From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id B1F536B0062 for ; Thu, 17 Dec 2009 01:24:24 -0500 (EST) From: "Shilimkar, Santosh" Date: Thu, 17 Dec 2009 11:54:10 +0530 Subject: RE: CPU consumption is going as high as 95% on ARM Cortex A8 Message-ID: References: <19F8576C6E063C45BE387C64729E73940449F43857@dbde02.ent.ti.com> In-Reply-To: <19F8576C6E063C45BE387C64729E73940449F43857@dbde02.ent.ti.com> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org To: "Hiremath, Vaibhav" , "linux@arm.linux.org.uk" Cc: "linux-mm@kvack.org" , "linux-omap@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" List-ID: > -----Original Message----- > From: linux-arm-kernel-bounces@lists.infradead.org [mailto:linux-arm-kern= el- > bounces@lists.infradead.org] On Behalf Of Hiremath, Vaibhav > Sent: Thursday, December 17, 2009 11:09 AM > To: linux@arm.linux.org.uk > Cc: linux-mm@kvack.org; linux-omap@vger.kernel.org; linux-arm-kernel@list= s.infradead.org > Subject: CPU consumption is going as high as 95% on ARM Cortex A8 >=20 > Hi, >=20 > I am seeing some strange behavior while accessing buffers through User Sp= ace (mapped using mmap call) >=20 > Background :- > ------------ > Platform - TI AM3517 > CPU - ARM Cortex A8 >=20 > root@am3517-evm:~# > root@am3517-evm:~# cat /proc/cpuinfo > Processor : ARMv7 Processor rev 7 (v7l) > BogoMIPS : 499.92 > Features : swp half thumb fastmult vfp edsp neon vfpv3 > CPU implementer : 0x41 > CPU architecture: 7 > CPU variant : 0x1 > CPU part : 0xc08 > CPU revision : 7 > Hardware : OMAP3517/AM3517 EVM > Revision : 0020 > Serial : 0000000000000000 > root@omap3517-evm:~# >=20 >=20 > Issue/Usage :- > ------------- > The V4l2-Capture driver captures the data from video decoder into buffer = and the application does > some processing on this buffer. The mmap implementation can be found at d= rivers/media/video/videobuf- > dma-contig.c, function__videobuf_mmap_mapper(). >=20 > Observation - > The CPU consumption goes as high as 95% on read buffer operation, please = note that write operation on > these buffers also gives 60-70% CPU consumption. (Using memcpy/memset API= 's for read and write > operation). >=20 > Some more inputs :- > ------------------ > - If I specify PAGE_READONLY or PAGE_SHARED (actual flag is L_PTE_USER) w= hile mapping the buffer to > UserSpace in mmap system call, the CPU consumption goes down to expected = value (20-27%). > Then I reached till the function cpu_v7_set_pte_ext, where we are configu= ring level 2 translation > table entries, which makes use of these flags. >=20 > - Below is the value of r0, r1 and r2 register (ptep, pteval, ext) in bot= h the cases - >=20 >=20 > Without PAGE_READONLY/PAGE_SHARED >=20 > ptep - cfb5de10, pte - 8d200383, ext - 800 > ptep - cfb5de14, pte - 8d201383, ext - 800 Which kernel version is this? Can you please also give values of PRRR, NMRR= and SCTLR=20 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org