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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 12439C43613 for ; Fri, 21 Jun 2019 23:55:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D4C3020821 for ; Fri, 21 Jun 2019 23:55:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZpPFzcp3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726206AbfFUXz0 (ORCPT ); Fri, 21 Jun 2019 19:55:26 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:35890 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726045AbfFUXz0 (ORCPT ); Fri, 21 Jun 2019 19:55:26 -0400 Received: by mail-pg1-f193.google.com with SMTP id f21so4102596pgi.3; Fri, 21 Jun 2019 16:55:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:subject:to:cc:references:in-reply-to:mime-version :user-agent:message-id:content-transfer-encoding; bh=x9bZV3T0S6eNYo6IXHrd+kECvmTbbAucaYzxDYrbdeI=; b=ZpPFzcp36+Hh5jye0ZKjtgJ550NYI096FfX2rcFyQ99LOi8SMis6xF/dheI3yxj7vn TBGcbHMLdJQh068I90oszy1lxCnmI5g4KVT7DQMh+oL+mOljJTN2ljZWYTmOt23yVg2h LdyqXTNKqxAmKaI+JKi19peuQtNFJ/A6jfkfKGStmgPKTkapA12DT/MDePfRHMwpeCd2 tgrx+S6ckAPgkEN6TA/783NZNMh/U4UZX0873+4sMF+NwUUbApR86gBQBtLXNIwieoaL GIkk0MteisbTCO2dsnPaZ8Qv7rsQ8XF4reLwhY4yUxl1spYYF0SWL0LStYP/hWINYrnP HtFA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:subject:to:cc:references:in-reply-to :mime-version:user-agent:message-id:content-transfer-encoding; bh=x9bZV3T0S6eNYo6IXHrd+kECvmTbbAucaYzxDYrbdeI=; b=GGNoFY7IxmNq7LxYvUPVz0h2o4fpA+vbxa7Nj05rw1/Pn6zib9rJdu2FsnenFXDHgb BFnh/oNW0lMkL2ROFBxYynlVkFS96Zvj8YoizUWm4sJwQIyBh8IKkTdaSSJrSvfH+Ob/ NwhMJfCGpiflg06z4gCpXJKK7HWXVei0BJE9GVtrQphnXWO+vliensRk+pCANegDv6c1 5TRna33KE10BgrrHBVxw3anYDQjd9VoCJ6DWpj3CVHXcLZ5isULeuGTjiuvsMjkJSHf3 /MGEhvRTbuxXZK4FNNB5RWQcU58wpZc+9taJlo6U2eR9kuiYZqv0NcWX9PEFAML9Et3o DCUA== X-Gm-Message-State: APjAAAXlD9qYDxECqZ+vzdNqlJD2477W1qJqG3LGubbrsbcngxR8bHDP nRPHfQJgxIhPvhDUbJunwWE= X-Google-Smtp-Source: APXvYqyqRRpjMOtRudskKnzHE+bVq170qVap7+EY5kc6j/qI6uUR3V4Zstw2KCShBoXYwoTuoCwbAg== X-Received: by 2002:a63:545c:: with SMTP id e28mr4210785pgm.374.1561161325219; Fri, 21 Jun 2019 16:55:25 -0700 (PDT) Received: from localhost ([1.144.144.251]) by smtp.gmail.com with ESMTPSA id 85sm4623425pfv.130.2019.06.21.16.55.23 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 21 Jun 2019 16:55:24 -0700 (PDT) Date: Sat, 22 Jun 2019 09:55:09 +1000 From: Nicholas Piggin Subject: Re: [PATCH 16/16] mm: pass get_user_pages_fast iterator arguments in a structure To: Christoph Hellwig , Linus Torvalds Cc: Andrey Konovalov , Benjamin Herrenschmidt , Rich Felker , "David S. Miller" , James Hogan , Khalid Aziz , Linux List Kernel Mailing , linux-mips@vger.kernel.org, Linux-MM , linuxppc-dev@lists.ozlabs.org, Linux-sh list , Michael Ellerman , Paul Burton , Paul Mackerras , sparclinux@vger.kernel.org, the arch/x86 maintainers , Yoshinori Sato References: <20190611144102.8848-1-hch@lst.de> <20190611144102.8848-17-hch@lst.de> <1560300464.nijubslu3h.astroid@bobo.none> <1561032202.0qfct43s2c.astroid@bobo.none> <20190621081501.GA17718@lst.de> In-Reply-To: <20190621081501.GA17718@lst.de> MIME-Version: 1.0 User-Agent: astroid/0.14.0 (https://github.com/astroidmail/astroid) Message-Id: <1561160786.mradw6fg2v.astroid@bobo.none> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Christoph Hellwig's on June 21, 2019 6:15 pm: > On Thu, Jun 20, 2019 at 10:21:46AM -0700, Linus Torvalds wrote: >> Hmm. Honestly, I've never seen anything like that in any kernel profiles= . >>=20 >> Compared to the problems I _do_ see (which is usually the obvious >> cache misses, and locking), it must either be in the noise or it's >> some problem specific to whatever CPU you are doing performance work >> on? >>=20 >> I've occasionally seen pipeline hiccups in profiles, but it's usually >> been either some serious glass jaw of the core, or it's been something >> really stupid we did (or occasionally that the compiler did: one in >> particular I remember was how there was a time when gcc would narrow >> stores when it could, so if you set a bit in a word, it would do it >> with a byte store, and then when you read the whole word afterwards >> you'd get a major pipeline stall and it happened to show up in some >> really hot paths). >=20 > I've not seen any difference in the GUP bench output here ar all. >=20 > But I'm fine with skipping this patch for now, I have a potential > series I'm looking into that would benefit a lot from it, but we > can discusss it in that context and make sure all the other works gets in > in time. >=20 If you can, that would be good. I don't like to object based on handwaving so I'll see if I can find any benchmarks that will give better confidence. Those old TPC-C tests were good, and there was some DB2 workload that was the reason I added gup fast in the first place. I'll do some digging. Thanks, Nick =