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[142.162.115.133]) by smtp.gmail.com with ESMTPSA id n4sm4362113qke.30.2021.02.18.09.25.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Feb 2021 09:25:01 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1lCn2y-00B5ZE-I2; Thu, 18 Feb 2021 13:25:00 -0400 Date: Thu, 18 Feb 2021 13:25:00 -0400 From: Jason Gunthorpe To: Matthew Wilcox Cc: Andrew Morton , Mike Kravetz , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Zi Yan , Davidlohr Bueso , "Kirill A . Shutemov" , Andrea Arcangeli , Oscar Salvador , Joao Martins , stable@vger.kernel.org Subject: Re: [PATCH 1/2] hugetlb: fix update_and_free_page contig page struct assumption Message-ID: <20210218172500.GA4718@ziepe.ca> References: <20210217184926.33567-1-mike.kravetz@oracle.com> <20210217110252.185c7f5cd5a87c3f7b0c0144@linux-foundation.org> <20210218144554.GS2858050@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210218144554.GS2858050@casper.infradead.org> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D2A0D407F8F3 X-Stat-Signature: b1tnhgc6p4fdwjopi5c3cqhfeucguynd Received-SPF: none (ziepe.ca>: No applicable sender policy available) receiver=imf02; identity=mailfrom; envelope-from=""; helo=mail-qt1-f178.google.com; client-ip=209.85.160.178 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1613669093-374587 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 Thu, Feb 18, 2021 at 02:45:54PM +0000, Matthew Wilcox wrote: > On Wed, Feb 17, 2021 at 11:02:52AM -0800, Andrew Morton wrote: > > On Wed, 17 Feb 2021 10:49:25 -0800 Mike Kravetz wrote: > > > page structs are not guaranteed to be contiguous for gigantic pages. The > > > > June 2014. That's a long lurk time for a bug. I wonder if some later > > commit revealed it. > > I would suggest that gigantic pages have not seen much use. Certainly > performance with Intel CPUs on benchmarks that I've been involved with > showed lower performance with 1GB pages than with 2MB pages until quite > recently. I suggested in another thread that maybe it is time to consider dropping this "feature" If it has been slightly broken for 7 years it seems a good bet it isn't actually being used. The cost to fix GUP to be compatible with this will hurt normal GUP performance - and again, that nobody has hit this bug in GUP further suggests the feature isn't used.. Jason