, the overcommited HugeTLB pages will not encounter the extra overhead at fault time. Signed-off-by: Muchun Song Reviewed-by: Mike Kravetz --- Documentation/admin-guide/sysctl/vm.rst | 39 ++++++++++++++ include/linux/memory_hotplug.h | 9 ++++ mm/hugetlb.c | 3 ++ mm/hugetlb_vmemmap.c | 93 +++++++++++++++++++++++++++++---- mm/memory_hotplug.c | 7 +-- 5 files changed, 136 insertions(+), 15 deletions(-) diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index 747e325ebcd0..5c9aa171a0d3 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -562,6 +562,45 @@ Change the minimum size of the hugepage pool. See Documentation/admin-guide/mm/hugetlbpage.rst +hugetlb_optimize_vmemmap +======================== + +This knob is not available when memory_hotplug.memmap_on_memory (kernel parameter) +is configured or the size of 'struct page' (a structure defined in +include/linux/mm_types.h) is not power of two (an unusual system config could +result in this). + +Enable (set to 1) or disable (set to 0) the feature of optimizing vmemmap pages +associated with each HugeTLB page. + +Once enabled, the vmemmap pages of subsequent allocation of HugeTLB pages from +buddy allocator will be optimized (7 pages per 2MB HugeTLB page and 4095 pages +per 1GB HugeTLB page), whereas already allocated HugeTLB pages will not be +optimized. When those optimized HugeTLB pages are freed from the HugeTLB pool +to the buddy allocator, the vmemmap pages representing that range needs to be +remapped again and the vmemmap pages discarded earlier need to be rellocated +again. If your use case is that HugeTLB pages are allocated 'on the fly' (e.g. +never explicitly allocating HugeTLB pages with 'nr_hugepages' but only set +'nr_overcommit_hugepages', those overcommitted HugeTLB pages are allocated 'on +the fly') instead of being pulled from the HugeTLB pool, you should weigh the +benefits of memory savings against the more overhead (~2x slower than before) +of allocation or freeing HugeTLB pages between the HugeTLB pool and the buddy +allocator. Another behavior to note is that if the system is under heavy memory +pressure, it could prevent the user from freeing HugeTLB pages from the HugeTLB +pool to the buddy allocator since the allocation of vmemmap pages could be +failed, you have to retry later if your system encounter this situation. + +Once disabled, the vmemmap pages of subsequent allocation of HugeTLB pages from +buddy allocator will not be optimized meaning the extra overhead at allocation +time from buddy allocator disappears, whereas already optimized HugeTLB pages +will not be affected. If you want to make sure there are no optimized HugeTLB +pages, you can set "nr_hugepages" to 0 first and then disable this. Note that +writing 0 to nr_hugepages will make any "in use" HugeTLB pages become surplus +pages. So, those surplus pages are still optimized until they are no longer +in use. You would need to wait for those surplus pages to be released before +there are no optimized pages in the system. + + nr_hugepages_mempolicy ====================== diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 029fb7e26504..917112661b5c 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -351,4 +351,13 @@ void arch_remove_linear_mapping(u64 start, u64 size); extern bool mhp_supports_memmap_on_memory(unsigned long size); #endif /* CONFIG_MEMORY_HOTPLUG */ +#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY +bool mhp_memmap_on_memory(void); +#else +static inline bool mhp_memmap_on_memory(void) +{ + return false; +} +#endif + #endif /* __LINUX_MEMORY_HOTPLUG_H */ diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 8605d7eb7f5c..86158eb9da70 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1617,6 +1617,9 @@ static DECLARE_WORK(free_hpage_work, free_hpage_workfn); static inline void flush_free_hpage_work(struct hstate *h) { + if (!hugetlb_optimize_vmemmap_enabled()) + return; + if (hugetlb_optimize_vmemmap_pages(h)) flush_work(&free_hpage_work); } diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index cc4ec752ec16..fcd9f7872064 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -10,6 +10,7 @@ */ #define pr_fmt(fmt) "HugeTLB: " fmt +#include #include "hugetlb_vmemmap.h" /* @@ -22,21 +23,40 @@ #define RESERVE_VMEMMAP_NR 1U #define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT) +enum vmemmap_optimize_mode { + VMEMMAP_OPTIMIZE_OFF, + VMEMMAP_OPTIMIZE_ON, +}; + DEFINE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON, hugetlb_optimize_vmemmap_key); EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key); +static enum vmemmap_optimize_mode vmemmap_optimize_mode = + IS_ENABLED(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON); + +static void vmemmap_optimize_mode_switch(enum vmemmap_optimize_mode to) +{ + if (vmemmap_optimize_mode == to) + return; + + if (to == VMEMMAP_OPTIMIZE_OFF) + static_branch_dec(&hugetlb_optimize_vmemmap_key); + else + static_branch_inc(&hugetlb_optimize_vmemmap_key); + WRITE_ONCE(vmemmap_optimize_mode, to); +} + static int __init hugetlb_vmemmap_early_param(char *buf) { bool enable; + enum vmemmap_optimize_mode mode; if (kstrtobool(buf, &enable)) return -EINVAL; - if (enable) - static_branch_enable(&hugetlb_optimize_vmemmap_key); - else - static_branch_disable(&hugetlb_optimize_vmemmap_key); + mode = enable ? VMEMMAP_OPTIMIZE_ON : VMEMMAP_OPTIMIZE_OFF; + vmemmap_optimize_mode_switch(mode); return 0; } @@ -69,8 +89,10 @@ int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head) */ ret = vmemmap_remap_alloc(vmemmap_addr, vmemmap_end, vmemmap_reuse, GFP_KERNEL | __GFP_NORETRY | __GFP_THISNODE); - if (!ret) + if (!ret) { ClearHPageVmemmapOptimized(head); + static_branch_dec(&hugetlb_optimize_vmemmap_key); + } return ret; } @@ -84,6 +106,11 @@ void hugetlb_vmemmap_free(struct hstate *h, struct page *head) if (!vmemmap_pages) return; + if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF) + return; + + static_branch_inc(&hugetlb_optimize_vmemmap_key); + vmemmap_addr += RESERVE_VMEMMAP_SIZE; vmemmap_end = vmemmap_addr + (vmemmap_pages << PAGE_SHIFT); vmemmap_reuse = vmemmap_addr - PAGE_SIZE; @@ -93,7 +120,9 @@ void hugetlb_vmemmap_free(struct hstate *h, struct page *head) * to the page which @vmemmap_reuse is mapped to, then free the pages * which the range [@vmemmap_addr, @vmemmap_end] is mapped to. */ - if (!vmemmap_remap_free(vmemmap_addr, vmemmap_end, vmemmap_reuse)) + if (vmemmap_remap_free(vmemmap_addr, vmemmap_end, vmemmap_reuse)) + static_branch_dec(&hugetlb_optimize_vmemmap_key); + else SetHPageVmemmapOptimized(head); } @@ -110,9 +139,6 @@ void __init hugetlb_vmemmap_init(struct hstate *h) BUILD_BUG_ON(__NR_USED_SUBPAGE >= RESERVE_VMEMMAP_SIZE / sizeof(struct page)); - if (!hugetlb_optimize_vmemmap_enabled()) - return; - if (!is_power_of_2(sizeof(struct page))) { pr_warn_once("cannot optimize vmemmap pages because \"struct page\" crosses page boundaries\n"); static_branch_disable(&hugetlb_optimize_vmemmap_key); @@ -134,3 +160,52 @@ void __init hugetlb_vmemmap_init(struct hstate *h) pr_info("can optimize %d vmemmap pages for %s\n", h->optimize_vmemmap_pages, h->name); } + +#ifdef CONFIG_PROC_SYSCTL +static int hugetlb_optimize_vmemmap_handler(struct ctl_table *table, int write, + void *buffer, size_t *length, + loff_t *ppos) +{ + int ret; + enum vmemmap_optimize_mode mode; + static DEFINE_MUTEX(sysctl_mutex); + + if (write && !capable(CAP_SYS_ADMIN)) + return -EPERM; + + mutex_lock(&sysctl_mutex); + mode = vmemmap_optimize_mode; + table->data = &mode; + ret = proc_dointvec_minmax(table, write, buffer, length, ppos); + if (write && !ret) + vmemmap_optimize_mode_switch(mode); + mutex_unlock(&sysctl_mutex); + + return ret; +} + +static struct ctl_table hugetlb_vmemmap_sysctls[] = { + { + .procname = "hugetlb_optimize_vmemmap", + .maxlen = sizeof(enum vmemmap_optimize_mode), + .mode = 0644, + .proc_handler = hugetlb_optimize_vmemmap_handler, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { } +}; + +static __init int hugetlb_vmemmap_sysctls_init(void) +{ + /* + * If "memory_hotplug.memmap_on_memory" is enabled or "struct page" + * crosses page boundaries, the vmemmap pages cannot be optimized. + */ + if (!mhp_memmap_on_memory() && is_power_of_2(sizeof(struct page))) + register_sysctl_init("vm", hugetlb_vmemmap_sysctls); + + return 0; +} +late_initcall(hugetlb_vmemmap_sysctls_init); +#endif /* CONFIG_PROC_SYSCTL */ diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index a6101ae402f9..c72070cdd055 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -63,15 +63,10 @@ static bool memmap_on_memory __ro_after_init; module_param_cb(memmap_on_memory, &memmap_on_memory_ops, &memmap_on_memory, 0444); MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug"); -static inline bool mhp_memmap_on_memory(void) +bool mhp_memmap_on_memory(void) { return memmap_on_memory; } -#else -static inline bool mhp_memmap_on_memory(void) -{ - return false; -} #endif enum {