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Fri, 19 Apr 2024 11:00:46 +0800 Message-ID: Date: Fri, 19 Apr 2024 11:00:46 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: memory: check userfaultfd_wp() in vmf_orig_pte_uffd_wp() Content-Language: en-US To: Peter Xu CC: Andrew Morton , References: <20240418120641.2653165-1-wangkefeng.wang@huawei.com> From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm100001.china.huawei.com (7.185.36.93) X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A0CA34000F X-Rspam-User: X-Stat-Signature: zjhweju1k8gmi1hqnqgwnjnrj7d8z91e X-HE-Tag: 1713495651-230728 X-HE-Meta: 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 VGNrF8Vr UMVzLJQipjUXvroM9rtQ/+eH3qJy4fO3qvFXtcDm3k4amI0Lb+LKLwOpWwIulwCinNlC7hniWEMo5xQyzXOw0k+S45g10jvPQfKIRbqat/HHGilHSWgPRfYYsi37OHeK55ze1jt2KE7TRjB903egXjKHh+V00NW7+KUt2dyA5KAu/6qm5xKv+n3aXBka/xghJpyZ+v93Pw2zeUgnM/rYmRmH/aw== 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: List-Subscribe: List-Unsubscribe: On 2024/4/19 0:32, Peter Xu wrote: > Hi, Kefeng, > > On Thu, Apr 18, 2024 at 08:06:41PM +0800, Kefeng Wang wrote: >> Add userfaultfd_wp() check in vmf_orig_pte_uffd_wp() to avoid the >> unnecessary pte_marker_entry_uffd_wp() in most pagefault, difference >> as shows below from perf data of lat_pagefault, note, the function >> vmf_orig_pte_uffd_wp() is not inlined in the two kernel versions. >> >> perf report -i perf.data.before | grep vmf >> 0.17% 0.13% lat_pagefault [kernel.kallsyms] [k] vmf_orig_pte_uffd_wp.part.0.isra.0 >> perf report -i perf.data.after | grep vmf > > Any real number to share too besides the perf greps? I meant, even if perf > report will not report such function anymore, it doesn't mean it'll be > faster, and how much it improves? dd if=/dev/zero of=/tmp/XXX bs=512M count=1 ./lat_pagefault -W 5 -N 5 /tmp/XXX before after 1 0.2623 0.2605 2 0.2622 0.2598 3 0.2621 0.2595 4 0.2622 0.2600 5 0.2651 0.2598 6 0.2624 0.2594 7 0.2624 0.2605 8 0.2627 0.2608 average 0.262675 0.2600375 -0.0026375 The lat_pagefault does show some improvement(also I reboot and retest, the results are same). > > Now we're switching from pte_marker_uffd_wp() check into a vma flag check. > I think it makes more sense to compare the number rather than the perf > reports, as the vma flag check instructions will be buried under other > entries IIUC. > > Thanks, >