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[209.85.220.65]) by mx.google.com with SMTPS id d6sor21494768pfd.59.2019.07.22.10.50.29 for (Google Transport Security); Mon, 22 Jul 2019 10:50:29 -0700 (PDT) Received-SPF: pass (google.com: domain of linux.bhar@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=n1SlHMSo; spf=pass (google.com: domain of linux.bhar@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=linux.bhar@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=/LORfxhH4cPCyhMYt6N2Wj9cKNe2qt9hnR1X3sMowdQ=; b=n1SlHMSojQt0P7r4oOYQHnxtZpqyOPYp6kEQKFu9QtR2xjN41TFnIsvdRCN+aCtxPl 4k3OiuK9FPft3Q4bXlV4mmO1yp2bxWNtUE1rsSa4pnvA9Bs7PR2Xr6ODcmZR6dvZnF7W tbm6cXf5r+0tUaqTxfRb7v8NZgjzLCiDBMWZFhhYTf7yPXHdIVEoVrJmzknZF4BL/M19 iDyHcbXXPQjpRFq74i/6P8XHmdaBtL2B0x5StS3f+oxCxdIOUQwRKblPX4SXmXRlUO9z ta+dSgEQrvq1LWUSPv600HB+SGa25QRnyYIYPcLSw9vXg8nvthD5S/omzUjpaEJSmOqU nesQ== X-Google-Smtp-Source: APXvYqz1ZJ0Sw8KehKmYgjC5235A6lpjGgfo2wFuW+DCqMntVVX0am9/kqG+nW9cfKzlFJdJFG+tNg== X-Received: by 2002:aa7:9118:: with SMTP id 24mr1343927pfh.56.1563817829565; Mon, 22 Jul 2019 10:50:29 -0700 (PDT) Received: from bharath12345-Inspiron-5559 ([103.110.42.33]) by smtp.gmail.com with ESMTPSA id t2sm35502130pgo.61.2019.07.22.10.50.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Jul 2019 10:50:29 -0700 (PDT) Date: Mon, 22 Jul 2019 23:20:22 +0530 From: Bharath Vedartham To: William Kucharski Cc: arnd@arndb.de, sivanich@sgi.com, gregkh@linuxfoundation.org, ira.weiny@intel.com, jhubbard@nvidia.com, jglisse@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 2/3] sgi-gru: Remove CONFIG_HUGETLB_PAGE ifdef Message-ID: <20190722175022.GB12278@bharath12345-Inspiron-5559> References: <1563724685-6540-1-git-send-email-linux.bhar@gmail.com> <1563724685-6540-3-git-send-email-linux.bhar@gmail.com> <1BA84A99-4EB5-4520-BFBD-CD60D5B7AED9@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1BA84A99-4EB5-4520-BFBD-CD60D5B7AED9@oracle.com> User-Agent: Mutt/1.5.24 (2015-08-30) 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 Sun, Jul 21, 2019 at 09:20:38PM -0600, William Kucharski wrote: > I suspect I'm being massively pedantic here, but the comments for atomic_pte_lookup() note: > > * Only supports Intel large pages (2MB only) on x86_64. > * ZZZ - hugepage support is incomplete > > That makes me wonder how many systems using this hardware are actually configured with CONFIG_HUGETLB_PAGE. > > I ask as in the most common case, this is likely introducing a few extra instructions and possibly an additional branch to a routine that is called per-fault. > > So the nit-picky questions are: > > 1) Does the code really need to be cleaned up in this way? > > 2) If it does, does it make more sense (given the way pmd_large() is handled now in atomic_pte_lookup()) for this to be coded as: > > if (unlikely(is_vm_hugetlb_page(vma))) > *pageshift = HPAGE_SHIFT; > else > *pageshift = PAGE_SHIFT; > > In all likelihood, these questions are no-ops, and the optimizer may even make my questions completely moot, but I thought I might as well ask anyway. > That sounds reasonable. I am not really sure as to how much of an improvement it would be, the condition will be evaluated eitherways AFAIK? Eitherways, the ternary operator does not look good. I ll make a version 2 of this. > > On Jul 21, 2019, at 9:58 AM, Bharath Vedartham wrote: > > > > is_vm_hugetlb_page has checks for whether CONFIG_HUGETLB_PAGE is defined > > or not. If CONFIG_HUGETLB_PAGE is not defined is_vm_hugetlb_page will > > always return false. There is no need to have an uneccessary > > CONFIG_HUGETLB_PAGE check in the code. > > > > Cc: Ira Weiny > > Cc: John Hubbard > > Cc: Jérôme Glisse > > Cc: Greg Kroah-Hartman > > Cc: Dimitri Sivanich > > Cc: Arnd Bergmann > > Cc: linux-kernel@vger.kernel.org > > Cc: linux-mm@kvack.org > > Signed-off-by: Bharath Vedartham > > --- > > drivers/misc/sgi-gru/grufault.c | 11 +++-------- > > 1 file changed, 3 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c > > index 61b3447..75108d2 100644 > > --- a/drivers/misc/sgi-gru/grufault.c > > +++ b/drivers/misc/sgi-gru/grufault.c > > @@ -180,11 +180,8 @@ static int non_atomic_pte_lookup(struct vm_area_struct *vma, > > { > > struct page *page; > > > > -#ifdef CONFIG_HUGETLB_PAGE > > *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > -#else > > - *pageshift = PAGE_SHIFT; > > -#endif > > + > > if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0) > > return -EFAULT; > > *paddr = page_to_phys(page); > > @@ -238,11 +235,9 @@ static int atomic_pte_lookup(struct vm_area_struct *vma, unsigned long vaddr, > > return 1; > > > > *paddr = pte_pfn(pte) << PAGE_SHIFT; > > -#ifdef CONFIG_HUGETLB_PAGE > > + > > *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > > -#else > > - *pageshift = PAGE_SHIFT; > > -#endif > > + > > return 0; > > > > err: > > -- > > 2.7.4 > > >