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Tue, 9 Oct 2018 16:06:33 +0000 (GMT) Received: from eusmgms1.samsung.com (unknown [182.198.249.179]) by eusmtrp1.samsung.com (KnoxPortal) with ESMTP id 20181009160633eusmtrp1a0edac6d8c9fe477ba05125cfa0448de~b-GGSgyLO1335813358eusmtrp1-; Tue, 9 Oct 2018 16:06:33 +0000 (GMT) X-AuditID: cbfec7f2-5c9ff70000001159-5b-5bbcd20a203f Received: from eusmtip1.samsung.com ( [203.254.199.221]) by eusmgms1.samsung.com (EUCPMTA) with SMTP id B7.B6.04284.902DCBB5; Tue, 9 Oct 2018 17:06:33 +0100 (BST) Received: from [106.120.51.20] (unknown [106.120.51.20]) by eusmtip1.samsung.com (KnoxPortal) with ESMTPA id 20181009160633eusmtip186da2c5d513a4633537dda57c94e61d6~b-GF6nam01919619196eusmtip14; Tue, 9 Oct 2018 16:06:33 +0000 (GMT) Subject: Re: [PATCH] Doc: lockdep: add information about performance impact To: Peter Zijlstra Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, b.zolnierkie@samsung.com, mingo@redhat.com, will.deacon@arm.com, corbet@lwn.net From: Lukasz Luba Date: Tue, 9 Oct 2018 18:06:31 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181009154359.GB5728@hirez.programming.kicks-ass.net> Content-Language: en-US Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrPKsWRmVeSWpSXmKPExsWy7djPc7pcl/ZEGxw8pWKxccZ6VosnB9oZ LTY9vsZqcXnXHDaLSwcWMFkc7z3AZPHy4wkWB3aPNfPWMHpsXqHlsXlJvcfivsmsHu/3XWXz 6NuyitHj8ya5APYoLpuU1JzMstQifbsErozt73qZC36zVrQenMvawHidpYuRk0NCwERi07uz QDYXh5DACkaJi3v3soMkhAS+MEpsOOIOkfjMKPH9+QdWmI6N754zQySWAxVNPc4C0fGWUeL+ vswuRg4OYQFviQnPmUDCIgKaEivb7rOB1DMLzGaUmHBgEyNIDZuAnsSOVYUgNSwCKhK39p4A GyMqECFx5MFCRhCbV0BQ4uTMJ2BxTgEXia7n85lBbGYBcYlbT+YzQdjyEtvfzgG7R0JgH7vE zRPnoJrLJDZvnQP1povEkfv3mCFsYYlXx7ewQ9gyEqcn90DVFEuc7VjFBmHXSLSf3AFVYy1x +PhFVpCbmYGeWb9LHyLsKLHs9VsmkLCEAJ/EjbeCEOfwSUzaNp0ZIswr0dEmBFGtIbGl5wIT hC0msXzNNPYJjEqzkDw5C8ljs5A8Ngth7wJGllWM4qmlxbnpqcWGeanlesWJucWleel6yfm5 mxiByej0v+OfdjB+vZR0iFGAg1GJh7fhwp5oIdbEsuLK3EOMEhzMSiK8ott3RQvxpiRWVqUW 5ccXleakFh9ilOZgURLnXTZvY7SQQHpiSWp2ampBahFMlomDU6qBkSfT89JLhvKE8CqzGzbH jP+HvLy6aeviD+f2Pa9pXho79X1U1PaIRfrWS75vfXOB+c2eMDGl/2b8XcGCvGFNd3Xr7pXm r17NaHvIxyw9qzvGtD1Wo/fIVo11y5L+MMy6J53d97h9At9hq6aODyuS7rG/3H9Y2fL60WCN xfsuvI78O3/BrMOZW5VYijMSDbWYi4oTAULZGyFCAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrKIsWRmVeSWpSXmKPExsVy+t/xu7qcl/ZEG7Q+VLbYOGM9q8WTA+2M FpseX2O1uLxrDpvFpQMLmCyO9x5gsnj58QSLA7vHmnlrGD02r9Dy2Lyk3mNx32RWj/f7rrJ5 9G1ZxejxeZNcAHuUnk1RfmlJqkJGfnGJrVK0oYWRnqGlhZ6RiaWeobF5rJWRqZK+nU1Kak5m WWqRvl2CXsb2d73MBb9ZK1oPzmVtYLzO0sXIySEhYCKx8d1z5i5GLg4hgaWMEv87JjNDJMQk Ju3bzg5hC0v8udbFBlH0mlHi6O1+oG4ODmEBb4kJz5lAakQENCVWtt0Hq2EWmM0o0X5tLlRD C5PE+r8dzCANbAJ6EjtWFYI08Aq4SdzdtIURxGYRUJG4tfcE2EWiAhESq5e/YIWoEZQ4OfMJ WJxTwEWi6/l8sOOYBcwk5m1+CGWLS9x6Mp8JwpaX2P52DvMERqFZSNpnIWmZhaRlFpKWBYws qxhFUkuLc9Nziw31ihNzi0vz0vWS83M3MQKjcNuxn5t3MF7aGHyIUYCDUYmHt+HCnmgh1sSy 4srcQ4wSHMxKIryi23dFC/GmJFZWpRblxxeV5qQWH2I0BXpuIrOUaHI+MEHklcQbmhqaW1ga mhubG5tZKInznjeojBISSE8sSc1OTS1ILYLpY+LglGpgTA9OuPL9rdvGh+/WGPkvjdlm0vgk +s29jJi7G7syV1kvmB/JGX1YO2frs/S6T7c+7OeRUFpY4fEleo6Cq/W89VbSp2V67TdvWn/W v63p1FHvOeWsS/8kcdYkro9Ilrwwr7an/9nr6s6ORNXPTsl9u1OStSx+7xZs6Kn6V/yvYkVA +q0jO/p2K7EUZyQaajEXFScCANfo5R7YAgAA Message-Id: <20181009160633eucas1p1a597c95256e64bf01de32366afdc59dd~b-GGjOUFN2705527055eucas1p1b@eucas1p1.samsung.com> X-CMS-MailID: 20181009160633eucas1p1a597c95256e64bf01de32366afdc59dd X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20181009153935eucas1p2dec146575ed5fefd4a0b2b6cb9bac056 X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20181009153935eucas1p2dec146575ed5fefd4a0b2b6cb9bac056 References: <20181009153935eucas1p2dec146575ed5fefd4a0b2b6cb9bac056~b_ujkjRd31303013030eucas1p2C@eucas1p2.samsung.com> <20181009154359.GB5728@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On 10/09/2018 05:43 PM, Peter Zijlstra wrote: > On Tue, Oct 09, 2018 at 05:39:27PM +0200, Lukasz Luba wrote: >> This patch add some warning related to performance drop. >> It should be mentioned that this is not for free >> and the platfrom resources (cache, bus interconnect, etc.) >> will be used more frequently. > > To me this reads a bit like: water is wet. > > Is this really needed? > > Well, it would be good to know what is the performance drop (10% or 20% or x3 times) when you are enabling different debug options. I have spent some time analyzing these cache and bus strange behavior. Now the developers would know that LOCKDEP might cause constant trashing of your cache in some use cases. Regards, Lukasz Luba