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 DB03CC5478C for ; Tue, 27 Feb 2024 18:02:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6C6826B00C0; Tue, 27 Feb 2024 13:02:35 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 687976B00C1; Tue, 27 Feb 2024 13:02:35 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 53DA36B00C2; Tue, 27 Feb 2024 13:02:35 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 452EA6B00C0 for ; Tue, 27 Feb 2024 13:02:35 -0500 (EST) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 19FCB1A0C2C for ; Tue, 27 Feb 2024 18:02:35 +0000 (UTC) X-FDA: 81838353870.26.6FF8AED Received: from mail-ed1-f51.google.com (mail-ed1-f51.google.com [209.85.208.51]) by imf30.hostedemail.com (Postfix) with ESMTP id 8744A80013 for ; Tue, 27 Feb 2024 18:02:31 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=G9V42Swi; dmarc=none; spf=pass (imf30.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.51 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1709056951; a=rsa-sha256; cv=none; b=PGIdMwe3B++QREdKK59JmE78o1AAyPQTHrqmocpPPy3UJLofffIh3KhVpDAy49VVSYxkja UX3wgsxvHIguVrqqVJNt4Zs/Wg28HhUPAEw6txqn+1Sr8jHhlEY9SJdTMTXjoqc6XMTokW WDKZL1aj6i8z0QmG8u38eWQo13MknaI= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=G9V42Swi; dmarc=none; spf=pass (imf30.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.51 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1709056951; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=IS9XnkEKGp//6JjTXav355pPYCtjFbiml+eyjIEah2s=; b=Beh4mDqfbkqG0nXWrMBVU5BvLTabYjfTABWgC2T+Xxml7km7S3fjfH3hczDAmAOiO0euB6 FXwKaWinBZej1BzvXgtQm6gxZUg6rz0zTuBSJKc7PRRqqBW3HOSj2nwekn04ieXX/63U// b16mJH+yXU21/oFmFbHL+EdD7o1nmYA= Received: by mail-ed1-f51.google.com with SMTP id 4fb4d7f45d1cf-55f50cf2021so7113239a12.1 for ; Tue, 27 Feb 2024 10:02:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; t=1709056950; x=1709661750; darn=kvack.org; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=IS9XnkEKGp//6JjTXav355pPYCtjFbiml+eyjIEah2s=; b=G9V42SwiBKd2MmhXMaEdhtsoH76UNOQBeMBU4QCFwerhbwuzSnfp+ziHfzhZ/Wrpgs sYybLGkHnrAScMvzTjRgh9aP4rx1zLgvl7gSeBTx/7TQ7eyzVt9s+t4A6mDH3EHYXFoh bauFDj89mIYE5f3/amhjYwVrfZk4mZ1SNcZRI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1709056950; x=1709661750; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=IS9XnkEKGp//6JjTXav355pPYCtjFbiml+eyjIEah2s=; b=EuFQruBLS7280sjACAPichwCLdMGnQnjc3jIJkLCOyOHOzFKxpZvaFiN2TfQNBqbcd 9beZMYjZWoul8RYPj2uh0ONb+indu9pDl7vNtaclIs/4+TuWYkuRYrYRKHLau2YNOZ/p shFuB35ueSxnvwAZUqkFQo0V3+H01NCyo8XvxZdMnnY2Voui1LtLDG7OvhKV9pcI7sic DXm4To9eSYNp7wTpVZrwOI3kvoS7Kd1KVpOvlUrQy55CYSt38q1OyVEgOM1XJU04ezfn vYffiI+vNm1GUFBDfg10vFCnohbvHLT9bXN743pmPfxN57Uz/r4hAzRFzvOkTl2GZa8B MQuQ== X-Forwarded-Encrypted: i=1; AJvYcCUQfCuBy52O1l5d+IvfpozDkLMC+y4CrX4q4oSLk76PsuobWd/KlieRs/qY+HWoKUb/r+3swdtKQWSM7uU2p5/1toE= X-Gm-Message-State: AOJu0Yw/I3KRgClMRlI6UcPxDo1TGkYlJrrrvZL4DU8hiHqG125TC+WA m0b2y28XblIu4dLOyas7xFEmvZDbyd1Xwh9YgO2gDs1dyouNa5SLsEP+DoXxfBeX5lwMKIh0iXu TBNiibQ== X-Google-Smtp-Source: AGHT+IF1oOQaxC/d6SUX+uJc5yDUpGphTEtOtQAEwf5bz21RFdU1KIj4ks+lfPHnYA7zXhcf9ueHug== X-Received: by 2002:aa7:cb45:0:b0:564:e0af:8b11 with SMTP id w5-20020aa7cb45000000b00564e0af8b11mr7302667edt.32.1709056949775; Tue, 27 Feb 2024 10:02:29 -0800 (PST) Received: from mail-ed1-f49.google.com (mail-ed1-f49.google.com. [209.85.208.49]) by smtp.gmail.com with ESMTPSA id ec31-20020a0564020d5f00b0056650cd0156sm307458edb.66.2024.02.27.10.02.28 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Feb 2024 10:02:29 -0800 (PST) Received: by mail-ed1-f49.google.com with SMTP id 4fb4d7f45d1cf-55a035669d5so8139247a12.2 for ; Tue, 27 Feb 2024 10:02:28 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCWxpWVFMgrrHMQZNLOkXqb7YMgG4IrXf+7JJJT4xlPsGVlpvuXlLznWKUBlQKZeVcgwMJWcP5YltiAoTjcax5LoodQ= X-Received: by 2002:a17:906:d04c:b0:a3f:adcf:7f58 with SMTP id bo12-20020a170906d04c00b00a3fadcf7f58mr6925951ejb.21.1709056948649; Tue, 27 Feb 2024 10:02:28 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Tue, 27 Feb 2024 10:02:11 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [LSF/MM/BPF TOPIC] Measuring limits and enhancing buffered IO To: Kent Overstreet Cc: Al Viro , Matthew Wilcox , Luis Chamberlain , lsf-pc@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm , Daniel Gomez , Pankaj Raghav , Jens Axboe , Dave Chinner , Christoph Hellwig , Chris Mason , Johannes Weiner Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 8744A80013 X-Stat-Signature: n8snbb6j6rr6w3nhsqkghj4c1jes9zqg X-HE-Tag: 1709056951-58251 X-HE-Meta: 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 FH7x2Nzy nNFBTtne5xbCCIJnAf7NDqADkkkF8/NHIr5YbUga1lIWidIawERTT23R5FwJwVRXgc1koCnwwbm9w58Bn2RFmUT0uJnpI11ea74JN9SZ5OW62z4hxcciBRPot38u5patIM/TsrqLa6iqCiaVg5u8MkOebVEYSLeZyEk8d0NZYW4EcdlBABGsEJoCZ1abJPUbcnx0U2lFJo9yCDutay6pJrvipdshC50IokSlGSNyNfHAaen5ETOHkf93BQ5S80o2HuDZyMxY3c3+IEc8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000017, 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 Tue, 27 Feb 2024 at 09:20, Kent Overstreet wrote: > > fio \ > --group_reporting \ [..] Ok, I have to say that my kernel profile looks very nice with that patch. It all looks almost perfect, and the main big spike in the profile is the inevitable "clac/stac" pair around the user copy because my old threadripper just ends up not doing that very well. Of course, I disable all the mitigations for my profiling runs, because not doing that is just too depressing and any real kernel issues that we can do something about get hidden by the noise introduced by the mitigations. So my profiles are entirely artificial in that sense (I tell myself that it's what future CPU's will look like and that it's ok. Then I cry myself to sleep). I'm not going to push that patch of mine - I still suspect that doing this all under RCU with page faults optimistically disabled would be a much nicer model and work for bigger areas - but I don't hate the patch either, and if somebody else wants to push it, I'm ok with it. I can't actually think of any real load that does a lot of small reads. Willy's odd customer not-withstanding. Linus