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[217.140.101.70]) by mx.google.com with ESMTP id f16si769441ede.53.2019.05.15.00.41.42 for ; Wed, 15 May 2019 00:41:42 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 941F1374; Wed, 15 May 2019 00:41:41 -0700 (PDT) Received: from [10.163.1.137] (unknown [10.163.1.137]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5B9F93F71E; Wed, 15 May 2019 00:41:36 -0700 (PDT) Subject: Re: [PATCH] mm: refactor __vunmap() to avoid duplicated call to find_vm_area() To: Roman Gushchin , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Johannes Weiner , Matthew Wilcox , Vlastimil Babka References: <20190514235111.2817276-1-guro@fb.com> From: Anshuman Khandual Message-ID: <7ad2b16d-c1a3-b826-df4d-6d9ed1d9fc9f@arm.com> Date: Wed, 15 May 2019 13:11:46 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190514235111.2817276-1-guro@fb.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: On 05/15/2019 05:21 AM, Roman Gushchin wrote: > __vunmap() calls find_vm_area() twice without an obvious reason: > first directly to get the area pointer, second indirectly by calling > vm_remove_mappings()->remove_vm_area(), which is again searching > for the area. > > To remove this redundancy, let's split remove_vm_area() into > __remove_vm_area(struct vmap_area *), which performs the actual area > removal, and remove_vm_area(const void *addr) wrapper, which can > be used everywhere, where it has been used before. Let's pass > a pointer to the vm_area instead of vm_struct to vm_remove_mappings(), > so it can pass it to __remove_vm_area() and avoid the redundant area > lookup. > > On my test setup, I've got 5-10% speed up on vfree()'ing 1000000 > of 4-pages vmalloc blocks. > > Perf report before: > 29.44% cat [kernel.kallsyms] [k] free_unref_page > 11.88% cat [kernel.kallsyms] [k] find_vmap_area > 9.28% cat [kernel.kallsyms] [k] __free_pages > 7.44% cat [kernel.kallsyms] [k] __slab_free > 7.28% cat [kernel.kallsyms] [k] vunmap_page_range > 4.56% cat [kernel.kallsyms] [k] __vunmap > 3.64% cat [kernel.kallsyms] [k] __purge_vmap_area_lazy > 3.04% cat [kernel.kallsyms] [k] __free_vmap_area > > Perf report after: > 32.41% cat [kernel.kallsyms] [k] free_unref_page > 7.79% cat [kernel.kallsyms] [k] find_vmap_area > 7.40% cat [kernel.kallsyms] [k] __slab_free > 7.31% cat [kernel.kallsyms] [k] vunmap_page_range > 6.84% cat [kernel.kallsyms] [k] __free_pages > 6.01% cat [kernel.kallsyms] [k] __vunmap > 3.98% cat [kernel.kallsyms] [k] smp_call_function_single > 3.81% cat [kernel.kallsyms] [k] __purge_vmap_area_lazy > 2.77% cat [kernel.kallsyms] [k] __free_vmap_area > > Signed-off-by: Roman Gushchin > Cc: Johannes Weiner > Cc: Matthew Wilcox > Cc: Vlastimil Babka > --- > mm/vmalloc.c | 52 +++++++++++++++++++++++++++++----------------------- > 1 file changed, 29 insertions(+), 23 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index c42872ed82ac..8d4907865614 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2075,6 +2075,22 @@ struct vm_struct *find_vm_area(const void *addr) > return NULL; > } > > +static struct vm_struct *__remove_vm_area(struct vmap_area *va) > +{ > + struct vm_struct *vm = va->vm; > + > + spin_lock(&vmap_area_lock); > + va->vm = NULL; > + va->flags &= ~VM_VM_AREA; > + va->flags |= VM_LAZY_FREE; > + spin_unlock(&vmap_area_lock); > + > + kasan_free_shadow(vm); > + free_unmap_vmap_area(va); > + > + return vm; > +} > + > /** > * remove_vm_area - find and remove a continuous kernel virtual area > * @addr: base address > @@ -2087,26 +2103,14 @@ struct vm_struct *find_vm_area(const void *addr) > */ > struct vm_struct *remove_vm_area(const void *addr) > { > + struct vm_struct *vm = NULL; > struct vmap_area *va; > > - might_sleep(); Is not this necessary any more ? > - > va = find_vmap_area((unsigned long)addr); > - if (va && va->flags & VM_VM_AREA) { > - struct vm_struct *vm = va->vm; > - > - spin_lock(&vmap_area_lock); > - va->vm = NULL; > - va->flags &= ~VM_VM_AREA; > - va->flags |= VM_LAZY_FREE; > - spin_unlock(&vmap_area_lock); > - > - kasan_free_shadow(vm); > - free_unmap_vmap_area(va); > + if (va && va->flags & VM_VM_AREA) > + vm = __remove_vm_area(va); > > - return vm; > - } > - return NULL; > + return vm; > } Other callers of remove_vm_area() cannot use __remove_vm_area() directly as well to save a look up ?