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[195.135.220.15]) by mx.google.com with ESMTPS id f14si768289eja.65.2019.02.14.00.33.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Feb 2019 00:33:52 -0800 (PST) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id DAF7FACA2; Thu, 14 Feb 2019 08:33:51 +0000 (UTC) Date: Thu, 14 Feb 2019 09:33:50 +0100 From: Michal Hocko To: Andrew Morton Cc: keith.busch@intel.com, keescook@chromium.org, dave.hansen@linux.intel.com, dan.j.williams@intel.com, linux-mm@kvack.org Subject: Re: + mm-shuffle-default-enable-all-shuffling.patch added to -mm tree Message-ID: <20190214083350.GY4525@dhcp22.suse.cz> References: <20190206200254.bcdZQ%akpm@linux-foundation.org> <20190212085428.GP15609@dhcp22.suse.cz> <20190212134622.9e685e9a955915d1a058ea99@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190212134622.9e685e9a955915d1a058ea99@linux-foundation.org> User-Agent: Mutt/1.10.1 (2018-07-13) 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 12-02-19 13:46:22, Andrew Morton wrote: > On Tue, 12 Feb 2019 09:54:28 +0100 Michal Hocko wrote: > > > On Wed 06-02-19 12:02:54, Andrew Morton wrote: > > > From: Dan Williams > > > Subject: mm/shuffle: default enable all shuffling > > > > > > Per Andrew's request arrange for all memory allocation shuffling code to > > > be enabled by default. > > > > > > The page_alloc.shuffle command line parameter can still be used to disable > > > shuffling at boot, but the kernel will default enable the shuffling if the > > > command line option is not specified. > > > > > > Link: http://lkml.kernel.org/r/154943713572.3858443.11206307988382889377.stgit@dwillia2-desk3.amr.corp.intel.com > > > Signed-off-by: Dan Williams > > > Cc: Kees Cook > > > Cc: Michal Hocko > > > Cc: Dave Hansen > > > Cc: Keith Busch > > > > > > Signed-off-by: Andrew Morton > > > > I hope this is mmotm only thing and even then, is this really > > something we want for linux-next? There are people doing testing and > > potentially performance testing on that tree. Do we want to invalidate > > all that work? I can see some argument about a testing coverage but do > > we really need it for the change like this? The randomization is quite > > simple to review and I assume Dan has given this good testing before > > submition. > > Please see the mailing list discussion. Without this patch the feature > is likely to end up in mainline with next to no testing other than Dan's. Isn't that the case for most of the functionality behind CONFIG_$FOO that doesn't get enabled by default? It is not that I care too much but I find this way of argumentation strange. It is the submitter to make sure the feature is tested properly and reviewers should make sure the overall design and implementation makes sense. I do not see reason why all users of linux-next should be a guinea pigs without knowing that. -- Michal Hocko SUSE Labs