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Shutemov" To: "Joel Fernandes (Google)" Subject: Re: [PATCH 2/4] mm: speed up mremap by 500x on large regions (v2) Message-ID: <20181024101255.it4lptrjogalxbey@kshutemo-mobl1> References: <20181013013200.206928-1-joel@joelfernandes.org> <20181013013200.206928-3-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181013013200.206928-3-joel@joelfernandes.org> User-Agent: NeoMutt/20180716 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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, sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, elfring@users.sourceforge.net, Jonas Bonn , kvmarm@lists.cs.columbia.edu, dancol@google.com, Yoshinori Sato , 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-begemot.co.uk, Ingo Molnar , Geert Uytterhoeven , Andrey Ryabinin , linux-snps-arc@lists.infradead.org, kernel-team@android.com, Sam Creasey , Fenghua Yu , linux-s390@vger.kernel.org, Jeff Dike , linux-um@lists.infradead.org, Stefan Kristiansson , Julia Lawall , linux-m68k@lists.linux-m68k.org, Borislav Petkov , Andy Lutomirski , nios2-dev@lists.rocketboards.org, Stafford Horne , Guan Xuetao , Chris Zankel , Tony Luck , Richard Weinberger , linux-parisc@vger.kernel.org, pantin@google.com, Max Filippov , linux-kernel@vger.kernel.org, minchan@kernel.org, Thomas Gleixner , linux-alpha@vger.kernel.org, Ley Foon Tan , akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, "David S. Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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); > + 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