From nobody Fri Dec 19 07:18:07 2025 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 2631BC04AA5 for ; Thu, 25 Aug 2022 10:12:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239719AbiHYKM6 (ORCPT ); Thu, 25 Aug 2022 06:12:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241075AbiHYKMW (ORCPT ); Thu, 25 Aug 2022 06:12:22 -0400 Received: from mail-pg1-x536.google.com (mail-pg1-x536.google.com [IPv6:2607:f8b0:4864:20::536]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9FA7BAC259 for ; Thu, 25 Aug 2022 03:12:12 -0700 (PDT) Received: by mail-pg1-x536.google.com with SMTP id r22so17459474pgm.5 for ; Thu, 25 Aug 2022 03:12:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc; bh=4+N7HYlfplazgpIqzrok71tJ5+HL03OgoPpZtaJJ/JA=; b=Bu7SsRr4s/1augCft2+vJK75ZrctEK6Iyfqu3Pqt47wpkqwjMjUrUC1JkgguNrwL13 2hwv5VLcCfH+1TdJctlmV4tEW0D5p2uuFLXfW83lWXUXrRqn7wVkKO6VfJ+TG0znQv03 iVFjsT+BlKjd/AFLzEoJHLCxK2LgbnhjLHjQ2I0kzLOzbt/5nN04MawaWeD4I0Qm64w2 E9MSbNuPJ3pLKOYKGmuvPUahHRz+8UnEMIUSOM24Pd3OQIg9OBXQ7WM9H2O2mD3CUq/L a6iPYt/Xvmok3ln2e30SBo3/3tTpT4vmSws68CmrOOrJk1agvp1haB8koBrCgA4j8OJl 16qg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc; bh=4+N7HYlfplazgpIqzrok71tJ5+HL03OgoPpZtaJJ/JA=; b=CObyG5vZjYIbGsWq5dQjmkYIvk9eGN307sThcjOObpIwkGNAmJPbCIs7EuYAaVRzme zbwip5WXmPCbMJtk9qZVJRr4NKOg6ISFt9VbnfyjI9R+kJ8Yh6m9l89HE0SeIPFuhCDs gBAK4j2C3uN6wzH+RuxRVEXgAXQihczS0uTJp0aP3J1bpljkrsUcf648ERmz653NoHiU GYEydptuMOyr9m6FozsCJYFOf83Ak8D3v6cOFWqQUkRViRbbJpWMRJ9j4ngtXb5pnf73 x3UwAOZSD86fEtsZW9jisqgbWqaafmbCNSt3xwwU2ovhHqa/8bioxEYFHvqUCyoHjX9O fUSA== X-Gm-Message-State: ACgBeo3JiPpNJPpDuQqC7yFtRK238dIL16KX29VUNRUt4aT53GrDN4/0 4j5wvWC9vcMiPrnfmLUbKprCkg== X-Google-Smtp-Source: AA6agR4E8A9z3wJppoQNhY57GIv03JlBORZW3VAf7AyAGpWyEGHzTY8vAaMpe8BdYq7iY2OzpCD70Q== X-Received: by 2002:a63:e851:0:b0:42a:3bc0:9ad1 with SMTP id a17-20020a63e851000000b0042a3bc09ad1mr2612576pgk.543.1661422332147; Thu, 25 Aug 2022 03:12:12 -0700 (PDT) Received: from C02DW0BEMD6R.bytedance.net ([139.177.225.234]) by smtp.gmail.com with ESMTPSA id b10-20020a170903228a00b001714c36a6e7sm8477581plh.284.2022.08.25.03.12.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Aug 2022 03:12:11 -0700 (PDT) From: Qi Zheng To: akpm@linux-foundation.org, david@redhat.com, kirill.shutemov@linux.intel.com, mika.penttila@nextfour.com, jgg@nvidia.com, tglx@linutronix.de, willy@infradead.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, muchun.song@linux.dev, Qi Zheng Subject: [RFC PATCH 7/7] mm: add proc interface to free user PTE page table pages Date: Thu, 25 Aug 2022 18:10:37 +0800 Message-Id: <20220825101037.96517-8-zhengqi.arch@bytedance.com> X-Mailer: git-send-email 2.24.3 (Apple Git-128) In-Reply-To: <20220825101037.96517-1-zhengqi.arch@bytedance.com> References: <20220825101037.96517-1-zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Add /proc/sys/vm/free_ptes file to procfs, when pid is written to the file, we will traverse its process address space, find and free empty PTE pages or zero PTE pages. Signed-off-by: Qi Zheng --- include/linux/pte_ref.h | 5 ++ kernel/sysctl.c | 12 ++++ mm/pte_ref.c | 126 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 143 insertions(+) diff --git a/include/linux/pte_ref.h b/include/linux/pte_ref.h index ab49c7fac120..f7e244129291 100644 --- a/include/linux/pte_ref.h +++ b/include/linux/pte_ref.h @@ -16,6 +16,11 @@ void track_pte_set(struct mm_struct *mm, unsigned long a= ddr, pte_t *ptep, pte_t pte); void track_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte); + +int free_ptes_sysctl_handler(struct ctl_table *table, int write, + void *buffer, size_t *length, loff_t *ppos); +extern int sysctl_free_ptes_pid; + #else /* !CONFIG_FREE_USER_PTE */ =20 static inline void pte_ref_init(pgtable_t pte) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 35d034219513..14e1a9841cb8 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -64,6 +64,7 @@ #include #include #include +#include =20 #include "../lib/kstrtox.h" =20 @@ -2153,6 +2154,17 @@ static struct ctl_table vm_table[] =3D { .extra1 =3D SYSCTL_ONE, .extra2 =3D SYSCTL_FOUR, }, +#ifdef CONFIG_FREE_USER_PTE + { + .procname =3D "free_ptes", + .data =3D &sysctl_free_ptes_pid, + .maxlen =3D sizeof(int), + .mode =3D 0200, + .proc_handler =3D free_ptes_sysctl_handler, + .extra1 =3D SYSCTL_ZERO, + .extra2 =3D SYSCTL_INT_MAX, + }, +#endif #ifdef CONFIG_COMPACTION { .procname =3D "compact_memory", diff --git a/mm/pte_ref.c b/mm/pte_ref.c index 818821d068af..e7080a3100a6 100644 --- a/mm/pte_ref.c +++ b/mm/pte_ref.c @@ -6,6 +6,14 @@ */ #include #include +#include +#include +#include +#include +#include +#include + +#include "internal.h" =20 #ifdef CONFIG_FREE_USER_PTE =20 @@ -105,4 +113,122 @@ void track_pte_clear(struct mm_struct *mm, unsigned l= ong addr, pte_t *ptep, } EXPORT_SYMBOL(track_pte_clear); =20 +#ifdef CONFIG_DEBUG_VM +void pte_free_debug(pmd_t pmd) +{ + pte_t *ptep =3D (pte_t *)pmd_page_vaddr(pmd); + int i =3D 0; + + for (i =3D 0; i < PTRS_PER_PTE; i++, ptep++) { + pte_t pte =3D *ptep; + BUG_ON(!(pte_none(pte) || is_zero_pfn(pte_pfn(pte)))); + } +} +#else +static inline void pte_free_debug(pmd_t pmd) +{ +} +#endif + + +static int kfreeptd_pmd_entry(pmd_t *pmd, unsigned long addr, + unsigned long next, struct mm_walk *walk) +{ + pmd_t pmdval; + pgtable_t page; + struct mm_struct *mm =3D walk->mm; + struct vm_area_struct vma =3D TLB_FLUSH_VMA(mm, 0); + spinlock_t *ptl; + bool free =3D false; + unsigned long haddr =3D addr & PMD_MASK; + + if (pmd_trans_unstable(pmd)) + goto out; + + mmap_read_unlock(mm); + mmap_write_lock(mm); + + if (mm_find_pmd(mm, addr) !=3D pmd) + goto unlock_out; + + ptl =3D pmd_lock(mm, pmd); + pmdval =3D *pmd; + if (pmd_none(pmdval) || pmd_leaf(pmdval)) { + spin_unlock(ptl); + goto unlock_out; + } + page =3D pmd_pgtable(pmdval); + if (!pte_mapped_count(page) || pte_zero_count(page) =3D=3D PTRS_PER_PTE) { + pmd_clear(pmd); + flush_tlb_range(&vma, haddr, haddr + PMD_SIZE); + free =3D true; + } + spin_unlock(ptl); + +unlock_out: + mmap_write_unlock(mm); + mmap_read_lock(mm); + + if (free) { + pte_free_debug(pmdval); + mm_dec_nr_ptes(mm); + pgtable_pte_page_dtor(page); + __free_page(page); + } + +out: + cond_resched(); + return 0; +} + +static const struct mm_walk_ops kfreeptd_walk_ops =3D { + .pmd_entry =3D kfreeptd_pmd_entry, +}; + +int sysctl_free_ptes_pid; +int free_ptes_sysctl_handler(struct ctl_table *table, int write, + void *buffer, size_t *length, loff_t *ppos) +{ + int ret; + + ret =3D proc_dointvec_minmax(table, write, buffer, length, ppos); + if (ret) + return ret; + if (write) { + struct task_struct *task; + struct mm_struct *mm; + + rcu_read_lock(); + task =3D find_task_by_vpid(sysctl_free_ptes_pid); + if (!task) { + rcu_read_unlock(); + return -ESRCH; + } + mm =3D get_task_mm(task); + rcu_read_unlock(); + + if (!mm) { + mmput(mm); + return -ESRCH; + } + + do { + ret =3D -EBUSY; + + if (mmap_read_trylock(mm)) { + ret =3D walk_page_range(mm, FIRST_USER_ADDRESS, + ULONG_MAX, + &kfreeptd_walk_ops, NULL); + + mmap_read_unlock(mm); + } + + cond_resched(); + } while (ret =3D=3D -EAGAIN); + + mmput(mm); + } + return ret; +} + #endif /* CONFIG_FREE_USER_PTE */ --=20 2.20.1