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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id AD0DDC43334 for ; Wed, 22 Jun 2022 14:21:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 32C968E00B7; Wed, 22 Jun 2022 10:21:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2DBFC8E00AB; Wed, 22 Jun 2022 10:21:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1CC0B8E00B7; Wed, 22 Jun 2022 10:21:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 09E3D8E00AB for ; Wed, 22 Jun 2022 10:21:49 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id D061C35311 for ; Wed, 22 Jun 2022 14:21:48 +0000 (UTC) X-FDA: 79606085496.14.885EC98 Received: from mail.skyhub.de (unknown [5.9.137.197]) by imf30.hostedemail.com (Postfix) with ESMTP id 569BD800A0 for ; Wed, 22 Jun 2022 14:21:40 +0000 (UTC) Received: from zn.tnic (p200300ea974657a8329c23fffea6a903.dip0.t-ipconnect.de [IPv6:2003:ea:9746:57a8:329c:23ff:fea6:a903]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id F09431EC0432; Wed, 22 Jun 2022 16:21:12 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1655907673; 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=his6AREgNwUOcgnQ+a3chr9iKtHV7zPpU83pOda0rZQ=; b=d1/sLmZ4NX6wGx0Z24i7Bcf25r5hyIfj758idWb0wuuQg0nIG/+4YsW++zKG0OdrO18xc3 cMkjvsgqwf3CutrCQ9oXHllj8GIGRsRkQrk5o2jffLoFlKdjYAZ7q/mH9VGtbXvDUjyErm O1lnqYbK5LuQCQ/Smuj0Rxtxm844qFE= Date: Wed, 22 Jun 2022 16:21:08 +0200 From: Borislav Petkov To: Linus Torvalds Cc: Mark Hemment , Andrew Morton , the arch/x86 maintainers , Peter Zijlstra , patrice.chotard@foss.st.com, Mikulas Patocka , Lukas Czerner , Christoph Hellwig , "Darrick J. Wong" , Chuck Lever , Hugh Dickins , patches@lists.linux.dev, Linux-MM , mm-commits@vger.kernel.org, Mel Gorman Subject: Re: [PATCH] x86/clear_user: Make it faster Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 569BD800A0 X-Rspam-User: Authentication-Results: imf30.hostedemail.com; dkim=temperror ("DNS error when getting key") header.d=alien8.de header.s=dkim header.b="d1/sLmZ4"; spf=temperror (imf30.hostedemail.com: error in processing during lookup of bp@alien8.de: DNS error) smtp.mailfrom=bp@alien8.de; dmarc=temperror reason="query timed out" header.from=alien8.de (policy=temperror) X-Rspamd-Server: rspam08 X-Stat-Signature: tzrb7589rie6c5tzpyz6i88p7kqpp47w X-HE-Tag: 1655907700-859732 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 Tue, May 24, 2022 at 02:32:36PM +0200, Borislav Petkov wrote: > I still need to run it on production Icelake and that is kinda being > delayed due to server room cooling issues (don't ask ;-\). So I finally got a production level ICL-X: [ 0.220822] smpboot: CPU0: Intel(R) Xeon(R) Gold 6336Y CPU @ 2.40GHz (family: 0x6, model: 0x6a, stepping: 0x6) and frankly, this looks really weird: clear_user_original: Amean: 19679.4 (Sum: 13652560764, samples: 693750) Amean: 19743.7 (Sum: 13693470604, samples: 693562) (I ran it twice just to be sure.) ERMS: Amean: 20374.3 (Sum: 13910601024, samples: 682752) Amean: 20453.7 (Sum: 14186223606, samples: 693576) FSRM: Amean: 20458.2 (Sum: 13918381386, sample s: 680331) so either that particular box is weird or Icelake really is slower wrt FSRM or I've fat-fingered it somewhere. But my measuring is as trivial as: static __always_inline unsigned long clear_user(void __user *to, unsigned long n) { if (access_ok(to, n)) { unsigned long start, end, ret; start = rdtsc_ordered(); ret = __clear_user(to, n); end = rdtsc_ordered(); trace_printk("to: 0x%lx, size: %ld, cycles: %lu\n", (unsigned long)to, n, end - start); return ret; } return n; } so if anything I don't see what the problem could be... Hmm. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette