From mboxrd@z Thu Jan 1 00:00:00 1970 From: Balbir Singh Subject: Re: [PATCH 2/4] mm: speed up mremap by 500x on large regions (v2) Date: Wed, 24 Oct 2018 22:57:33 +1100 Message-ID: <20181024115733.GN8537@350D> References: <20181013013200.206928-1-joel@joelfernandes.org> <20181013013200.206928-3-joel@joelfernandes.org> <20181024101255.it4lptrjogalxbey@kshutemo-mobl1> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=AoCHhnV3ilCup/gmvoTVu2odieWR8T1veLyePwG53v8=; b=mzSbEJ4BrQyIqW byVPpzWaQncsH6LaQOIiARAeF1c4+pYl8i8i0IQipSU7nHyLpvm5gItQG20FYArwzK2Z520/fO7ZR 7NwR9vgeYld5VamRVOOOAFwXDyIUvQw9J2DBaZLqwZFIUcDOUSOeASqPZk/cnm5TgpsAu0Vg+dYnW ra567mcKdBEJQZNfcccbiqVXLst6Z9VQIZ9rv6RW3AZZLaYiM3FaJXUKtsFFrmS7g9a28rqSXbtFN exZ2n9xI+z6x8EJ96HGmYJt2Ngc3PW+X1Qsi53VCNqq2Rqs7Tvg29tvjCsvvmTzN4GkvOJQRCNWyO eDuNC1/BB0XXiXXnKc3g==; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=r4S1JZtjtEoZRmv1cmbD7oqQ5fBxxZJ0gckdgeOcI14=; b=rxvOMkoPR1fl+wChK1gmiyTy80jYizuSzzLNsN1UW/nn68lcvDelAzg7q5xRULAFwF 88m9+eaacj9fu1oQRgbn9o9rL5OobsROYLsUPy8Jgnz+ao671RDA5Lk1ggZYlGqX9SbG 9RUUixIOumM9W9fFeC11ng0GECm2HV0kpOJEacCyBhFOab2Q3i4VFHF0QbnxQWZzkmCY Lire1m9l7AF9VgUbUKgofuhPxpehLdKNOXRb6mUKntibxqs2pslottwNtAIjzUINJV13 bV4f1WLD9yCA7Iyr+h+lgaNFbMHR6/U4tmHoxnhQ/7prUqBNDcYtn35v7xWxzF+rGnLI 1zrQ== Content-Disposition: inline In-Reply-To: <20181024101255.it4lptrjogalxbey@kshutemo-mobl1> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+gla-linux-snps-arc=m.gmane.org@lists.infradead.org To: "Kirill A. Shutemov" Cc: linux-mips@linux-mips.org, Rich Felker , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , Catalin Marinas , Dave Hansen , Will Deacon , mhocko@kernel.org, linux-mm@kvack.org, lokeshgidra@google.com, "Joel Fernandes (Google)" , linux-riscv@lists.infradead.org, elfring@users.sourceforge.net, Jonas Bonn , kvmarm@lists.cs.columbia.edu, dancol@google.com, Yoshinori Sato , sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-hexagon@vger.kernel.org, Helge Deller , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , hughd@google.com, "James E.J. Bottomley" , kasan-dev@googlegroups.com, anton.ivanov@kot-b On Wed, Oct 24, 2018 at 01:12:56PM +0300, Kirill A. Shutemov wrote: > On Fri, Oct 12, 2018 at 06:31:58PM -0700, Joel Fernandes (Google) wrote: > > diff --git a/mm/mremap.c b/mm/mremap.c > > index 9e68a02a52b1..2fd163cff406 100644 > > --- a/mm/mremap.c > > +++ b/mm/mremap.c > > @@ -191,6 +191,54 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, > > drop_rmap_locks(vma); > > } > > > > +static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, > > + unsigned long new_addr, unsigned long old_end, > > + pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush) > > +{ > > + spinlock_t *old_ptl, *new_ptl; > > + struct mm_struct *mm = vma->vm_mm; > > + > > + if ((old_addr & ~PMD_MASK) || (new_addr & ~PMD_MASK) > > + || old_end - old_addr < PMD_SIZE) > > + return false; > > + > > + /* > > + * The destination pmd shouldn't be established, free_pgtables() > > + * should have release it. > > + */ > > + if (WARN_ON(!pmd_none(*new_pmd))) > > + return false; > > + > > + /* > > + * We don't have to worry about the ordering of src and dst > > + * ptlocks because exclusive mmap_sem prevents deadlock. > > + */ > > + old_ptl = pmd_lock(vma->vm_mm, old_pmd); > > + if (old_ptl) { > > How can it ever be false? > > > + pmd_t pmd; > > + > > + new_ptl = pmd_lockptr(mm, new_pmd); Looks like this is largely inspired by move_huge_pmd(), I guess a lot of the code applies, why not just reuse as much as possible? The same comments w.r.t mmap_sem helping protect against lock order issues applies as well. > > + if (new_ptl != old_ptl) > > + spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); > > + > > + /* Clear the pmd */ > > + pmd = *old_pmd; > > + pmd_clear(old_pmd); > > + > > + VM_BUG_ON(!pmd_none(*new_pmd)); > > + > > + /* Set the new pmd */ > > + set_pmd_at(mm, new_addr, new_pmd, pmd); > > + if (new_ptl != old_ptl) > > + spin_unlock(new_ptl); > > + spin_unlock(old_ptl); > > + > > + *need_flush = true; > > + return true; > > + } > > + return false; > > +} > > + > -- > Kirill A. Shutemov >