From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 312C3C433E6 for ; Thu, 25 Feb 2021 08:41:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9148F64EDC for ; Thu, 25 Feb 2021 08:41:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9148F64EDC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 006008D000E; Thu, 25 Feb 2021 03:41:31 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EFB368D0005; Thu, 25 Feb 2021 03:41:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DE7E18D000E; Thu, 25 Feb 2021 03:41:30 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0166.hostedemail.com [216.40.44.166]) by kanga.kvack.org (Postfix) with ESMTP id C97DC8D0005 for ; Thu, 25 Feb 2021 03:41:30 -0500 (EST) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 9568A18508693 for ; Thu, 25 Feb 2021 08:41:30 +0000 (UTC) X-FDA: 77856146340.28.78DDDB7 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf20.hostedemail.com (Postfix) with ESMTP id C1B03E7 for ; Thu, 25 Feb 2021 08:41:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614242489; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fqVSsomUJyTIz0gYNIicWiu4aghYekNv2Fcx+hAQcqI=; b=T/FSs6fsgWB7zg1Z1FqW7cO1Xgn003odA4qxCdaLaanCk0z7B/l/Nw7S4zSayOlhxvdrFD XZ1/liRqA4z56Phi8EVIKohBU78dSNu/mhbsMg9pMRWuw8kl6QvGgViCf2ssYpCdGyy1Ey 7gdnSlkH6ROavcWJs9MSjPIb5rW8JAQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-598-PdpzTNHiPv2rFA2I1NLbbQ-1; Thu, 25 Feb 2021 03:41:24 -0500 X-MC-Unique: PdpzTNHiPv2rFA2I1NLbbQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 007DA100CCC3; Thu, 25 Feb 2021 08:41:19 +0000 (UTC) Received: from [10.36.114.58] (ovpn-114-58.ams2.redhat.com [10.36.114.58]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1F11318A9E; Thu, 25 Feb 2021 08:41:07 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Arnd Bergmann , Michal Hocko , Oscar Salvador , Matthew Wilcox , Andrea Arcangeli , Minchan Kim , Jann Horn , Jason Gunthorpe , Dave Hansen , Hugh Dickins , Rik van Riel , "Michael S . Tsirkin" , "Kirill A . Shutemov" , Vlastimil Babka , Richard Henderson , Ivan Kokshaysky , Matt Turner , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Chris Zankel , Max Filippov , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org References: <20210217154844.12392-1-david@redhat.com> <4bb9071b-e6c1-a732-0ed6-46aff0eaa70c@redhat.com> Organization: Red Hat GmbH Subject: Re: [PATCH RFC] mm/madvise: introduce MADV_POPULATE to prefault/prealloc memory Message-ID: Date: Thu, 25 Feb 2021 09:41:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <4bb9071b-e6c1-a732-0ed6-46aff0eaa70c@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Stat-Signature: ucu1qmwc6d7odgmnujr9x8xosswnrwt9 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C1B03E7 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf20; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=63.128.21.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614242489-198339 Content-Transfer-Encoding: quoted-printable 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 24.02.21 15:25, David Hildenbrand wrote: >> + tmp_end =3D min_t(unsigned long, end, vma->vm_end); >> + pages =3D populate_vma_page_range(vma, start, tmp_end, &locked); >> + if (!locked) { >> + mmap_read_lock(mm); >> + *prev =3D NULL; >> + vma =3D NULL; >=20 > ^ locked =3D 1; is missing here. >=20 >=20 > --- Simple benchmark --- >=20 > I implemented MADV_POPULATE_READ and MADV_POPULATE_WRITE and performed > some simple measurements to simulate memory preallocation with empty fi= les: >=20 > 1) mmap a 2 MiB/128 MiB/4 GiB region (anonymous, memfd, memfd hugetlb) > 2) Discard all memory using fallocate/madvise > 3) Prefault memory using different approaches and measure the time this > takes. >=20 > I repeat 2)+3) 10 times and compute the average. I only use a single th= read. >=20 > Read: Read from each page a byte. > Write: Write one byte of each page (0). > Read/Write: Read one byte and write the value back for each page > POPULATE: MADV_POPULATE (this patch) > POPULATE_READ: MADV_POPULATE_READ > POPULATE_WRITE: MADV_POPULATE_WRITE >=20 > --- Benchmark results --- >=20 > Measuring 10 iterations each: > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D > 2 MiB MAP_PRIVATE: > ************************************************** > Anonymous : Read : 0.159 ms > Anonymous : Write : 0.244 ms > Anonymous : Read+Write : 0.383 ms > Anonymous : POPULATE : 0.167 ms > Anonymous : POPULATE_READ : 0.064 ms > Anonymous : POPULATE_WRITE : 0.165 ms > Memfd 4 KiB : Read : 0.401 ms > Memfd 4 KiB : Write : 0.056 ms > Memfd 4 KiB : Read+Write : 0.075 ms > Memfd 4 KiB : POPULATE : 0.057 ms > Memfd 4 KiB : POPULATE_READ : 0.337 ms > Memfd 4 KiB : POPULATE_WRITE : 0.056 ms > Memfd 2 MiB : Read : 0.041 ms > Memfd 2 MiB : Write : 0.030 ms > Memfd 2 MiB : Read+Write : 0.031 ms > Memfd 2 MiB : POPULATE : 0.031 ms > Memfd 2 MiB : POPULATE_READ : 0.031 ms > Memfd 2 MiB : POPULATE_WRITE : 0.031 ms > ************************************************** > 2 MiB MAP_SHARED: > ************************************************** > Anonymous : Read : 0.071 ms > Anonymous : Write : 0.181 ms > Anonymous : Read+Write : 0.081 ms > Anonymous : POPULATE : 0.069 ms > Anonymous : POPULATE_READ : 0.069 ms > Anonymous : POPULATE_WRITE : 0.115 ms > Memfd 4 KiB : Read : 0.401 ms > Memfd 4 KiB : Write : 0.351 ms > Memfd 4 KiB : Read+Write : 0.414 ms > Memfd 4 KiB : POPULATE : 0.338 ms > Memfd 4 KiB : POPULATE_READ : 0.339 ms > Memfd 4 KiB : POPULATE_WRITE : 0.279 ms > Memfd 2 MiB : Read : 0.031 ms > Memfd 2 MiB : Write : 0.031 ms > Memfd 2 MiB : Read+Write : 0.031 ms > Memfd 2 MiB : POPULATE : 0.031 ms > Memfd 2 MiB : POPULATE_READ : 0.031 ms > Memfd 2 MiB : POPULATE_WRITE : 0.031 ms > ************************************************** > 128 MiB MAP_PRIVATE: > ************************************************** > Anonymous : Read : 7.517 ms > Anonymous : Write : 22.503 ms > Anonymous : Read+Write : 33.186 ms > Anonymous : POPULATE : 18.381 ms > Anonymous : POPULATE_READ : 3.952 ms > Anonymous : POPULATE_WRITE : 18.354 ms > Memfd 4 KiB : Read : 34.300 ms > Memfd 4 KiB : Write : 4.659 ms > Memfd 4 KiB : Read+Write : 6.531 ms > Memfd 4 KiB : POPULATE : 5.219 ms > Memfd 4 KiB : POPULATE_READ : 29.744 ms > Memfd 4 KiB : POPULATE_WRITE : 5.244 ms > Memfd 2 MiB : Read : 10.228 ms > Memfd 2 MiB : Write : 10.130 ms > Memfd 2 MiB : Read+Write : 10.190 ms > Memfd 2 MiB : POPULATE : 10.007 ms > Memfd 2 MiB : POPULATE_READ : 10.008 ms > Memfd 2 MiB : POPULATE_WRITE : 10.010 ms > ************************************************** > 128 MiB MAP_SHARED: > ************************************************** > Anonymous : Read : 7.295 ms > Anonymous : Write : 15.234 ms > Anonymous : Read+Write : 7.460 ms > Anonymous : POPULATE : 5.196 ms > Anonymous : POPULATE_READ : 5.190 ms > Anonymous : POPULATE_WRITE : 8.245 ms > Memfd 4 KiB : Read : 34.412 ms > Memfd 4 KiB : Write : 30.586 ms > Memfd 4 KiB : Read+Write : 35.157 ms > Memfd 4 KiB : POPULATE : 29.643 ms > Memfd 4 KiB : POPULATE_READ : 29.691 ms > Memfd 4 KiB : POPULATE_WRITE : 25.790 ms > Memfd 2 MiB : Read : 10.210 ms > Memfd 2 MiB : Write : 10.074 ms > Memfd 2 MiB : Read+Write : 10.068 ms > Memfd 2 MiB : POPULATE : 10.034 ms > Memfd 2 MiB : POPULATE_READ : 10.037 ms > Memfd 2 MiB : POPULATE_WRITE : 10.031 ms > ************************************************** > 4096 MiB MAP_PRIVATE: > ************************************************** > Anonymous : Read : 240.947 ms > Anonymous : Write : 712.941 ms > Anonymous : Read+Write : 1027.636 ms > Anonymous : POPULATE : 571.816 ms > Anonymous : POPULATE_READ : 120.215 ms > Anonymous : POPULATE_WRITE : 570.750 ms > Memfd 4 KiB : Read : 1054.739 ms > Memfd 4 KiB : Write : 145.534 ms > Memfd 4 KiB : Read+Write : 202.275 ms > Memfd 4 KiB : POPULATE : 162.597 ms > Memfd 4 KiB : POPULATE_READ : 914.747 ms > Memfd 4 KiB : POPULATE_WRITE : 161.281 ms > Memfd 2 MiB : Read : 351.818 ms > Memfd 2 MiB : Write : 352.357 ms > Memfd 2 MiB : Read+Write : 352.762 ms > Memfd 2 MiB : POPULATE : 351.471 ms > Memfd 2 MiB : POPULATE_READ : 351.553 ms > Memfd 2 MiB : POPULATE_WRITE : 351.931 ms > ************************************************** > 4096 MiB MAP_SHARED: > ************************************************** > Anonymous : Read : 229.338 ms > Anonymous : Write : 478.964 ms > Anonymous : Read+Write : 234.546 ms > Anonymous : POPULATE : 161.635 ms > Anonymous : POPULATE_READ : 160.943 ms > Anonymous : POPULATE_WRITE : 252.686 ms > Memfd 4 KiB : Read : 1052.828 ms > Memfd 4 KiB : Write : 929.237 ms > Memfd 4 KiB : Read+Write : 1074.494 ms > Memfd 4 KiB : POPULATE : 915.663 ms > Memfd 4 KiB : POPULATE_READ : 915.001 ms > Memfd 4 KiB : POPULATE_WRITE : 787.388 ms > Memfd 2 MiB : Read : 353.580 ms > Memfd 2 MiB : Write : 353.197 ms > Memfd 2 MiB : Read+Write : 353.172 ms > Memfd 2 MiB : POPULATE : 353.686 ms > Memfd 2 MiB : POPULATE_READ : 353.465 ms > Memfd 2 MiB : POPULATE_WRITE : 352.776 ms > ************************************************** >=20 >=20 > --- Discussion --- >=20 > 1) With huge pages, the performance benefit is negligible with the size= s > I tried, because there are little actual page faults. Most time is spen= t > zeroing huge pages I guess. It will take quite a lot of memory to pay o= ff. >=20 > 2) In all 4k cases, the POPULATE_READ/POPULATE_WRITE variants are faste= r > than manually reading or writing from user space. >=20 >=20 > What sticks out a bit is: >=20 > 3) For MAP_SHARED on anonymous memory, it is fastest to first read and > then write memory. It's slightly faster than POPULATE_WRITE and quite a > lot faster than a simple write - what?!. It's even faster than > POPULATE_WRITE - what?! I assume with the read access we prepare a fres= h > zero page and with the write access we only have to change PTE access > rights. But why is this faster than writing directly? Okay, MADV_DONTNEED does not seem to really work on MAP_SHARED of=20 anonymous memory. If I use a fresh mmap for each and every iteration the=20 numbers make more sense: ************************************************** 4096 MiB MAP_SHARED: ************************************************** Anonymous : Read : 1054.154 ms Anonymous : Write : 924.572 ms Anonymous : Read+Write : 1075.215 ms Anonymous : POPULATE : 911.386 ms Anonymous : POPULATE_READ : 909.392 ms Anonymous : POPULATE_WRITE : 793.143 ms --=20 Thanks, David / dhildenb