From patchwork Fri Oct 2 16:20:48 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Kalesh Singh X-Patchwork-Id: 11813955 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id F17F2112C for ; Fri, 2 Oct 2020 16:21:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BBC6B2168B for ; Fri, 2 Oct 2020 16:21:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Ufd1QrF9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388028AbgJBQVx (ORCPT ); Fri, 2 Oct 2020 12:21:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43676 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726386AbgJBQVx (ORCPT ); Fri, 2 Oct 2020 12:21:53 -0400 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2560C0613E2 for ; Fri, 2 Oct 2020 09:21:52 -0700 (PDT) Received: by mail-qv1-xf4a.google.com with SMTP id a13so1143980qvl.6 for ; Fri, 02 Oct 2020 09:21:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:cc:content-transfer-encoding; bh=I26gE7RK9ILKrxLTmmwKYo9H+xxwOGRhO/1HGYXougo=; b=Ufd1QrF95drosUZdcSt4pt8x9o20oE5gS7M+m92HNSr5FhOhplzPKi1EKI411U9TLo 5SHDbKsUFPpVINF0auMkvh0n0Dtwsw+MaXQi4IYLQW24BiC3livamhQ/dR3QohP+YRUv /bBASK+tzyyn8akUIREStNWvRhV6/Y9ioigmtWfmYPnABMiDEj2wgfKMqCgzEoUdSIbn eUAlh7PKwqiEx15C/1sLIxz8GqQOu3ex46oiba/Wq+jrIUO52RAfMrfKjEuuJ2dLeUkb Zl06/AVEALyEVFrT+Q649JsCMwTL6Weiqqrn0OjbvDOTaaln1U995eZB7bItEr+XlyE6 5Nww== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:cc:content-transfer-encoding; bh=I26gE7RK9ILKrxLTmmwKYo9H+xxwOGRhO/1HGYXougo=; b=GiIQkzrUWkbGfopFmHqfqBrF60kZOJUPjEWJI7AYdzH3CSImGblvyAAWp9+2P+8w+f nusEku/xy/CYgPC3iAUd4jA4lVD7T9lbLXTTRKghVwgZNJGNMv3tZ2Vb5B/nn4KsOusO qYGIxWMylGYas17BJj8QY+1wks0kCpscPOBlokVrQ9O14WkdZMwLv6WQD9+TOgJtDxCB nqMf9S//McR4RBqPnm6qVSHAv/bETdACJR244v/XEaZUecAHCTGQ8DhrfVmV4gqx4RtV WQWM1zvTTVvJJqGLUG4LTTzUR9QcCRTVK0QyJ2lq2lot+rvdMvkCjhqZO7pNDhGYu9MO opOQ== X-Gm-Message-State: AOAM532p8lBq2s2LO/LNogjwi8WanmAregLoIl1RGtxM/0kWtCl6JlKl vKxRgdjw924fAZQh5g60GuivVqz1U0MahpYk/w== X-Google-Smtp-Source: ABdhPJykXtAYCiJ+5f30jiX2izinlG5HRyfaLfY9GZ7qEIRpP6fH+mi3w22eaAhavH5xmtsIqpl4qVNUYo0OyZpVEw== Sender: "kaleshsingh via sendgmr" X-Received: from kaleshsingh.c.googlers.com ([fda3:e722:ac3:10:14:4d90:c0a8:2145]) (user=kaleshsingh job=sendgmr) by 2002:a0c:f48e:: with SMTP id i14mr3014041qvm.9.1601655711956; Fri, 02 Oct 2020 09:21:51 -0700 (PDT) Date: Fri, 2 Oct 2020 16:20:48 +0000 In-Reply-To: <20201002162101.665549-1-kaleshsingh@google.com> Message-Id: <20201002162101.665549-4-kaleshsingh@google.com> Mime-Version: 1.0 References: <20201002162101.665549-1-kaleshsingh@google.com> X-Mailer: git-send-email 2.28.0.806.g8561365e88-goog Subject: [PATCH v2 3/6] mm: Speedup mremap on 1GB or larger regions From: Kalesh Singh Cc: surenb@google.com, minchan@google.com, joelaf@google.com, lokeshgidra@google.com, kaleshsingh@google.com, kernel-team@android.com, kernel test robot , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Andrew Morton , Shuah Khan , "Aneesh Kumar K.V" , Kees Cook , Peter Zijlstra , Sami Tolvanen , Masahiro Yamada , Arnd Bergmann , Frederic Weisbecker , Krzysztof Kozlowski , Hassan Naveed , Christian Brauner , Mark Rutland , Mike Rapoport , Gavin Shan , Chris von Recklinghausen , Jia He , Zhenyu Ye , John Hubbard , Thiago Jung Bauermann , "Kirill A. Shutemov" , William Kucharski , Ram Pai , Ralph Campbell , Mina Almasry , Sandipan Das , Dave Hansen , Masami Hiramatsu , SeongJae Park , Brian Geffon , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Android needs to move large memory regions for garbage collection. The GC requires moving physical pages of multi-gigabyte heap using mremap. During this move, the application threads have to be paused for correctness. It is critical to keep this pause as short as possible to avoid jitters during user interaction. Optimize mremap for >= 1GB-sized regions by moving at the PUD/PGD level if the source and destination addresses are PUD-aligned. For CONFIG_PGTABLE_LEVELS == 3, moving at the PUD level in effect moves PGD entries, since the PUD entry is “folded back” onto the PGD entry. Add HAVE_MOVE_PUD so that architectures where moving at the PUD level isn't supported/tested can turn this off by not selecting the config. Fix build test error from v1 of this series reported by kernel test robot in [1]. [1] https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/CKPGL4FH4NG7TGH2CVYX2UX76L25BTA3/ Signed-off-by: Kalesh Singh Reported-by: kernel test robot --- Changes in v2: - Update commit message with description of Android GC's use case. - Move set_pud_at() to a separate patch. - Use switch() instead of ifs in move_pgt_entry() - Fix build test error reported by kernel test robot on x86_64 in [1]. Guard move_huge_pmd() with IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE), since this section doesn't get optimized out in the kernel test robot's build test when HAVE_MOVE_PUD is enabled. - Keep WARN_ON_ONCE(1) instead of BUILD_BUG() for the aforementioned reason. arch/Kconfig | 7 ++ mm/mremap.c | 220 ++++++++++++++++++++++++++++++++++++++++++++------- 2 files changed, 197 insertions(+), 30 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index af14a567b493..5eabaa00bf9b 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -602,6 +602,13 @@ config HAVE_IRQ_TIME_ACCOUNTING Archs need to ensure they use a high enough resolution clock to support irq time accounting and then call enable_sched_clock_irqtime(). +config HAVE_MOVE_PUD + bool + help + Architectures that select this are able to move page tables at the + PUD level. If there are only 3 page table levels, the move effectively + happens at the PGD level. + config HAVE_MOVE_PMD bool help diff --git a/mm/mremap.c b/mm/mremap.c index 138abbae4f75..c1d6ab667d70 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -249,14 +249,176 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, return true; } +#else +static inline bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, + unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd) +{ + return false; +} #endif +#ifdef CONFIG_HAVE_MOVE_PUD +static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + + pgd = pgd_offset(mm, addr); + if (pgd_none_or_clear_bad(pgd)) + return NULL; + + p4d = p4d_offset(pgd, addr); + if (p4d_none_or_clear_bad(p4d)) + return NULL; + + pud = pud_offset(p4d, addr); + if (pud_none_or_clear_bad(pud)) + return NULL; + + return pud; +} + +static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long addr) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + + pgd = pgd_offset(mm, addr); + p4d = p4d_alloc(mm, pgd, addr); + if (!p4d) + return NULL; + pud = pud_alloc(mm, p4d, addr); + if (!pud) + return NULL; + + return pud; +} + +static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr, + unsigned long new_addr, pud_t *old_pud, pud_t *new_pud) +{ + spinlock_t *old_ptl, *new_ptl; + struct mm_struct *mm = vma->vm_mm; + pud_t pud; + + /* + * The destination pud shouldn't be established, free_pgtables() + * should have released it. + */ + if (WARN_ON_ONCE(!pud_none(*new_pud))) + return false; + + /* + * We don't have to worry about the ordering of src and dst + * ptlocks because exclusive mmap_lock prevents deadlock. + */ + old_ptl = pud_lock(vma->vm_mm, old_pud); + new_ptl = pud_lockptr(mm, new_pud); + if (new_ptl != old_ptl) + spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); + + /* Clear the pud */ + pud = *old_pud; + pud_clear(old_pud); + + VM_BUG_ON(!pud_none(*new_pud)); + + /* Set the new pud */ + set_pud_at(mm, new_addr, new_pud, pud); + flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE); + if (new_ptl != old_ptl) + spin_unlock(new_ptl); + spin_unlock(old_ptl); + + return true; +} +#else +static inline bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr, + unsigned long new_addr, pud_t *old_pud, pud_t *new_pud) +{ + return false; +} +#endif + +enum pgt_entry { + NORMAL_PMD, + HPAGE_PMD, + NORMAL_PUD, +}; + +/* + * Returns an extent of the corresponding size for the pgt_entry specified if valid. + * Else returns a smaller extent bounded by the end of the source and destination + * pgt_entry. Returns 0 if an invalid pgt_entry is specified. + */ +static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr, + unsigned long old_end, unsigned long new_addr) +{ + unsigned long next, extent, mask, size; + + if (entry == NORMAL_PMD || entry == HPAGE_PMD) { + mask = PMD_MASK; + size = PMD_SIZE; + } else if (entry == NORMAL_PUD) { + mask = PUD_MASK; + size = PUD_SIZE; + } else + return 0; + + next = (old_addr + size) & mask; + /* even if next overflowed, extent below will be ok */ + extent = (next > old_end) ? old_end - old_addr : next - old_addr; + next = (new_addr + size) & mask; + if (extent > next - new_addr) + extent = next - new_addr; + return extent; +} + +/* + * Attempts to speedup the move by moving entry at the level corresponding to + * pgt_entry. Returns true if the move was successful, else false. + */ +static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma, + unsigned long old_addr, unsigned long new_addr, void *old_entry, + void *new_entry, bool need_rmap_locks) +{ + bool moved = false; + + /* See comment in move_ptes() */ + if (need_rmap_locks) + take_rmap_locks(vma); + + switch (entry) { + case NORMAL_PMD: + moved = move_normal_pmd(vma, old_addr, new_addr, old_entry, new_entry); + break; + case NORMAL_PUD: + moved = move_normal_pud(vma, old_addr, new_addr, old_entry, new_entry); + break; + case HPAGE_PMD: + moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && + move_huge_pmd(vma, old_addr, new_addr, old_entry, new_entry); + break; + default: + WARN_ON_ONCE(1); + break; + } + + if (need_rmap_locks) + drop_rmap_locks(vma); + + return moved; +} + unsigned long move_page_tables(struct vm_area_struct *vma, unsigned long old_addr, struct vm_area_struct *new_vma, unsigned long new_addr, unsigned long len, bool need_rmap_locks) { - unsigned long extent, next, old_end; + unsigned long extent, old_end; struct mmu_notifier_range range; pmd_t *old_pmd, *new_pmd; @@ -269,14 +431,27 @@ unsigned long move_page_tables(struct vm_area_struct *vma, for (; old_addr < old_end; old_addr += extent, new_addr += extent) { cond_resched(); - next = (old_addr + PMD_SIZE) & PMD_MASK; - /* even if next overflowed, extent below will be ok */ - extent = next - old_addr; - if (extent > old_end - old_addr) - extent = old_end - old_addr; - next = (new_addr + PMD_SIZE) & PMD_MASK; - if (extent > next - new_addr) - extent = next - new_addr; +#ifdef CONFIG_HAVE_MOVE_PUD + /* + * If extent is PUD-sized try to speed up the move by moving at the + * PUD level if possible. + */ + extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr); + if (extent == PUD_SIZE) { + pud_t *old_pud, *new_pud; + + old_pud = get_old_pud(vma->vm_mm, old_addr); + if (!old_pud) + continue; + new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr); + if (!new_pud) + break; + if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr, + old_pud, new_pud, need_rmap_locks)) + continue; + } +#endif + extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr); old_pmd = get_old_pmd(vma->vm_mm, old_addr); if (!old_pmd) continue; @@ -284,18 +459,10 @@ unsigned long move_page_tables(struct vm_area_struct *vma, if (!new_pmd) break; if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) { - if (extent == HPAGE_PMD_SIZE) { - bool moved; - /* See comment in move_ptes() */ - if (need_rmap_locks) - take_rmap_locks(vma); - moved = move_huge_pmd(vma, old_addr, new_addr, - old_pmd, new_pmd); - if (need_rmap_locks) - drop_rmap_locks(vma); - if (moved) - continue; - } + if (extent == HPAGE_PMD_SIZE && + move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr, old_pmd, + new_pmd, need_rmap_locks)) + continue; split_huge_pmd(vma, old_pmd, old_addr); if (pmd_trans_unstable(old_pmd)) continue; @@ -305,15 +472,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma, * If the extent is PMD-sized, try to speed the move by * moving at the PMD level if possible. */ - bool moved; - - if (need_rmap_locks) - take_rmap_locks(vma); - moved = move_normal_pmd(vma, old_addr, new_addr, - old_pmd, new_pmd); - if (need_rmap_locks) - drop_rmap_locks(vma); - if (moved) + if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr, old_pmd, + new_pmd, need_rmap_locks)) continue; #endif }