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Wed, 3 Feb 2021 12:44:14 +0000 Received: from EX13MTAUEE002.ant.amazon.com (10.43.62.24) by EX13D07UWB004.ant.amazon.com (10.43.161.196) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 3 Feb 2021 12:44:13 +0000 Received: from 8c85908914bf.ant.amazon.com (10.1.212.23) by mail-relay.amazon.com (10.43.62.224) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Wed, 3 Feb 2021 12:44:09 +0000 From: Gal Pressman To: CC: , , , , , , , , , , , , , , , , , Subject: Re: [PATCH 1/4] mm: Trial do_wp_page() simplification Date: Wed, 3 Feb 2021 14:43:58 +0200 Message-ID: <20210203124358.59017-1-galpress@amazon.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210202171327.GN4718@ziepe.ca> References: <20210202171327.GN4718@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: quoted-printable 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, Feb 02, 2021 at 12:05:36PM -0500, Peter Xu wrote: >=20 >> > Gal, you could also MADV_DONTFORK this range if you are explicitly >> > allocating them via special mmap. >>=20 >> Yeah I wanted to mention this one too but I just forgot when reply: th= e issue >> thread previously pasted smells like some people would like to drop >> MADV_DONTFORK, but if it's able to still be applied I don't know why >> not.. >=20 > I want to drop the MADV_DONTFORK for dynamic data memory allocated by > the application layers (eg with malloc) without knowledge of how they > will be used. >=20 > This case is a buffer internal to the communication system that we > know at allocation time how it will be used; so an explicit, > deliberate, MADV_DONTFORK is fine We are referring to libfabric's bounce buffers, correct? Libfabric could be considered as the "app" here, it's not clear why these buffers should be DONTFORK'd before ibv_reg_mr() but others don't. Anyway, it should be simple enough to madvise them after allocation, alth= ough I think it's part of libfabric's generic code (which isn't necessarily used= on top of rdma-core). I'll take this discussion with the libfabric guys. Thanks Peter and Jason.